texts: Order of nucleophilicity of ammonia, hydrazine and hydroxylamine

texts:
I was reading about nucleophilicity and basic strength orders. I came across this interesting set of three compounds $\ce{NH3},$ $\ce{N2H4}$ and $\ce{NH2OH}$ where I am not able to apply the rules I have learnt.
The correct order of basic strength is given to be:

$K_\mathrm b$ value: $\ce{NH3} > \ce{N2H4} > \ce{NH2OH}$

The rules I know are:

If the donor atom is same, then order of nucleophilicity is same as the order of basicity.
Alpha effect: if the adjacent atom attached to the donating atom has lone pair of electrons, then nucleophilicity is enhanced.

When I try to conclude the nucleophilicity order, I am getting contradicting results with the above rules. Also, I wonder whether the −I effect due to the presence of highly electronegative atom may have a role to play.
So, what is the correct order of nucleophilicity of $\ce{NH3},$ $\ce{N2H4}$ and $\ce{NH2OH}?$
Is it theoretically possible to conclude the correct order based on deciding which factor will dominate in a given situation?
CLARIFICATION:
My doubt is pertaining to specifically these three compounds.Many have said that this question is a duplicate of Is there a general consensus on the causes of the alpha-effect?
But, I am not able to get the order of nucleophilicity that I need from the answers to that question.I am not able to find the information on order of nucleophilicity of these three compounds in the books I use.So, it would be helpful if someone clarifies the position of $\ce{NH2OH}$ in this.


texts:
My textbook states

  "Cubic crystals contain four three-fold axes, converting the ellipsoid to a sphere."

What indeed is the ellipsoid and sphere in the lattice? I know the meaning of three fold axes but unable to figure out what and how ellipsoid is converted to sphere.


texts: PEG (polyethylene glycol) and ITO (indium tin oxide)

texts:
The binding of proteins to an ITO surface can be prevented by coating it with PEG groups (polyethylene glycol). PEG-silane is used to create the coating.

can somebody help with:

Why does PEG-silane bind to ITO (indium tin oxide)? and how? (which bond etc.)
Why does PEG repel proteins?
Are there better coatings to use to repel proteins?


texts:
Inspired by this article, I've been looking at using metallic hydrogen as a rocket fuel using CEARUN. I'm looking at diluting the atomic hydrogen with liquid methane to reduce the chamber temperature to something that could be handled using known materials. The reaction that powers the rocket would be $\ce{H^. + H^. -> H2}$. I used a mixture ratio of 4.5 mass units of liquid methane to 1 mass unit of atomic hydrogen. I got an ISP of ~760-780 seconds at reasonable chamber temperatures (3650 kelvin). The main exhaust products in terms of 'molar fractions' are as follows: $\ce{H2} = \pu{79.011}\%,$ $ \ce{C (gr)} = 20.949\%$, with a remaining $0.04\%$ being mainly $\ce{CH4}$ (methane). The exhaust temperature was 1505.2 kelvin.

Here's my main question; am I right in assuming that $\ce{C (gr)}$ means atomic carbon? Would atomic carbon at a temperature around 1500 degrees kelvin cause any major problems for a rocket engine? I'm assuming that at such high temperatures the carbon wouldn't solidify and cause any serious problems, correct?

Finally; can anyone suggest any other substances that could be used as a dilutent in the aforementioned reaction that would yield a higher specific impulse (anything that isn't liquid hydrogen)?

EDIT: So does anyone have any educated guesses on what would happen to the engine in this case? Thanks for all the responses by the way :)


texts: Most probable point for finding an electron in the 1s orbital of a Hydrogen atom

texts:
My professor says that the most probable point for finding an electron
in a 1s orbital of a hydrogen atom is at its origin.

He explains this by citing the fact that the square of the wave function which gives the probability density is maximum at the origin.

At the same time, we all agree that the Bohr radius is the distance at which probability of finding the electron is maximum for 1s orbital.

I can understand the reasoning he gave about the origin being the highest probable point for finding an electron, but then why are the graphs of the radial distribution function so?


texts: How exactly does electrolysis occur if the molar conductivities of cation and anion are different?

texts:
I'm having trouble wrapping my head around Kohlrausch law of infinite dilution and molar conductivities in general.
For a salt $\ce{AB}$ the molar conductivity at infinite dilution can be expressed as the sum of molar conductivities at infinite dilution of the respective elements.
$$\Lambda^\circ_\mathrm{m}(\ce{AB}) = \Lambda^\circ_\mathrm{m}(\ce{A^+}) + \Lambda^\circ_\mathrm{m}(\ce{B^-})$$
But I don't get how the conductivities of $\ce{A^+}$ and $\ce{B^-}$ can be different.
I thought it means that the ions take different times to reach the electrodes so there should be, let's say, greater movement of $\ce{A^+}$ towards the electrodes so as time passes there should be more negative charge due to $\ce{B^-}$ accumulating in the solution. That's obviously incorrect.
So what exactly does conductivity signify physically if not different rates of migration?


texts: Free automatic organic synthesis Linux command line program

texts: I'm trying to find a free automatic organic synthesis Linux command line program which take mol or smile files as input. I have random molecules and I'd like to know how difficult above a baseline they will be to synthesize. An implementation of synthetic accessibility and not a full step wise synthesis program would also be acceptable. Thanks for the help.


texts: Why does the hexachlorocopper(II) ion not form?

texts:
I am not entirely sure if this question has been answered before, but I was wondering why when copper forms a complex ion with chlorine there are only 4 chlorine ligands. I asked my teacher and he said that it was because chlorine is a weak field ligand. I am not particularly satisfied with this answer as tetrahedral, octahedral and other geometries can be formed by weak field ligands.

So my question is essentialy why is it $\ce{[CuCl4]^{2-}}$ instead of something else like $\ce{[CuCl6]^{4-}}$


texts:
Background: BPA and BPS (Bisphenol A/S) are artificial estrogens and therefore toxic chemicals for us. They are used in the coating of thermal paper. Thermal paper is used to print in-store receipts. There is a growing demand for thermal paper that is free of BPA and BPS for the health and safety of the public.
Question: how do we test it? I heard from someone that both BPS and BPA dissolve in ethanol. If we apply 80% Ethanol solution (commonly found in hand sanitizer) on the coating side of the thermal paper then it reacts (and dissolves) with BPS and BPA; as a result, you notice black and greenish-black spots start to appear on the paper. If the paper is free of BPS/A then no spot or marks will appear on coat-sided paper.
Is this method of testing correct? Does it at least give some accurate idea? What could you suggest for testing?


texts: Understanding what is happening when something is dissovled

texts:
Let's start with a saturated solution of NaCl in water. At this point, any further addition of NaCl at the same T and P would not dissolve. However, if I then add another fully soluble salt (say AgNO3) it will also dissolve until it reaches equilibrium. If I keep adding different soluble salts (assume I don't encounter things like the common ion effect), would I ever overwhelm the solvent such that it could not dissolve anything else?

My intuition is that eventually, there would be no more solvent moleclues available for solvation and thus nothing would dissolve. Is this even valid to think about?


texts: I think that the initial step forms a tertiary amine, which then in the presence of the ketone and trace acid undergoes nucleophilic addition. But then, for the $\ce{HCl/H2O}$ in the last step, which one reacts with the double bond in 1G?


texts:
I have heard a few claims about water-fueled cars. Being a student of Engineering I totally understand that water-fueled cars (using electrolysis to generate Hydrogen) are nothing more than a hoax, unless  you are giving electricity from an outer source.

However, I have heard quite knowledgeable people that water hybrid cars are quite a reality and you can save up to 60% on your fuel costs using some kind of kits. I have difficulty agreeing with this claim as well. I think inclusion of another step (hydrolysis) in the energy cycle of car power system will only make it less efficient. Reason being you can achieve at most as much energy from making a bond (burning Hydrogen) as much you spent on breaking it (Electrolysis).

Can someone please help me understand if I am missing some point? Or I am correct?


texts:
Could you advice an electrode for electrophoretic deposition in methanol which won't spoil methanol and also wont be spoiled by methanol. I googled a bit and found that
1 copper, platinum and gold are catalysts of methanol oxidation
2 aluminum reacts with methanol
3 silicon has poor conductivity...

What can you advice?


texts: Why in positive deviation from Raoult's Law partial vapour pressure of a liquid component is greater than what is predicted by Raoult's Law?

texts:
When my teacher was teaching me positive deviation from Raoult's Law, he told me that in this case
$P_{solution}>P_A^°χ_{A} + P_B^°χ_{B}$
He told that here the solute-solvent interactions are weaker than the solute-solute interactions and solvent-solvent interactions due to which more vapours can be formed from the solution and hence the observed vapour pressure is greater than the theoretical vapour pressure. I was pretty satisfied with the answer and was happy. But after that he told me that in this case, $P_{A} > P_A^°χ_{A}$ and $P_{B} > P_B^°χ_{B}$. He did not give any explanation about it. Okay, the previous explanation makes sense, but how are the above two equations possible? I mean in positive deviation more vapours are formed because solute-solvent interactions are weaker. But there is no change in the interactions between solute-solute and solvent-solvent. So, why are $P_{A} > P_A^°χ_{A}$ and $P_{B} > P_B^°χ_{B}$ true? Shouldn't these equations actually follow Raoult's Law and follow $P_{A} =P_A^°χ_{A}$ and $P_{B} = P_B^°χ_{B}$? Please someone explain as to why $P_{A} > P_A^°χ_{A}$ and $P_{B} > P_B^°χ_{B}$? I am so confused. Please help.


texts: Why is the plateau on a heating curve in equilibrium?

texts:
From the interval of 100 to 140 minutes, why is the substance in equilibrium?

I believe it's because at this interval, freezing and melting begin to occur at the same rate and, when two opposing reactions occur at the same rate, equilibrium is present. However, since the potential energy is decreasing (since the substance is freezing), the equilibrium favors the exothermic reaction causing the substance to eventually become solid in the interval of 140 to 160 minutes.


texts:
Starting from a perfect $\ce{MgO}$ crystal a solid solution of $\ce{Al2O3}$ and $\ce{MgO}$ is prepared with an atomic proportion of $15:85$ of $\ce{Al}:\ce{Mg}$. Knowing the number of vacancies per $\ce{Mg}$ atom is $0.088$, calculate the % variation of density.

My reasoning is as follows:

For every $3~\ce{Mg^{2+}}$ atoms, we have $2~\ce{Al^3+}$ to maintain electric neutrality and 1 vacancy to keep the number of lattice points. Then, in one cell of crystal, which is FCC, there are initially 4 $\ce{Mg^{2+}}$ atoms which will then be redistributed as 2 $\ce{Mg^{2+}}$, $\frac43$ $\ce{Al^{3+}}$ and $\frac23$ vacancies to fulfill stoichiometry.

Then, I calculate the initial density as:
$$\rho_\mathrm o=\frac{(4 \ce{Mg^{2+}}\times\frac{\pu{24.31g}}{N_A \pu{at/mol}})+ (4 \ce{O^{2-}}\times\frac{\pu{16g}}{N_A \pu{at/mol}})}{a^3}$$
And the final density as:
$$\rho_\mathrm f=\frac{(2 \ce{Mg^{2+}}\times\frac{\pu{24.31g}}{N_A \pu{at/mol}})+ (\frac43 \ce{Al^{3+}}\times\frac{\pu{26.98g}}{N_A \pu{at/mol}})+(4 \ce{O^{2-}}\times\frac{\pu{16g}}{N_A \pu{at/mol}})}{a^3}$$

When taking the difference and dividing by the initial density and multiplying by 100%, I get 31.9%, when the solution is 4%. What am I doing wrong?


texts: I have a holding tank on rv, non potable water that I need to heat up to drain . I live in northern Alberta, so the average temperatures are -20. I don't want to wreck anything or gas myself out. I am looking for over the counter chemicals.


texts: Why the term 'unified' in "unified mass unit"?

texts:
Why different unit symbols - amu, u and dalton are used for representing atomic mass? And what does the term 'unified' mean in "unified mass unit"?

Thank you.


texts: DFT calculation of solids with different periods

texts:
I would like to simulate a layer of graphene on a solid substrate, say Cu or quartz. I'm interested in their binding energy and other physical or chemical properties. However, their periods do not match each other, so if I want to use some standard DFT package like VASP or Quantum Expresso, I cannot use a single period for the whole supercell. I had some experience with molecules absorbed on some specific surface, which is an easier case because the period of the supercell is just that of the substrate.

Does anyone have experience with this situation? Thanks.


texts: How the heat a large amount of water that is safe to use?

texts:
I would like to know how heat up a large amount of water ( assumption : 100 liter ) that people could use to take their bath and also it would not be dangerous even if they accidentally ingested it ? .

My idea is that to design a metal container and have the chemical in it . I'll react the chemical that is inside the container and then I'll put the container into the water , which will eventually heat up the water through thermal equilibrium .


texts: Which compound should I avoid in deodorants to avoid "sticky, unwashable" feeling?

texts:
I tried some personal deodorants to avoid the smell of sweat, both in stick, no gas, gas sprays. Some can be washed away easily with body soap on the next day, some require either hair shampoo (because it is significantly harsher than body soap and washes much better) or to wait for two days for the effect to disappear by itself (whether the compounds break down or the compounds get transferred to the shirt is untested).

I don't like to have on me a product I cannot wash away, so I would like to know which compounds in the deo's I should check to avoid the sticky/unwashable effect.

The answer should list or indicate the compounds or rules in a way that people with little knowledge of chemistry can understand, like "the name comprises this string" or something like that. Generic classes which include compounds with a significantly different name is regarded as too complex.

Trying each product may work of course, but then quite some flacons would end up wasted or I would need to use products I don't like for a long time (one flacon lasts months, usually). Also, the composition may change.


texts: Why the bond angle of PH3 is lesser that that of PF3?

texts: We can explain why the bond angle of $\ce{NF3}$ (102°29') is lesser than $\ce{NH3}$ (107°48') by the VSEPR theory, since lone pair lone pair repulsion is greater than lone pair bond pair repulsion. Then for $\ce{PH3}$ and $\ce{PF3}$, also, it is expected that the bond angle of $\ce{PF3}$ will be smaller. But I found that the thing is just reverse. Why is this so? Is it an exception?


texts: Does an atom want to give or take electrons when it has a shell half full?

texts:
For example, carbon has 4 electrons in the outer shell and so its half full. Does it want to give electrons in a bond or take electrons, and if any atom has a half full electron shell does it want to take or give electrons for a covalent bond?
I'm new to chemistry so this question may be simple.


texts: Why is current non-zero when applied potential is still below E$^0$ in cyclic voltammetry?

texts: In this diagram (Evans et al., J. Chem. Edu.) the current is non-zero, but the potential is still below the normal potential. How can the compound become oxidized at the working electrode, when the applied potential is still below the normal potential of the compound?


texts:
Every chemical has a decomposition temperature.  My understanding is that above that temperature molecular bonds are broken.  And if we raise the heat high enough then all molecular bonds will break and we will be left with a "plasma" of ionized atoms, right?

Can the decomposition temperature of bonds be predicted by models, and if so on what data do those models depend?

Now suppose we heat a chemical in an inert (noble) atmosphere, or in a vacuum, to the point of total decomposition.  Now we cool the plasma back to STP.  Are there models that can predict the products we would expect to find – i.e., the right hand side of the reaction equation?

I'm guessing that thermodynamics stipulates we should find the lowest-"energy" compounds that can be created from the constituent elements on the right hand side.

In practice I imagine that achieving that result could require that cooling be done at some "sufficiently low rate."  So, to increase the complexity of the question: Are there any models that can predict what products will be found as the cooling rate is increased?  I believe that in the limit (a virtually instantaneous quench) one ends up with a "glass" (or combination of glass, condensate, and gas) but even then one can't be left with free ions so can we predict the composition of the quenched plasma?


texts: Why London force dominates in Alkyl Halides

texts:
Why London Force is greater than dipole-dipole interactions in Alkyl Halides?

As we know that most of the time London force is weaker than other forces. Then why in this case it's not so?

According to me, due to high charge separation (in C & X) the dipole-dipole interaction must me stronger than the London force which depends more on the surface area of molecules.

Source:Leroy G.Wade Organic chemistry


texts: Any program for conformational searching for sugars?

texts:
I want to estimate mean Gibbs free energy of formation of glucose and for that purpose I think conformers of ring flip should be taken into account. Do you know if some free program can find those structures automatically? (for example Balloon).

The following image shows the conformers I need to get. I am trying to avoid the possibility of drawing it.


texts:
Is the name of this chemical 3-oxopropanoic acid?

I included "oxo"- for the aldehyde group, and "-oic acid" for the carboxylate group.

However, I'm unsure whether this is the correct name since I cannot find it on the internet, while I can find almost all other names I've been trying to figure out.


texts:
I am going to be making a kerosene forge, and I need a refresher on calculus-based chemistry.

Given a certain distribution of alkanes, what is the amount of air (21% O$_2$) needed (in cubic feet per minute [CFM]) at 21C to burn kerosene at a rate of X mL/s?

The distribution of alkanes is unknown but from Wikipedia I've got that the molecules have no more than 16 and no less than 6 carbon atoms. The density is $\mathrm{0.795~g~cm^3}$. If any more info or help is needed, I'll be glad to pitch in where I can.


texts: Identification of dried oil primer vs. acrylic primer on wooden panel

texts:
I am an artist and many years ago I primed a small wooden panel with either oil or acrylic primer. I have since generally noted what type of primer I have used on the backs of canvas stretchers or wooden panels, but for this particular wooden panel I neglected to do so. Is there any relatively easy and inexpensive way to tell if I primed the panel with oil or acrylic primer? There are also a few flecks on the back which I could also use to test. Any odors have since dissipated.
(There are apparently different schools of thought about whether oil can or should be painted on acrylic grounds, but I stick to the practice of painting oil on oil-primed grounds and acrylic on acrylic-primed grounds.)


texts:
Most of the reactions undergo ring expansion whenever favourable.
But this reaction [1, p. 514] doesn't seems to do so:

Practice Problem 11.18 Provide a mechanism for the following reaction.

Could anybody explain why?
References

Solomons, T. W. G.; Fryhle, C. B.; Snyder, S. A. Organic Chemistry, 12e ed.; John Wiley & Sons, Inc: Hoboken, NJ, 2016. ISBN 978-1-118-87576-6.


texts: Adding a base and a salt to a hydrated complex

texts:
The question goes like this:

$\ce{Fe(NO3)3}$ V= $\pu{1 liter}$ and $\ce{[Fe(NO3)3]} =\pu{0.1 moles/liter}$.
Calculate the $\mathrm{pH}$ of this solution using the values of $K$ given.
We add a solid of $\pu{0.2 moles}$ of $\ce{NaOH}$. Give the reactions and the $\mathrm{pH}$. How many precipitation is formed?
After this we add $\pu{0.5 moles}$ of $\ce{KCN}$. Give the reactions, the $\mathrm{pH}$ and the end concentrations in equilibrium.
Given:

$K_\mathrm{st}\,\ce{[Fe(CN)6]^{3-}} = 1\times10^{42}$
$K_\mathrm{a}\, \ce{HCN} = 4\times10^{-10}$
$K_\mathrm{a_1}\,\ce{Fe^{3+}} = 6.3\times10^{-3}$
$K_\mathrm{s}\,\ce{Fe(OH)3} = 1\times10^{-38}$

Up to and including the addition of $\ce{NaOH}$ I understand what is expected and how I should solve for this. However, as soon as the $\ce{KCN}$ is added, I don't know if I should let the $\ce{Fe^3+}$ react first with the $\ce{CN-}$, with the $\ce{OH-}$, or if I should establish a new equilibrium starting from the previous one?
My first thought would be to let the cyanide react completely with the iron-ion, and only form the iron hydroxide with the remaining ions [because $K_\mathrm{st}\,\ce{[Fe(CN)6]^{3-}} >> K_\mathrm{s} \ce{Fe(OH)3}$]. However, in some provided solutions of similar exercises, they seem to let the hydroxide react first with acid, not caring about a higher solubility constant.


texts: Does a live electrical wire change the surrounding atmospheric chemistry?

texts:
Background: I'm world building an Earth-like world for a writing project. One of the goals of this project is to talk about changes in atmospheric chemistry across multiple scales ('nano'-scale through the entire atmospheric air column). My project has a scientist-type character to describe how atmospheric chemistry is affected by different processes. Example: Oxygen is released from leaves during the day, and carbon dioxide is released from leaves at night. Inversion layers occur regularly through the day-night cycle. Altitude impacts the density of air.

Here, I'm curious about the intersection of electricity and atmospheric chemical makeup.

Question: What chemical changes to atmospheric nitrogen and oxygen would/wouldn't occur in the presence of a wire carrying a current (not insulated)? (if any) Put another way, is the chemistry of the air around a live wire different in any way, shape, or form to the chemistry of the air around a wire with no current?

My internet research indicates a few possibilities but I'm not getting a firm sense of the reliability of the results. Example: Maybe ozone is produced by an electrical charge, or maybe it isn't - there seems to be conflicting ideas out there.

Here are some ideas I've seen:

charged particles in the air might naturally gravitate differently towards/away from an electrical current? This would be a change in the movement of existing molecules, perhaps physics rather than chemistry.
dinitrogen and dioxygen might become charged species (will these be positive or negative charges? Is the charge lost easily?
ozone might form?
Other species might form? nitrogen oxide species?

My best estimates for the current are:

~10000 volts and 120 milliamps in one portion of the writing project (electric fence); 120 volts and 20 amps in another portion (electrical cord.) I have some latitude here but those are ballpark estimates.


texts: Enthalpy of mixing of a non-ideal solution

texts:
I have this equation of Flory–Huggins model:
$$\Delta_\mathrm{mix}G = RT(n_1\ln\phi_1 + n_2\ln\phi_2) + \chi n_1\phi_2,$$
where $\phi$ is the volume fraction, $n$ is the amount of substance and $\chi$ is the parameter of solvent-polymer processing that depends only on temperature.
I need an expression for $\Delta_\mathrm{mix}H.$


texts: Should double or triple bonds have preference for low locants in IUPAC nomenclature?

texts: Both double and triple bonds are present in the hydrocarbon shown above, which has the name hexa-1,3-dien-5-yne. Why is the numbering chosen such that the alkene has lower locants than the alkyne? Is there a rule which stipulates that the alkene is a more 'senior' functional group?


texts: Is prefixes such as di-, tri-, etc. considered for alphabetical order in IUPAC nomenclature?

texts:
The correct IUPAC name of a compound was: 4-(1,1-dimethylethyl)-5-ethyloctane.

my question is why not 4-ethyl-5-(1,1-dimethylethyl)octane?

Are prefixes such as di-, tri-, etc. considered for alphabetical order?
and what about prefixes such as cyclo, spiro? Are they too taken into consideration for alphabetical order?


texts: Which gas makes Orange juice bottles swell?

texts:
I forgot a bottle of 1L Orange Juice (100% orange juice with pulp) in the fridge for about a week, the bottle was previously open so air got inside as well.

After a week the bottle got inflated and when I opened it I could hear the gas coming out. No odours, orange juice still the same colour (not sure if the same taste, I threw it away).

Which gas was produced and how did it happen? The air that got in seems to have played a part on it (these bottles stay in the supermarket closed for a long time without getting inflated).


texts:
I know Sorbitol, $\ce{C_6H_14O_6}$ $$\ce {C(OH)H_2 (C(OH)H)_4C(OH)H_2}$$is soluble in water however I did not have much luck finding out whether or not it is soluble in ethanol. My guess is that it isn't however I am not so sure.

Is Sorbitol soluble in ethanol?


texts: What chemical reaction can cause this blue-ish deposit?

texts:
Recently I noticed that some of our glasses and cutlery had developed a blue-ish deposit as you can see for the two sets of spoons below. For each set the spoon on the left has the blue-ish deposit whereas the spoon on the right is the original.

I traced the cause of this blue-ish deposit to a specific effect. It only occurs when the spoon or glass has been used for a medicine called Questran-A, which is a powder that needs to be dissolved in water and then ingested. And more specifically, it only happens when these glasses/spoons are subsequently washed in our dishwasher.

This leads me to believe that some reaction occurs between the (left-overs) of the medicine and the dishwasher tablets. My question is: does anyone know what reaction between the chemicals in the medicine and those in the dishwasher tablets could cause this blue-ish deposit?

Obviously this will be impossible to say without the ingredients of both, so here is a list of the contents of the dishwasher tablets and the medicine:

Dishwasher tablets (Albert Heijn):

pentasodium triphosphate
sodium carbonate and sodium carbonate peroxide
taed
sodium silicate
PEG-90
alcohols, C16-18, ethoxylated mind 30 EO
acrylic copolymer
PEG-4
maleic acid/acrylic acid copolymer,sodium salt
alcohols, C12-18 ethoxylated propoxylated
zinc sulfate
beta-alanine, N-(2-carboxyethyl)-, N-coco alkyl derivs, disodium salt
mn-complex
benzotriazole
subtilisin
tetrasodium etidronate
alpha-amylase
benzisothiazolinone

Questran-A:

4 mg colestyramine
30 mg Aspartame(E 951) equal to 17 mg Phenylalanine
Citric acid(E 330)
kelcoloïd
Silicon dioxide(E551)
Orange flavoring
Xantham gum (E 415).


texts: Comparing acidity of anilinium ion and para-fluoro anilium ion

texts:
Which of these compounds - anilinium ion and para-fluoro anilium ion - is more acidic?

I thought the answer would the be first one since $\ce{-F}$ is an ortho-para activating group, so the electron density at the carbon at which $\ce{-NH3+}$ is attached would be more. I know that $\ce{-F}$ has a strong inductive effect, but since this is para with respect to $\ce{-NH3+}$, I thought I could say +M dominates. However the answer given was the second one. Why is this so and when can I neglect the inductive effect of halogen substituents in benzene to favour the mesomeric effect caused by them?


texts: What type of 2D lattice is depicted in the image shown below? Is it possible to determine without knowing the length of the unit vectors and the angles in between them? I'm confused because it seemingly doesn't fit with either monoclinic or orthorhombic description as $\mathrm{a \ne b}$ and $\mathrm{c\ne d}$


texts: Why does the concentration of hydrogen ions increase in the electrolysis of dilute sulphuric acid?

texts:
In the electrolysis of dilute sulphuric acid, I'm given these two half-equations:

anode: 4OH-(aq) -> 2H2O(l) + O2(g) + 4e-

cathode: 4H+(aq) + 4e- -> 2H2(g)

Why does the concentration of hydrogen ions increase?

Isn't the concentration of hydrogen ions decreasing here, rather than increasing as it is being discharged at the cathode?

N.B: (This question originates from a past AQA GCSE Question: see question 2 part (d) here.)


texts: Removal of calcium from calcium-ammonium nitrate?

texts: I am interested in model rocketry, and need to produce small quantities of pottasium nitrate. For this process I need ammonium nitrate, but I only have calcium ammonium nitrate. Is there a simple process for removing the calcium?


texts: Oxidation state of metal in metal oxo complexes always positive?

texts: Do all metals in metal oxo complexes (eg $\ce{Fe}$ in Ferrate, $\ce{Mo}$ in $\ce{MoO4}$,...) have positive oxidation states?


texts:
Are these 3 molecular structures of ammonium bicarbonate the same?

A:

B:

C:


texts: Why would a ~1 cm thick layer of argon be a significantly poorer conductor of heat than air?

texts:
In yesterday's new Periodic Video, Argon (new) - Periodic Table of Videos, after about 07 min 00 sec, Sir Martyn Poliakoff says:

The final, and I have to admit perhaps slightly boring application of argon, is in double glazing (of windows) to keep our houses warm. Because argon has a heavy atom, the atoms don’t move very fast in the gas phase, and therefore they’re bad at conducting heat (emphasis added).
So if you have double glazing (that’s two sheets of glass in your window) if you put argon between the glass, it is much more effective at insulating the inside of the house, keeping cold out, than if you use air, because air has a much higher conductivity of heat.
So, if you look out of the window, you may find that you are looking through argon gas.

At a given temperature or kinetic energy per molecule, velocity will roughly scale with the inverse square-root of the mass, so I estimate that the argon atoms would be moving
$$\sqrt{\frac{28}{40}} \approx 0.84 $$
only 16% slower than nitrogen molecules would be moving.
Why then would a trapped ~1 cm thick layer of argon gas be a significantly poorer conductor of heat than nitrogen gas or air?
I'm wondering if it has more to do with the fewer internal degrees of freedom of a monatomic gas, than it does with the mass of the molecule. There would be a similar collision rate, but each collision of an atom of Ar could transfer less energy to the glass surface than a molecule of N2 could transfer.


texts: Why does AsF3 boil at 60.4 Celsius and AsF5 at -52.8?

texts: I don't understand why the boiling point of $\ce{AsF3}$ is at 60.4 degrees Celsius and $\ce{AsF5}$ boils at -52.8 degrees Celsius. I understand that it has to do with the bondings, but I can't see what would cause such difference?


texts: Thermodynamics of DNA double helix formation?

texts: The entropy of a system decreases when 2 single stranded DNA molecules come together and form a double stranded molecule. For this to occur the total entropy of the universe must increase. Thus, heat is released when the double stranded molecule forms. My question is: Where does this heat come from?


texts: Percentage of carbon in stainless steel to avoid brittleness

texts: What is the maximum percentage of carbon allowed in stainless steel 202 so that it does not cause brittleness?


texts:
How is Gibbs free energy for a reaction different from that in a process? Is it because a reaction generally occurs at a constant temperature and pressure, and so dG = dH - TdS, while for a process temperature may or may not be fixed for a process, say expansion of a gas, and so dG = dH - TdS - SdT?
Also, how do we define H at non-constant pressure? Is it dH = dU + d(PV)?

Also, why do we say that The G at any point is the max non-mechanical work that can be drawn out? Why does this not include mechanical work too?


texts: Steric effect of t-butyl group on SN1 on a cyclohexane ring

texts:
This is a question from GRB Kota Question Bank Organic Chemistry, Chapter 3, Reasoning type, Q. 4:

Assertion: trans-1-t-butyl-4-chlorocyclohexane is less reactive than cis-1-t-butyl-4-chlorocyclohexane towards an SN1 reaction.
Reason: More the steric factor near the leaving group, the higher the leaving group tendency.

The answer given is:

 Both the assertion and reason is correct and the reason is the correct explanation for the assertion.

The answer given feels wrong.
My reasoning for saying so is because the rate determining step in an SN1 is the formation of a carbocation. Due to this, the steric effect seems irrelevant. However, when the intermediate is same for both compounds undergoing substitution, I assume that the compound having greater stability would be less reactive since the threshold energy required would be greater.
Using the above statement, we can say that trans-1-t-butyl-4-chlorocyclohexane would be less reactive since both the groups are in equatorial position making it more stable whereas in its cis-isomer the t-butyl group would be equatorial whereas the chloride group would be axial.
Due to this, I presume that the assertion is correct. However, the reason seems vague as it does not mention whether the reaction taking place is SN1 or SN2 since this could change with respect to the reaction involved.
Is there anything wrong with my above reasoning? Can the validity of the reason be proved/disproved beyond doubt?


texts: Products of o-aminobenzaldehyde thermal treatment with acetone and further with sulfuric acid

texts:
o-Aminobenzaldehyde is heated along with acetone in dilute $\ce{NaOH}$ solution to produce the major organic product (A), which on treatment with a catalytic amount of $\ce{H2SO4},$ produces another major organic product (B) formed via intramolecular reaction.
What will be the products A and B formed in this reaction?

I have tried solving it and I think A will be o-aminobenzoic acid. But I want to ask that what happens when o-aminobenzoic acid is reacted with catalytic amount of $\ce{H2SO4}?$


texts: I was conducting a titration of a saturated $\ce{Ca(OH)_2}$ solution against $\ce{HCl}$ using a pH meter (the kind with a glass electrode). At the beginning of the titration, the pH reading would drop a bit every time I added a drop of $\ce{HCl}$. However, near the equivalence point, when I added a drop of $\ce{HCl}$, the pH reading would drop rapidly, but then it would rise again at a steady pace for a few minutes. Why does the pH rise again? My teacher said that the pH meter's membrane is somehow becoming "saturated" with the solution, after being left in the solution for awhile. But what's actually going on in terms of the ions and the membrane?


texts: When are transition state's energy barrier "reasonable" at a certain temperature?

texts:
Every computational chemist who does a little bit of mechanistic studies has asked himself this question. When you obtain your first transition state and look at the activation barrier needed to access it, when would you tell that this required energy is reasonable and can be reached at a certain temperature ?

I have heard (never found a proof yet) that a biological process can be performed under standard conditions ($\pu{37 ^\circ C}$) with energy barrier as high as $\pu{15 kcal/mol}$.

Does anyone has a guideline for this?


texts: How to find bond lengths from .cif files of crystal structure

texts: I am confused about how to calculate the bond lengths within a given structure given its .cif file. I have highlighted the bond of interest in the image below. The atom coordinates are shown in the dialog box at the bottom of the screen. I used the formula for calculation of distance between two points in 3-D space (square root of the sum of squares of the differences between corresponding coordinates) and got $\pu{0.2372 \mathring A}$. VESTA gives the bond length as $\pu{1.93 \mathring A}$ angstroms which seems correct given the lattice parameters (cubic, $a=b=c= \pu{8.134 \mathring A}$). Am I missing something here?


texts:
Construct the equation for the reaction between iron(II) ions, hydrogen ions ($\ce{H+}$), and oxygen to form iron(III) ions and water.

The answer is $$\ce{4Fe^{2+}(aq) + 4H+(aq) + O2(aq)->4Fe^{3+}(aq) + 2H2O(l)}$$ Can you explain how to get this answer? Thanks.


texts: Active mass of solids shouldn't necessarily be unity

texts:
I've read that active mass of solids and pure liquids is considered unity. I'm absolutely sure there is some misunderstanding. I know that concentration of solids doesn't change during the course of reaction, but it shouldn't necessarily be unity either. Consider graphite for example. It's density is $2260\pu{g/L}$
$$\text{[C]}=\frac{n_C}{V_C}$$ where $n_C$ is the number of moles of the carbon sample and $V_C$ is the volume of that sample. $$\text{[C]}=\frac{w}{M\times V_C} $$ $$\text{[C]}=\frac{\rho_C}{M}=\frac{2260\pu{g/L}}{12\pu{g/mol}}\\=188.3\pu{mol/L}$$This concentration will be constant throughout a reaction if the phase doesn't change and temperature change is quite small. But this clearly is not unity. Then why is the concerntration of solids considered to be unity?


texts: Schrodinger's Equation and Wave Function

texts:
So I understand that there exists the shrodinger's equation, which on solving,gives the wave function of an electron. The wave function as I understand, gives all possible information about an electron(any extra information on wavefunction will be appreciated).
Could someone actually solve a shrodinger's equation for an electron, and vaguely describe the process involved? Also after the wavefunction is obtained, could you explain to me what exactly does the wavefunction depict, and actually graph it?
I am having a lot of trouble grasping the concept. Any help will be greatly appreciated


texts: What is the meaning of [2,1-c][1,4] in Pyrrolo[2,1-c][1,4]benzodiazepine?

texts:
Pyrrolobenzodiazepines are a group of DNA-alkylating natural products. What is the exact meaning of the [2,1-c][1,4] part in the full descriptive name Pyrrolo[2,1-c][1,4]benzodiazepine?

General structure of pyrrolo[2,1-c][1,4]benzodiazepines. The 2-3 double bond is not present in all natural products.

Thanks to Loong I may be able to figure it out

1,4-Benzodiazepine is pretty trivial, [1,4] defines the position of the nitrogens likeso:

For clarification [1,5] could look like 1H-1,5-Benzodiazepine:

[2,1-c] is answered in What does the "h" "k" and "(5.2.2.02,6)" mean in Dibenzo(h,k)-4-oxatricyclo(5.2.2.02,6)undec-8,10- diene-3, 5-dione

  According to the current version of Nomenclature of Organic Chemistry –
  IUPAC Recommendations and Preferred Names 2013 (Blue Book), isomers of
  fused polycyclic ring systems are distinguished by lettering each
  peripheral side of the parent component using the italic letters a, b,
  c, etc., beginning with a for the side numbered ‘1,2’, b for ‘2,3’,
  etc.

So the letters would be:

So Pyrrolo[2,1-c] would be attached to the c-side.
I still need clarification in one point though:

Does the direction 2,1 (NOT 1,2) show the direction of the attachment?


texts: Keeping Li-Ion battery on charger vs. plug the charger in and out regularly

texts:
I have read on numerous occasions a set of recommendations to keep a Li-Ion battery happy: avoid discharging the device at all costs, don't charge it up completely, keep it as much as possible between 40% and 80% and don't charge it too quickly.

I'm wondering, however, which one of those two workflows are least harmful to a Li-Ion battery:

Keeping the device on (slow) charger most of the time the whole day while using the device, the battery level remaining at 100% most of the time, and dropping sometimes to 80%.
Unplug the (slow) charger regularly during the day, and then plug it again a hour or two later, the battery level constantly fluctuating between 50% and 100%.

I'm asking this question because while it is quite unpractical for me to keep the battery level of my phone between 40% and 80%, it is perfectly possible for me to either keep the phone on charger nearly all the time when I'm at home or at work, or to switch regularly between on battery and on charger modes.


texts:
Q1. If $\pu{1.00L}$ of oxygen gas at $\pu{1.00 bar}$ pressure is combined with $\pu{1.00L}$ of nitrogen gas at $\pu{1.00 bar}$ pressure in a $\pu{2.00L}$ vessel, what is the total pressure in the vessel?

a) $\pu{0.50 bar}$
b) $\pu{1.00 bar}$
c) $\pu{2.00 bar}$
d) $\pu{4.00 bar}$

Q1. If $\pu{1.00L}$ of oxygen gas at $\pu{1.00 bar}$ pressure is combined with $\pu{1.00L}$ of nitrogen gas at $\pu{1.00 bar}$ pressure in a $\pu{1.00L}$ vessel, what is the total pressure in the vessel?

a) $\pu{0.50 bar}$
b) $\pu{1.00 bar}$
c) $\pu{2.00 bar}$
d) $\pu{4.00 bar}$

My thought process:

I know that Boyle's law states that the volume of a fixed quantity of gas at constant temperature is inversely proportional to the pressure, so in these cases it is safe to assume that Boyle's law can be used. For Q1, would the answer be simply 2.00 bars (c)? Instinct tells me it is, but I can't seem to explain why. For Q2, I'd think the answer is 4.00 bar (d) because the volume is halved, so the pressure should be doubled? Again, I'm not too sure though. Any help would be much appreciated.


texts: Why do stabilised ylids lead to trans alkenes in the Wittig reaction?

texts:
Why do stabilised ylids (such as $\ce{Ph3P=CHCO2Me}$) lead to (E)-alkenes in the Wittig reaction, in contrast to unstabilised ylids which are (Z)-selective?

The (E)-alkene is formed from stereospecific collapse of the more stable trans oxaphosphetane. Does the observed preference have anything to do with thermodynamic control over formation of the intermediate oxaphosphetane?


texts: Sign of change in enthalpy and change in entropy

texts:
Why is it wrong to assert that the change in entropy and the change in enthalpy must always have the same sign?
What makes me think that they must have the same sign is the fact that every reaction invariably comes to equilibrium under suitable conditions; and so we have the corresponding temperature equal to $ΔH/ΔS$ (setting $∆G = 0$ in the equation $ΔG = ΔH - TΔS).$


texts: Is there a way to efficiently estimate the enthalpy of formation for an organic molecule in computational chemistry?

texts:
I'm exploring the platonic hydrocarbons and one of the methods I'd like to use is to compare their enthalpies of formation.

The issue is that carbon's standard form is a covalent lattice and I can't think of a way to efficiently obtain its electronic and thermal enthalpies without resorting to optimising a giant PAH.

FWIW I'm using GaussView/Gaussian.


texts: How do I balance the reaction equation of zinc and nitric acid?

texts:
How would you balance the following reaction using the oxidation number method?
$$\ce{Zn + HNO3 -> Zn(NO3)2 + NH4NO3 + H2O}$$

My approach:
Half reactions:
\begin{align}
\ce{Zn &-> Zn(NO3)2} & \text{Change in oxidation state of }\ce{Zn} &= 2\\
\ce{2HNO3 &-> NH4NO3}& \text{Change in oxidation state of }\ce{N} &= 8\\
\end{align}

Multiplying by the L.C.M of the change of the oxidation number.
\begin{align}
\ce{4Zn &-> 4Zn(NO3)2}\\
\ce{2HNO3 &-> NH4NO3}
\end{align}

Adding them,
$$\ce{4Zn + 2HNO3 -> 4Zn(NO3)2 + NH4NO3}$$

I don't know how to proceed further.

Am I going wrong in any of the above steps?
(Please don't convert the reactants and products to ions, and solve it using the method that I am using, so that I can identify my mistake)


texts: How to use the enthalpy of formation to assess the energy stored in a molecule?

texts:
The standard enthalpy of formation for glucose is -2801 kJ/mol, while the standard enthalpy of formation for carbon dioxide is −393.5 kJ/mol.

If one simply examine the numbers attached to the molecules, one may have the impression that far more energy is released from the formation of glucose and thus come to understand glucose as a molecule with a low "level of energy" but this is clearly not the case as glucose is in fact combustible in most circumstance (produce carbon dioxide in the process, spontaneously)

This impression is probably inappropriate as glucose is a far larger molecule than CO2, and thus more changes is done to a greater amount of single-element reactants, but is there a better way to appreciate the amount of energy stored in a kind of molecule based on the enthalpy of combustion?


texts: Why would Auger electron detection have potential for higher spatial resolution than EDX

texts: I understand that Auger electrons are emitted when an electron falls from a higher energy level to a open inner shell and EDX uses electrons that fall from outer shells when an inner shell is kicked off. I also have read that AED has a higher spatial resolution but I don't understand WHY this spatial resolution is higher. What is different about the Auger electrons that increases resolution?


texts: Equilibrium, Kp constant, Partial Pressures

texts:
A system in equilibrium contains
$$I_{2_(g)}\ \text{and} \ I_{(g)}$$
under pressures $$P_1=0,21 \,\text{atm. and}\  P_2=0,23 \,\text{atm.}$$
While its temperature remains constant, we reduce the system's volume to half its original value.

I have to determine $P_1'$ when the system's equilibrium is reestablished.

I know I can calculate $K_p$ and I know I somehow have to use $PV =NRT$, but from there on I am lost, I cannot figure out how to come up with enough equations to find all of my unknowns. Can anyone show me an explicit solution to the problem?

What I tried, but got really nowhere:

$$2I_{(g)} \leftrightarrow I_{2_{(g)}}, K_p=\frac{P_1}{P_2^2}=3,97.$$
$$P_t=P_1 + P_2 = 0,44 \,\text{atm.}$$

When the new equilibrium is established :

$$Kp=\frac{P_1'}{P_2'^2}=3,97$$

$$\frac{2P_1 }{P_1'}=\frac{n_1}{n_1'}$$
and same with $P_2, P_2', n_2, n_2'$, but I don't know where to go from there.


texts: Mathematical basis of why enthalpy of mixing is 0 for ideal gas

texts:
For this case, let's say there are two identical chambers connected by a small tube, constant pressure and temperature. There's a closed valve that separates the two chambers. Within the chambers there are two ideal gases (doesn't matter which, I think; they're ideal gases). I release the valve and the contents of the two chambers mix.

I understand that heat of mixing for ideal gases is 0 conceptually, because the molecules don't have interaction forces between them so introducing the gases to each other doesn't do much with respect to this. But what is the mathematical basis for heat of mixing being 0 for an ideal gas?

quick edit: above might not be clear. I mean that dH=TdS+VdP. In isothermal, isobaric conditions, dP could be zero, but dS isn't necessarily, that'd imply adiabatic conditions. So how is dH=0 for mixing an ideal gas?

Does the above line of thought apply for mixing? If so, do we take the terms before or after the volume increases? (in this case, final volume = 2*initial volume) I feel this is a frame of reference issue, one that comes up a lot for me in thermo.


texts: Why do the NMR peaks shift when H+ concentration and temperature are varied on the reversible hydrolysis of pyruvic acid to 2,2-dihydroxypropionate?

texts:
We performed two experiments. Each of the peaks are referring to the methyl peaks in both reactant and product of the hydrolysis reaction.

We varied $\ce{H+}$ concentration of the reaction and the peaks move ever so slightly right (up field) as acid concentration increases. Why?
As more acid is added there is more pyruvic acid present than the hydrate. But pyruvic acid is more deshielded, so I would have expended it to shift downfield because more deshielded molecules are present.

We varied temperature (45, 50, 55, 60 and 65 °C) and the peaks move slightly left (down field) as temperature is increased. Why?
The only possible explanations I can come up with are that the temperature changes conformations in a way that is more deshielded, but I don't know why specifically?


texts: Why the current of double layer charging is independent of potential?

texts:
i-V curve of double layer charging has a rectangular shape. Why when increasing or decreasing the voltage, the current remains constant?

Or I can ask, how the double layer structure is changing by varying the applied voltage?


texts: Relation between oxoanion acidity and number of oxygen double bonds

texts:
https://en.m.wikipedia.org/wiki/Oxyanion

Was reading the above Wiki page when I came across the 'heuristic for acidity' section which mentions that the oxoanion's acidity can be predicted by the number of oxygen double bonds, with more double bonds making the oxoanion more acidic. My question is, why is this so? Can someone explain it to me by the definition of an acid, and is this prediction basis only limited to oxoanions or can it be extended to other molecules?


texts: Relativistic effects in element 137 (Feinmanium) and above

texts: Here I saw that if an element above atomic no 137 has to exist, it must have electron speed greater than speed of light. My question is , has this calculation  been done keeping in mind Einstein's relativity? {I am just asking, I have not done this calculation.}


texts: What does the peak separation of carbon dioxide IR rotational-vibrational spectrum corresponds to and why?

texts:
Spectrum of $\ce{CO2}$ at $2349\space \mathrm{cm^{-1}}$   region

For some other molecules (for example $\ce{CO}$) the peak separation corresponds to $2B$ (where $B$ is the rotational constant wavenumber)
However for $\ce{CO2}$ when I calculated the peak separation and compared it to literature value, it seems approximately to equal to $4B$? Any idea why is this?

Also, what is the explanation for $\ce{CO2}$ spectrum being asymmetric? and why does the $P$ branch have larger peak separations than the $R$ branch?


texts: What happens if you cool water in a container too small for it to freeze?

texts: Freezing a full bottle of water tends to shatter the glass bottle. What if you used something tougher than glass, like diamond? What would happen if you kept dropping the temperature, but restrained the liquid volume so it couldn't freeze and what sort of force would the liquid exert on the container's walls?


texts: Can the pyrophoric tendencies of a pyrophoric substance be suppressed in a pressurized environment?

texts:
It's common knowledge that the pressure of an environment influences many properties of a substance, like the melting point, boiling point, or triple point. Pyrophoric substances ignite spontaneously at temperatures below $\pu{55^\circ C}$, like caesium for example.

I wish to ask if the tendency for pyrophoric substances to ignite is influenced at all by pressure? Obviously, these substances would not spontaneously ignite in a vacuum, but would their ignition temperature change and/or be dependent on the pressure of their environment? Is there a pressure apart from a vacuum that could cause the substance to lost its pyrophoric properties?


texts: This may seem like a silly question, but is there a flammable liquid that could oxidise itself, so it could effectively burn in a vacuum?


texts: why are lp-lp repulsions greater than bp-lp and bp-bp?

texts: My teacher told me that lone pair and lone pair are closer together hence the repulsion is greater and they take up more space, but I do not understand? can anyone explain it to me?


texts: Is the smallest or largest diameter important for the color of a molecule?

texts:
I learned that phenol absorbs longer wavelengths than benzene because the electron cloud is bigger.

But what is about Penta-1,2,3,4-tetrien (1) and 2,2,-Dimethylpropane (2)?
(1) has the largest diameter but (2) has the smallest. Which one absorbs the longer waves?


texts:
Identify the products $[A]$ to $[D]$:

  $\ce{CH3COONa}+\ce{NaNH2} + \triangle \rightarrow [A]$

  $[A] +\ce{CO_2} \rightarrow [B]$

  $[B] + \ce{H2O} \rightarrow [C]$

  $[C] +\ce{P2O5 } \rightarrow [D]$

  $[A],[B],[C],[D]$ are the main product in each step.

According to my book's answer

$[A]=\ce{NaCH2COONa}$

$[B]=\ce{NaOOC-COONa}$

$[C]= \ce{(CH2COOH)}_2$

$[D]= \ce{C_3O_2}$

I can intuitively understand that product $[A]$ is correct.However I never learnt the next three reactions.Can someone explain/give a source from which I can learn why the next three reactions occur ?

Thanks.


texts: How does a diatomic molecule vibrate in response to heat?

texts:
Do you know of any applet/animation that shows how a diatomic molecule like $\ce{O2}$ or $\ce{N2}$ vibrate in response to/ to produce heat?

Can it vibrate only on one axis, the one joining the two atoms? What happens to the electrons during the vibration?


texts: What is the product of a Dieckmann condensation of dimethyl adipate?

texts: My attempt: $\ce{MeO-}$ preferably gives SN2 or E2, being a strong base and good nucleophile. But which reaction proceeds in this case?


texts: para-dichlorobenzene - number of proton NMR signals

texts: I am told that para-dichlorobenzene exhibits two proton NMR signals. This doesn't jibe with me; all the protons on the molecule are equivalent. Here is a book claiming the same thing. Am I wrong, or is the person who told me that para-dichlorobenzene has two signals on its proton NMR wrong?


texts: How to determine the mole fraction of the liquid phase from a given mole fraction of the vapour phase for a benzene/toluene mixture?

texts:
A quantity of benzene, $\ce{C6H6}$, and toluene, $\ce{C6H5CH3}$, is placed in a $\pu{1 L}$ evacuated vessel at $\pu{25 ^\circ C}$. At equilibrium, a small volume of liquid is visible at the bottom of the container. A sample of the vapour phase is analysed and found to contain $\pu{53 mol-\%}$ benzene.
  What is the mole fraction of benzene in the liquid phase?

  Vapour pressures at $\pu{25 ^\circ C}$: $P_\mathrm{vap}(\text{benzene})= \pu{0.125 atm}$, $P_\mathrm{vap}(\text{toluene}) = \pu{0.037 atm}$

First of all, I am not even certain if this a Raoult's law problem. I just assumed so, since Henry's constant was not given in the problem.

First I'm getting the total liquid pressure using Raoult's law.
\begin{align}
P(\text{benzene}) &= X(\text{benzene}) \cdot P_\mathrm{vap}(\text{benzene}) &
                  &= 0.53 \times 0.125 &&= 0.06625~\mathrm{atm}\\
P(\text{toluene}) &= X(\text{toluene}) \cdot P_\mathrm{vap}(\text{toluene}) &
                  &= 0.47 \times 0.037 &&= 0.01739~\mathrm{atm}\\
P_\mathrm{total}  &&&= 0.06625 + 0.01739 &&= 0.08364~\mathrm{atm}\\
\end{align}

Then using Dalton's law, I am getting the mole fraction of Benzene in the liquid phase.
\begin{align}
P(\text{benzene}) &= Y(\text{benzene}) \cdot P_\mathrm{total}\\
Y(\text{benzene}) &= \frac{P(\text{benzene})}{P_\mathrm{total}}\\
                  &= \frac{0.06625}{0.08364} = 0.792.
\end{align}

However, my answer is incorrect according to the answer key that has $0.25$ as the answer. I have a feeling my whole approach may be wrong since my answer is off by a lot. What am I doing wrong?


texts: What is the 'ancestral term' in the LS coupling scheme?

texts:
On the physics.nist.gov site: http://physics.nist.gov/Pubs/AtSpec/node06.html

The table titled "Atomic structural hierarchy in LS coupling and names for the groups of all transitions between structural entities" contains the hierarchy of atomic LS coupling.  But there is a rather interesting footnote in the table: The letter $\gamma$ represents any additional quantum numbers, such as ancestral terms, necessary to specify a particular term.

What's ancestral term?  Is there an example of this in the literature?


texts:
Which biphenyl is optically active?

I know that it can never be 1. I don't think it will be 4 either as I read that it should be ortho-substituted biphenyl.
So, when I look at 2 and 3, I can't make out which one should be the correct answer.
Should it always be two ortho substituents on each phenyl group for it to be optically active?
Also, what if the two groups on the same phenyl are different, will it always be optically active in that case?


texts: Do different vibrational modes correspond to vibrational energy levels? Or all modes can be found in ground state of the molecule? Or each vibration for each bond has its own vibrational energy levels? I don't understand, please help.


texts: Probability of the single molecule reaction to happen

texts:
I am trying to simulate the single particle second order reactions with known rate constants $k_1$ and $k_{-1}$ in Python. The point of this simulation is to fit the real experimental data to the model and see which theory is working the best.

I have found many different equations for the probability of reactants $\ce{A + B}$ going to $\ce{C}$ and vice versa. The good explanations I found here and here, but the equations are not the same.

So far, I have used those equations:

$$
\begin{align}
\ce{A &->[$k_1$] B} &\quad &p(\ce{A}) = p_a = k_1[\ce{A}]\mathrm{d}t \\
\ce{A + B &->[$k_1$] C} &\quad &p(\ce{A}) = k_1[\ce{A}][\ce{B}]\mathrm{d}t / (V ([\ce{A}_0] + [\ce{B}_0]))\\
\ce{A + A &->[$k_1$] B} &\quad &p(\ce{A}) = 2k_1[\ce{A}]\mathrm{d}t/(2V[\ce{A}_0])([\ce{A}_0] - 1)
\end{align}
$$

I don't expect those equations to be correct, but they work. I would be very grateful for some hints or suggestions!

EDIT: I will post the sample code I was using:

 #A - list with 1 for particle in A or 0 for particle in B, starts with all as 1,
 #e.g:
 A = [1,1,1,1,1,1,1,1]

    for iteration, element in enumerate(A):
        A_conc = len(A[A > 0]) # number of particles in state A

        p(A) = k1 * A_conc * dt      # probability of changing to A->B

        if random.random() > pa:     # checking if random event is favouring transition
            A[n] = 0                 #A reacts to B

This is the way I want to use those equations, but still, the question remains if the equations are correct.


texts:
We need to identify an unknown for a chemistry lab. It's either starch or zinc sulfate.

We know that zinc sulfate is acidic, but what is the pH of starch?


texts: How can we get the toxicity level of a plant without using animals?

texts: We need to know the answer for our research paper. We will appreciate it so much if you will answer our question.


texts: Why does an acid exist when dissolved in water?

texts: Acid is a substance that releases $\ce{H+}$ ions when mixed with water But if it releases $\ce{H+}$ ions the  acid will ultimately not exist. For e.g we take the acid $\ce{H2SO4}$. If we add water then it becomes $$\ce{H2SO4 + H2O -> H+ + SO4^{-2} + H2O}$$ So the bond between hydrogen and sulphate will be broken therefore the acid will not exist, but we see that diluted acids are possible. Why?


texts: Sigma bonds, pi bonds and the puzzling symmetry of methane

texts:
My A-Level Chemistry textbook assures me that:
a sigma bond is formed when two s orbitals overlap.
a pi bond is formed when two p orbitals overlap.
all single bonds between carbon and any other atom are sigma bonds
(side note) double bonds between carbon atoms consist of a sigma bond plus a pi bond
(side-side note) triple bonds between carbon atoms consist of a sigma bond plus 2 pi bonds.
However, the electronic structure of carbon is [He]2s22p2, implying two s orbitals and two p orbitals. I deduce from this that e.g. methane (CH4) has 2 sigma bonds and 2 pi bonds.
I am pretty sure that my deduction is incorrect, as it contradicts the statement in bold above, but cannot see why.
(In addition, the book states that methane has a completely regular tetrahedral structure with all four C – H bonds exactly the same, at identical angles to each other.)
Edit: Although aspects of this question overlap(!) with Can a s orbital overlap with any p orbital to form a sigma bond?, I am most interested in why what appears to a mixture of s- and p- bonds ends up creating such a symmetrical molecule as CH4.


texts:
I have some questions on the nomenclature-
(1) In $H_2O$ we have $H$ written first and $O$ is second but when it comes to Hydroxyl group $OH$ the $O$ comes first, Why?

(2)Why is Propanal called Propion-aldehyde and not Propane- aldehyde?


texts: What really happens atomically in an explosion?

texts: Let's say a room is filled with butane, I then throw a cigarette into the room. What happens to the atoms/molecules of the butane when they are in contact with the heat from the cigarette?


texts: Why value of K(equilibrium constant)becomes squared when we multiply the equation with 2 when its value solely depends on temperature?

texts:
We know that value of equilibrium constant for a particular reaction is independent of concentration of the reactants with which we start or the direction from which equilibrium is approached
But when we multiply the equation (having equilibrium constant K) by 2, the equilibrium constant for the new equation is K^2.
How is this possible? Doesn't doubling of stoichiometric coefficient mean increasing concentration?


texts: Pressure Vs Volume plot for real and ideal gasses

texts:
$$\pmb {\underline {\text {Background}}}$$

Recently I have been studying about the states of matter and came to the topic of ideal gases and real gases and the laws related to them. While studying it from my textbook I saw the plot of pressure Vs volume for real and ideal gas. The problem is that the interpretation that I am getting from the graph is quite contrary to what I have learnt till now (this might be because of some conceptual misunderstanding of mine. Sorry if the question looks foolish.)

$$\pmb {\underline {\text {Question Explained}}}$$

In the above picture  there is a point where real gas behaves the same as ideal gas (where the curves intersect). Now as we decrease the volume in the graph we find that pressure exerted by the real gas is greater than that of ideal gas for a given volume. This seems to be contrary to what I have learnt which is as the volume of a real gas decreases the pressure exerted by a real gas becomes lesser than ideal gas at the same volume (due to increased intermolecular attraction). (In reality even this isn't the case as decreasing the volume much further causes the intermolecular repulsion to overcome the attraction at some point and hence increase the pressure). But as far as I know the graph has been made with the use of the van die Waals equation (I checked it myself via plotting the graph in Demos and it looked the same as shown above). But the assumption with which the equation (and hence the graph) were derived say something different. The equation I'm talking about is $P_{ideal}=P_{real}+\frac {an^2}{V^2}$ and as far as I can comprehend it says pressure by an ideal gas is greater than pressure by a real gas at a given volume. Hence the question

Why does the equation ($P_{ideal}=P_{real}+\frac {an^2}{V^2}$) and graph(shown below) say totally different thing about pressure at a given volume?

Please do point out if I am going wrong anywhere.

Thanks in advance!

Here in thisCrash Course video the same logic as mine is given for decrease in pressure for real gas.


texts: Why does lower concentration cause the metal atoms to dissipate more?

texts:
In a concentration cell, one can measure a voltage because in one of the half cells (the one with lower concentration electrolyte), the atoms tend to dissipate more into the electrolyte as ions, leaving more electrons behind (compared to the other half cell), thus creating a current.
I am not sure if I understand, why a lower concentration causes the atoms to dissipate more. Is it because the atoms of the metal have more contact to water?


texts: Does the word HA always refer to a weak acid?

texts:
I was wondering if HA always represents a weak acid or can it also represent strong acids.
Thank you all in advance


texts: Percentage error. How to find percentage error?

texts:
The Question

  Calculate the percentage dissociation of $\ce{H2S(g)}$ if $0.1\ \mathrm{mol}$ of $\ce{H2S}$ is kept in a $0.5\ \mathrm L$ flask at $1000\ \mathrm K$. The value for $K_c$ for the reaction $\ce{2H2S(g) <=> 2H2(g) + S2(g)}$ is $1\times10^{-7}$.

MY ATTEMPT
Initially there are $0.1\ \mathrm{mol}$ of $\ce{H2S}$ and nothing for $\ce{H2}$ and $\ce{S2}$

Now at equilibrium let us assume $x$ moles dissociated so

$0.1 - x\ \mathrm{mol}$ of $\ce{H2S}$, $x\ \mathrm{mol}$ of $\ce{H2}$, and $x/2\ \mathrm{mol}$ of $\ce{S2}$

Now I know that degree of dissociation = $\alpha$ = amount dissociated/ initial amount in our case $x/0.1=\alpha$ so $x = 0.1\alpha$. So I substitute.

now we have $0.1-0.1\alpha$ of $\ce{H2S}$, $0.1\alpha$ of $\ce{H2}$, and $0.1\alpha/2$ of $\ce{S2}$

Thus
$$K_c = \frac{\left[0.1\alpha/2V\right](\ce{S2})\left[0.1\alpha/V\right]^2(\ce{H2})}{[0.1-0.1\alpha/V]^2(\ce{H2S})}$$
Substituting value of $V$ and solving I reach here

$$\frac{0.1\alpha^3\alpha^3}{( 0.1 - 0.1\alpha)^2}$$

Now my doubt. I assumed $0.1\alpha$ very small in comparison to $0.1$ so I neglected it and assumed the whole $0.1 - 0.1\alpha$ to be $0.1$ only. Now my doubt is that what is the percentage error in my assumption.

On further solving I get percentage of degree of dissociation as $1\,\%$ and that is correct. My method is correct, my only doubt is how to calculate percentage error in my assumption.


texts: I know sulfuric acid is an important catalyzer and is used in various processes. My question is, how do I recover the remaining sulfuric acid? It will be impure, and I don't know how to do the "standard" procedure (is there one?)


texts: A mixture of 4 compounds is extracted with HCl. Which one would go to the aqueous layer?

texts: So this has to do something with the H+ ion bonding with the compound. I dont know how to approach it. The answer given is 2


texts:
So I had a test question the other day, and it essentially went as follows:

  A student measures the concentration of a $\ce{HCl}$ solution to be $10^{-9}$M by using a pH meter. Is the meter wrong?

This means that the $\ce{HCl}$ solution has a pH of 9, which seems unreasonable, yet that is not what I said. I said that the meter is not wrong. My reasoning was that you could have an $\ce{HCl}$ solution so incredibly dilute that the pH would in fact be 9. Since molarity is defined as moles per liter, if you hold the moles constant and increase the volume of solution, you will eventually reach a very tiny molarity.

In essence what I was wondering was: Is my reasoning correct?

Is this solution considered basic?

Can this be generalized such that any originally acidic solution is considered basic at a low enough concentration, or a high enough dilution?


texts: How do the toxicities of arsenate and arsenite compare?

texts: So I was browsing the detoxification metabolistic mechanisms for E. coli, and came across an arsenic detoxification mechanism that converted arsenate to arsenite using a glutaredoxin. So my question is, how does the toxicity of arsenate compare to arsenite? And what is the use of this pathway in E. coli?


texts: Why should the product of the normality of the acid or base and its volume be constant?

texts:
$$\ce{N1V1 = N2V2}$$
 where, N is the Normality of the Acid / Base &
 V is the volume in litres.
We ask you to give a scientific justification or derivation to the above equation
i.e. Why must the product of Normality & Volume be equal for Acid & Base ?

This is a question I found online and would greatly appreciate an answer.


texts: What is the seventh plane of symmetry in benzene?

texts: We get the first six planes of symmetry by joining the opposite edges and vertices. But what is the seventh plane of symmetry?


texts: Why does boiled water have a different taste as compared to cool water?

texts:
I have noticed it frequently and decided to check with some of my peers and friends about this and they too have felt such a thing.
The taste comparison occurs after the boiled water is cooled down to room temperature.
My question is: does water even have a taste?
And whether heating it may change the taste.


texts:
I am currently studying the textbook Infrared and Raman Spectroscopy by Larkin. In the first chapter of the textbook, the author opens (probably prematurely) with the following statement:

  Near-IR spectroscopy measures the broad overtone and combination bands of some of the fundamental vibrations (only the higher frequency modes) and is an excellent technique for rapid, accurate quantitation.

This will likely be covered in later chapters, but the statement piqued my curiosity: For someone who has not yet encountered concepts such as "broad overtone", "combination bands", and "higher frequency modes", what does this all mean? Essentially, I am seeking a brief, but clearer and more elaborate, explanation of what the author has described here.

I would greatly appreciate it if someone who has knowledge of this area would please take the time to clarify.


texts: I completely understand how phenyl group 'releases' or 'donates' electron through resonance, but how is that a phenyl group shows a weak -I effect, despite having electrons literally smeared on itself?


texts: What are the magnetic quantum numbers for the three real p orbitals?

texts:
The form of the p orbitals that we are familiar with are the $\mathrm{p}_x$, $\mathrm{p}_y$, and $\mathrm{p}_z$ orbitals:

(source: ChemTube 3D)

I also know that the p subshells have the quantum number $l = 1$, meaning that the magnetic quantum number can take the three values $m_l = -1, 0, +1$. Which orbital has which value of $m_l$?


texts: Are phenylboranes susceptible to ipso or meta substitution?

texts: Are phenylboranes susceptible to ipso or meta electrophilic aromatic substitution, i.e. what's the regioselectivity?


texts: Can aldol reaction using Evan's auxiliary yield diastereoselective products for ketone substrates?

texts: Evan's diastereoselective aldol reaction commonly uses aldehyde as a substrate and I have never come across an example that uses ketone yet.


texts: Reaction of Alkyl Halide with Ag2S / Na2S

texts: What does alkyl halides give on reaction with $\ce{Ag2S / Na2S}$?  In my book, it is given as $\ce{R-S-R}$ but I am not quite sure as alkyl halide react with moist $\ce{Ag2O}$ to gives $\ce{R-OH}$ and thus I am expecting an analogous product.


texts:
I am working with a sheet of zinc metal where there is an oxide film on it (ZnO) in passivation conditions (pH=10). I have done voltammetry measurements for different scan rates with a 3 electrodes configuration, with zinc sheet as the working electrode. I would like to quantify the capacitive current. How should I process ? How to compensate the iR drop ? What is the crossing point in my curves ?

Thank you ]1


texts: Difference between valency and oxidation state

texts: I know the abstract and sketchy obscure differences but I cannot find anywhere the specific comparison between the concepts of oxidation states and valency including how they are used to describe chemicals.


texts: What were the tests to determine that a substance is an element or not?

texts: What tests were conducted in the ancient days to determine whether a given substance was an element, say, how could one say that mercury, gold, silver, sulphur, phosphorous were elements?


texts:
I found this recipe on how to make a stink bomb:

The recipe basically says to mix ammonia and match heads to create ammonium sulfide. However, I am skeptical, because

It seems that match heads have mostly phosphorus, and only a negligible amount of sulfur.
I can't find any reference for synthesizing ammonium sulfide from ammonia and sulfur; rather, I found that it is synthesized from hydrogen sulfide and ammonia.

Would this recipe still work?

Would it also make malodorants other than ammonium sulfide?

If so, would these other malodorants be safe? Or would it be better to use a different process to create a stink bomb, like using actual sulfur, or something  entirely different?


texts: Comparing retention time of acetic acid, salicylic acid and acetylsalicylic acid in HPLC

texts: I want to compare retention time of acetic acid(AA), salicylic acid(SA) and acetylsalicylic acid(ASA) in HPLC. What are the factors do I have to consider when comparing? Considering dipole moment only, retention time would be AA(1.74D) < SA(2.65D) < ASA(6.49D). Is this correct? (Addition : Mobile phase would be water)


texts: Is there any graph that depicts the deviation of real gases from Charle's law?

texts: I am looking for a graph that shows the basic deviation of a gas from the Charle's law. The graph should be for different values of constant pressures.This would help me evaluate how gases follow ideal behavior for low pressures and high temperatures.


texts: Produce dichlorine oxide by mixing sulphur dioxide and chlorine

texts:
Dichlorine oxide is used as bactericide to purify water. It is produced by the chlorination of sulfur dioxide gas.
  $$\ce{SO2(g) + 2Cl2(g) -> SOCl2(l) + Cl2O(g)}$$
  How many liters of dichlorine oxide ($\ce{Cl2O}$) can be produced by mixing 5.85L of $\ce{SO2}$ and 9.00L of $\ce{Cl2}$? How many liters of the reactant in excess are present after reaction is complete? Assume 100% yield and that all the gases are measured at the same temperature and pressure.

My attempt:

I just finished working out the problem and was hoping to get some feedback on my method of solving.

Convert both reactants from liters to moles using the ideal gas law and identify which is the limiting reactant.

n=$\frac{PV}{RT}$ = $\frac{\pu{5.85L}}{\pu{0.0821m/L}}$ = $71.2m \ce{SO2}$ (Constant T,P)

n=$\frac{PV}{RT}$ = $\frac{\pu{9.00L}}{\pu{0.0821m/L}}$ = 110m $\ce{Cl2}$ (Constant T,P)

$\ce{$71.2$m \ce{SO2 }X}\frac{1m\ce{Cl2O}}{1m\ce{SO2}} = 71.2m \ce{Cl2O}$ Excess Reactant

$110m \ce{Cl2}$ x $\frac{1m \ce{Cl2O}}{2m \ce{Cl2}}$ = $55m \ce{Cl2O}$ Limiting Reactant

Find amount of liters of $\ce{Cl2O}$ that can be made in the reaction by converting limiting reactant from moles to liters using the ideal gas law.

V=$\frac{nRT}{P}$ = $55m \ce{Cl2O}$ X 0.0821m/L = 4.5L $\ce{Cl2O}$ (Constant T,P)

4.5L of $\ce{Cl2O}$ can be produced by mixing 5.85L of $\ce{SO2}$ with 9.00L of $\ce{Cl2}$.

Find liters of excess reactant left over after reaction by finding number of moles of excess reactant that can react with limiting reactant and then subtracting number from original amount of excess.

$110m \ce{Cl2}$ X $\frac{1m \ce{SO2}}{2m \ce{Cl2}}$ = $55m \ce{SO2}$

$71.2m \ce{SO2}$ - $55m \ce{SO2}$ = $16.2m \ce{SO2}$ of excess left over after reaction.


texts:
Why would the following mechanism be valid for the conversion of t-butylbenzene to benzene in highly acidic medium followed by an aqueous workup?

The main problem I have with this mechanism is the formation of the secondary doubly allylic carbocation. Why not go for the tertiary, inductively and doubly allylic stabilized carbocation?

But I guess the problem with going down this path it becomes hard to see how the t-butyl group might leave.

As you can see, the book's mechanism is entirely dependent on having the secondary allylic carbocation.


texts: Mass fraction in a mixture of metal salts given the total mass of the metal

texts:
I am trying to solve a question in my study and I don't get the answer required.

  A mixture of $\ce{NaNO3}$ and $\ce{Na2SO4}$ weight $5.37$ grams, the $\ce{Na}$ = $1.61$ grams. What is the percentage mass of the $\ce{NaNO3}$ in the mixture?

The correct answer according to the book is $45.1\%$, but I get $37\%$.

What is did is:

The weight of the Na is 1.61 total, which means the rest is 3.76 grams
total mass/Molar mass of the rest is 3.76/158 = 0.0238 mol
m(N) = 0.0238*14 = 0.33 grams
m(O3) = 0.0238*48 = 1.09 grams
m(Na) = 1.61/3 = 0.54 grams
total mass = 1.96 grams

1.96/5.37 = 37%

Where and what am I missing or mistaken?


texts: Why energy of some intermediates of glycolysis increases?

texts: It is possible that I do not understand the concept of energy, but according to the diagram in my book, the energy between steps 4 and 5 and between 6 and 8 increases. How is this possible? Also, as ATP is invested in steps 1 and 3, shouldn't the energy increase there?


texts: What chemicals could be used to repair rubber tires?

texts:
I have a beaten old R/C car that I am restoring for my son. It has some nice rubber tires on it, but they are kind of old and worn. The rubber itself is almost moldy and looks matte.

I could just fetch some wonderful product of a shelf somewhere that promises to restore the rubber, but I would like to really know what can be done for old rubber on a low level.

So, how can I treat my rubber, and which chemical process works best (if any)?


texts: What is the crystal structure for a crystal where the ratio of the squares of the angle peaks is 0.825?

texts:
I followed this and it gives an example of how to identify a crystal structure using XRD data.

I have an unknown alkali halide where two peaks were found at $2\theta =25.66$ and $2\theta = 28.3$. I used a copper source for the x-rays. I need to figure out the crystal structure from this. Using the example in the link above, I got

$$\sin ^2 (\theta _1)=0.04931022$$

$$\sin ^2 (\theta _2)=0.05976132$$

Therefore,

$$\frac{\sin ^2 (\theta _1)}{\sin ^2 (\theta _2)} = 0.82511934$$

The PDF only mentions what the result will be for BCC (0.5) and FCC (0.75). Can I reliably conclude that this must be a FCC crystal?


texts: Why is Nitric Acid more reactive and caustic than Sulfuric or Hydrochloric?

texts:
Nitric acid reacts much more vigorously with living tissue and is a obviously more immediately hazardous on contact than sulfuric or hydrochloric.

What is the reason for this?  Is it due to the oxidizing potential of the nitrate anion?

Does the greater reactivity of nitric acid also hold for reactions of acids with metals? Perhaps the factors related to the acid anions that determine dissociation are not the same ones that determine their reactivity?


texts: Removing polyimide coating without damaging carbon nor fused silica optical fiber

texts:
While being manufactured, an optical fiber (fused silica, 125 microns diameter) has been coated with a carbon coating (~50 microns thick) and an external, ~60 microns thick, polyimide coating.

The problem is removing the external coating but not damaging the carbon layer or the glass core. Several procedures are recommended to remove polyimide coatings, being the more usual:

thermal (flame),
chemical (hot sulfuric acid -> within seconds),
mechanical (razor).

After a little research on flame temperatures and other chemical methods (which is a completely unknown field for me), I have found that sodium hydroxide would also attack polyimide while being much easier for me to get than hot sulfuric acid. The questions are: how long could it take to remove the coating along a few cm? Would it damage the carbon layer?

Is there any method I could try?


texts: Conversion of Erythrosine to Fluorescein

texts:
I am a home-chemist and I love dyes. I recently got my hands on sodium salt of erythrosine (tetra-iodinated fluorescein). I want to convert erythrosine to fluorescein. I speculate that using dilute NaOH solution might cause formation of sodium iodide and tetra-hydroxylated fluorescein. How can I reduce the alcohol groups without affecting the carboxylic acid groups.
Is there any better way to convert erythrosine to fluorescein?


texts: Identifying protons in NMR using the J values

texts:
When looking over an old organic midterm I came across this question.

As you can see I got half of it right, but honestly I'm not sure how I got that one right or how you would answer this in general.  Looking back at this now it appears that the first signal was split into a doublet and each peak was then split into a triplet, which makes sense for proton c (first split by b and then by d).

The second one seems trickier.  It looks as though the signal was split into a quartet, and then each peak into a triplet.  To me that looks like it should be d - split into the quartet by e and then split into the triplets by c and b.  So why is the answer b?  These J values wouldn't have been supplied for now reason - is there a way I could have used them?  More generally, is it possible (and if so how) to identify the type of proton and the structure of a molecule if you just had access to the NMR and the J values like this?


texts: Using Distribution Coefficient to Determine Mass and Percent of Acid Extracted

texts:
The $K_\mathrm{D}$ (distribution coefficient) of coffee water at $25\,°\mathrm{C}$ is $7.8$ in a methylene chloride/water system. If there is $2.0\,\mathrm{g}$ of caffeine in $200\,\mathrm{mL}$ of water, calculate the grams and the % of caffeine that can be extracted with a single $100\,\mathrm{mL}$ portion of methylene chloride.

My attempt:

$$\frac{x}{\frac{2\,\mathrm{g}}{200\,\mathrm{mL}}}=7.8$$

$$\frac{x}{0.01\,\mathrm{g\,mL^{-1}}}=7.8$$

$$x=0.078\,\mathrm{g\,mL^{-1}}$$

$$x=0.078\,\mathrm{g\,mL^{-1}}$$

$$0.078\,\mathrm{g\,mL^{-1}}\cdot 100\,\mathrm{mL}=7.8\,\mathrm{g}$$

But I think I'm wrong. Am I supposed to maybe use the molar mass of caffeine ($194\,\mathrm{g\,mol^{-1}}$)?


texts:
I am an electronics guy and not into chemistry so please forgive my ignorance.

A Galvanic Cell is meant to act like a pump, separating positive and negative charges, and thereby creating an EMF. Obviously energy has to be expended in this process.

All my reading tells me that this occurs on account of redox reactions.

If I have understood right, redox reactions happen because of the chemical properties of elements and their atomic structures, and on account of the need for some elements to acquire or get rid of electrons, basically in order to attain octet 'stability'.

Now I presume that this urge for 'stability' is based on the natural process whereby things trend towards their lowest energy states.

Now if this is so, how is it that in redox reactions, charges get forced apart, which requires the expenditure of energy to accomplish. Where, how and why does this energy come from ?

How do we get this free gift of energy from nature just because a chemical element strives towards energy 'stability' by filling an octet.

Obviously I am missing something.

Can someone patiently explain what happens in a redox reaction, and why ?

I request you to use simple examples for electrode and electrolyte materials.


texts: Why is alcohol boiled with HBr for preparing alkyl bromide?

texts:
Alkyl halides are best prepared from alcohols ($\ce{R-OH}$, where $\ce{R}$ is alkyl group), which are easily accessible. The hydroxyl group of an alcohol is replaced by halogen on reaction with concentrated halogen acid ($\ce{HX}$, where $\ce{X}$ is halogen), to get alkyl halides.

Usually we don't need boiling the reactants. But, for the preparation of alkyl bromide requires constant boiling of alcohol with $\ce{HBr}$ ($48\%$). Assume that alcohol is tertiary, so that, we can avoid using catalyst.

What I thought was, alcohol can develop inductive effect, and thus, can get detached with $\ce{OH}$, so that, the bromine from $\ce{HBr}$ can add to $\ce{R}$ group to form alkyl bromide. So, I thought there is no requirement of boiling of reactants, as like we do for preparation of alkyl chloride. Then, why do we need boiling in case of $\ce{HBr}$ and not in case of $\ce{HCl}$?


texts: How to improve efficiency of the diamine synthesis from fluorescein?

texts:
In this work, fluorescein was incorporated with an equal molar of 1-chloro-4-nitrobenzene and double potassium carbonate (molar ratio), the solvent of this reaction is dimethylacetamide (50 ml for 5 g of fluorescein).

The solution was stirred in at 110 °C for 24 h, after that cooled to the room temperature and precipitated in cold water, but a solid, similar to potassium carbonate, remains at the bottom of the reaction vessel, and the efficiency is very low (25%). I don't know the cause of this problem.

This is the structure that I expected for first stage:

In the next step the solid that was obtained from the previous stage, incorporated with 10% Pd/C and methanol. 30 eq hydrazine monohydrate was added dropwise and the solution refluxed at 50 °C for 12 h. After that the solution was filtered to separated catalyst and the crystals of diamine was obtained, but the efficiency of this stage is very low too.


texts: Is the colour of leaves due to d-d transitions in chlorophyll?

texts:
While reading a chapter on transition metals, I came to know that d-Block elements have colour compounds due to d-d transitions.  A question came to my mind as to whether there is any d-d kind of transitions in plants as they also show characteristics colours.

I know the green colours of leaves is due to presence of chlorophyll and also there are coloured pigments in plants.

I may be wrong in my thought, but I really want to clarify my doubt.


texts: Does isotretinoin affects contraception hormonal pills - Ethinylestradiolum, Drospirenonum? Asking as a pharmacologist not a patient.


texts: Are ther known compounds of Argon? What is their molecular geometry and hybridisation?

texts:
Can Argon hybridize orbitals and/or form covalent-like/ionic-like compounds?
Is there any study of that? I would be happy to read concrete references.

What kind of molecular geometries for argon compounds are known or hypothesized at the current time?

Is there some peculiarity to apply something like VSEPR or molecular orbital theory to theoretical or experimentally known argon compounds?


texts: Lowest freezing point room temperature liquid?

texts: What substance that is liquid at STP has the lowest freezing/melting point? I think it's either 2-methylpentane or 3-methylpentane, but I get different numbers from different sources.


texts: SN1 Polar Protic Solvent Stabilization of Substrate

texts:
I know that the standard textbook answer is that a polar protic solvent is able to better stabilize/solvate carbocations through hydrogen bonding.

I understand that a solvent such as water or methanol is capable of hydrogen bonding, but what about the substrate? The substrate is a hydrocarbon; how is the substrate capable of reciprocal hydrogen bonding?

Is this stabilization better described as a dipole-ion interaction rather than a hydrogen bond interaction because I don't see how a hydrocarbon can form reciprocal hydrogen bonding interactions.


texts: Does water have properties suggesting it has a phase transition at 50-63 Celsius so it has two phases?

texts:
https://www.youtube.com/watch?v=YsQXN-Kh2-w&t=497s
In this video, he says that water has four properties (surface tension, refractive index... ) that transition from 50 - 63 Celsius between totally separate values? Eminently testable but I don't have the facilities. I tried searching but there some statements of liquid water having two phases but related to supercooled water. What experimental evidence is there that  water has 2 phases and a transition occurs at 50C?


texts: How to determine the iron content of a screw?

texts:
In Analytical Chemistry, I was asked to determine the iron content of a screw.

I thought it could be solved in the following way:

Treat the screw with a solution of sulfuric acid or hydrochloric acid.
As the iron in solution can be found in the form of $\ce{Fe^{II}}$ or $\ce{Fe^{III}}$, I would reduce the possible $\ce{Fe^{III}}$ ions with $\ce{SnCl2}$ or Walden's reducer.
Titrate the solution with potassium permanganate.
From the volume spent, the amount of iron present could be determined.

I don't know if it will be OK, it is the first time I have faced a problem of this type.


texts: Why is styrene aromatic? Doesn't it have 8 pi electrons, thereby violating Hückel's rule? Can someone offer an alternate, more through explanation?


texts: Greater bond distance for silicon diamond structure than for carbon diamond structure?

texts: In the silicon diamond structure the bond distance is about two times the bond distance of the carbon diamond structure. Is this caused only by the greater dimension of $\mathrm{Si}$ atoms with respect to $\mathrm{C}$ atoms? Or are there other reasons for a greater bond distance in the case of silicon?


texts: How Does The Mordant, Ferric Acetate, Interact With Tannins When Ebonizing Wood?

texts: Ferric Acetate (II) and (III) are "mordants," which intensify wood staining in direct proportion to the tannin concentration in the wood. Some wood stainers add tea to increase the tannin content and thereby make the stain darker. How does Ferric Acetate act as a mordant in this case of ebonizing (web archive) wood?


texts: What are the products of the reaction between fluorine and ammonia? Is it the same as with chlorine and ammonia, which depend upon which reactant is taken in excess?


texts: Dielectric constant and dissolution of ionic salts

texts:
We say that salts like $\ce{NaCl}$ get easily dissolved in water because the dielectric constant of water is very high. I know the dielectric constant of water is 81 and if a salt is put into water the force between $\ce{Na+}$ and $\ce{Cl-}$ ions gets reduced by 1/81 times, after that the salt can easily be dissolved by simply stirring.

But how can we say that the medium between two very small particles which are bonded together is water? How can water molecules be present between two strongly bonded ions?


texts: Why is it that the Lewis structure of $\ce{Cl_2SO}$ has a total of $24$ valence electrons? I thought that the number of valence electrons should be $2\times7 + 1\times6 + 1\times6 = 26$.


texts: Why does cesium have a positive electron affinity?

texts: When an electron is added to cesium, why is energy released?


texts: What compounds are created by mixing Styrofoam and paint thinner?

texts: Yesterday I watched several videos that make a waterproof coat by disolving Styrofoam with paint thinner (my guess is that they use acetone). Will this recipe work for an emergency? Is it toxic (I don't want my pets to fell sick)?


texts: Formation of ferrous chloride or ferric chloride

texts:
Question
When $\ce{HCl}$ reacts with finely powdered iron, it forms ferrous chloride and not ferric chloride. Why?
Answer. Its reaction with iron produces $\ce{H2}$.
$\ce{Fe + 2HCl -> FeCl2 + H2}$
Liberation of hydrogen prevents the formation of ferric chloride.

Now my question is why couldn't it be: $\ce{2Fe + 6HCl -> 2FeCl3 + 3H2}$ ?


texts: Why is pyridine a monodentate ligand, but pyrrole a tridentate ligand?

texts: Is it correct to say pyridine’s non-bonding electron pair does not participate in electron resonance while pyrrole’s non-bond electron participates in electron resonance? Would therefore pyridine’s resonance not be disturbed so act the molecule can act as a monodentate ligand?


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I am aware of the various Slater rules to calculate the effective nuclear charge, $Z_\mathrm{eff}$

However, how can I decide the order in which the orbitals 2s, 3s, 3d, 3p, 4d, and 4f stand when compared regarding the effective nuclear charge on them?

Is calculating the $Z_\mathrm{eff}$ on their individual electrons the efficient way or can some trend or method be established ?


texts: Which of the following can be a source of error in Spectrophotometry? Mark the wrong answer

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a) Differences in solvent
b) Acid base equilibrium (differences of pH)
c) Parasitic or stray radiation
d) Monochromatic radiation
I have some doubts about pH in spectrophotometry. I'm not sure if it is correct but here is what I thought:
a)Differences in solvent. It can be a source of error because disociation, reaction or asociation of the analyte with solvent can generate absorption products different of the analyte.
b)Acid base equilibrium. I don't know why pH is a variable to take into account in spectrophotometry. I thought maybe the case of the determination of phenolphthalein that  depends of pH medium. Spectrophotometry doesn´t work when phenolphtalein is in acidic medium. So pH is a multiplicative interference in this case.
c)Parasitic radiation. It is a source of error because  it is radiation that doesn't come from the analyte and it generates signal.
d)Monochromatic radiation. I think that is the wrong answer because it is what we need to avoid big changes in the absorbance as a function of the wavelength.


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From here

I can see why hapticity changes here, but not why it is necessary for the benzene ring to bend. The resonance energy of benzene is pretty large, and there's no balancing increase in stability elsewhere--unless the decrease of hapticity increases stability, which I doubt (more delocalization=more stability, not vice versa). Also, the concept of a "bent benzene" is a bit strange to me.

I'd like to know what exactly is going on in this reaction and why it happens.

@F'x mentioned that the bent benzene may just be a way of drawing the molecule to clearly show the change of overlap. If this is the case, I'd still like to know how the hapticity changed (because my initial logic behind change of hapticity is invalid if the structure doesn't actually bend).


texts: Are refractive or density based Brix meters better for use with alcoholic drinks?

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Assume that somebody wants to measure the sugar content of a liqueur. It seems that there are two types of Brix meters for it, ones which use the solution density and ones which use refraction of light.

If we have a meter intended for measuring the content of a sugar-in-water solution (and assume that we are talking pure sucrose here, not other sugars), but are using it for measuring a solution which has, beside sugar and water, also 15 to 35 percent alcohol and also unknown organic (colored or transparent) substances dissolved:

which type will give less error, refractional or density-based?
how large will the error be? For example, if the true value is 20 g sugar per 100 ml solution, how far are the values delivered by the meter likely to stray from those 20 grams (I am looking for a back of an envelope estimation, not for an exact interval)?


texts: What is the difference between Molecularity and Order Of Reaction?

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In the field of Chemical Kinetics, terms like Molecularity and Order Of Reaction are often used. I am a bit confused between these two terms.

Can someone explain to me about these two terms and their origins?


texts: In thermodynamics work done by the system is negative but in case of expansion of gas it is positive because force and displacement are in same direction, why?


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$\ce{He2-}$ according to MO theory should be possible with one electron in 2s sigma, but my professor said only at very low temperatures for some reason.

Why only at low temperatures? What is the relationship between the temperature and the stability of that bond? Why is this bond special in this way?


texts: Why don't the products of combustion stop combustion?

texts: We know that combustion of fuels give water and carbon dioxide (during combustion of hydrocarbon) as a byproduct, but why don't these byproducts stop combustion?


texts: Elimination reaction on 2-fluorobutane using alc.KOH

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Question: Find the major product formed when 2-fluorobutane reacts with alcoholic $\ce{KOH}$

My answer: Elimination of $\ce{HF}$ takes place and a more substituted alkene should have formed. (Zaitsev product). I think the mechanism is E2 since strong base is used.

but answer given is a less substituted 1-butene. Is the answer wrong or am I making any mistake?


texts: How do you change atomic valence in Avogadro?

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I have a bridging hydroxyl group between two metals, so the oxygen is triply coordinated in this structure.

How do I change the valency to three in Avogadro so that these bonds to the metal are displayed?

Perhaps it might be necessary to also play around with the van der Waals radius.
Or is there a direct way to enforce a drawn bond between two atoms?


texts: Why is butter harder if it once got warm?

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I realized that butter, when kept cool after buying, can be easily cut and spread when taken out of the fridge. If it gets warm once, however, it will be less soft the next time I take it out of the fridge. If it reaches room temperature once, it cannot even be cut when cooled down again to fridge temperature.

What is causing this phenomenon?

(I refer to real butter from cow milk, not what might be sold as butter in some countries)


texts: Why do pharmaceutical drugs have a expiration date?

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Every now and then you reach into the bathroom cabinet to find that some pill or ointment you where planning to use has gone past its expiration date.

I am interested whether this expiration date has any value. In a short search I found this article from Harvard medical school stating that some test found that 90% of all drugs where still perfectly active 15(!) years after the expiration date. The article then continues to give some vague statements on possible reasons for the expiration date (including financial reasons).

What I am wondering is whether there would be any chemical reasons for drugs to become less effective or even become harmful over time, which could warrant the existence of an expiration date?

As a specific example, in case it is difficult to answer this question in general, let's take an ointment meant to treat muscle pains which use Benzydaminehydrochloride as an active component.


texts: Neighbouring group participation with and without retention of configuration in nucleophilic substitution of 2,6-dichloro-9-thiabicyclo[3.3.1]nonane

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Treatment of the dichloride A under the conditions indicated gives B with retention of configuration, while treatment of dichloride C gives D with inversion of configuration.

I am having difficulty drawing out the inversion ring product to find out if the s lone pair can attack from anti to the $\ce{C-Cl}$ σ* bond on the vertical ring. If it does, then, there is retention of product in the first reaction after the $\ce{N3-}$ attacks.
Can someone please help using diagrams?


texts: What is the meaning of overbased additive in lubricants?

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From the google search that I did, I do not understand what overbased means.

Any comment,link or answer would be useful