texts:
I had to identify the structure of a drug based off the spectra I had. I suck at this. I gave it my best go and got some ugly structure, only to check it using a database and find out I was wrong. I gave up and searched for the chemical structure I was given, only to find out that the drug was diazepam and I was on the right track (my aromatic substitution was correct, and I got the correct degree of hydrogen defeciency, but I didn't know how to tie everything together and I was stuck with one more quaternary carbon that I didn't know where to place). I feel like the spectra I was given are hard to read (specifically the HSQC, HMBC, and COSY); do you all feel the same? I really want to know how to arrive at the answer.
The images are the spectra I was given. I was also given mass and IR strectra, but I cannot post too many pictures with my reputation. If you all need better resolution images, let me know. The molecular formula is C16H13ClN2O, and the groups I found with the IR were NH, C=O, and benzene. I am kind of afraid to ask the instructor at this point because I already found the answer. It wouldn't hurt to ask him anyway, would it? I just don't want to lose points.
EDIT: I took the original images down because I did not want the instructor to find it, if he hadn't already.


texts: How to extract elemental bismuth from pepto bismol?

texts:
I was trying to isolate elemental bismuth from pepto bismol (bismuth subsalicylate) using the process seen here but after I added hydrochloric acid, instead of getting a pink foamy substance, I got a white liquid with some white foam. The only reason I can think of, for why this would happen, is that the pepto bismol was expired by a month.

After I realized the reaction didn't work, I added a homemade universal indicator (red cabbage - phenolphthalein - preserved with a little isopropyl alcohol) and started adding sodium hydroxide to neutralise any remaining acid. When I started adding the sodium hydroxide, the solution started heating up and then changed color fairly rapidly from pink to a dull grey green which didn't change when I tried adding more acid.

Shortly after the color change, something started to precipitate out. I filtered off the precipitate and got a clear orange liquid. I then added a little hydrochloric acid to the orange liquid and something immediately started precipitating out. The remaining liquid then turned clear and smells slightly like mint.

My only guess for what I have made is bismuth hydroxide (the first precipitate) but I have no idea what the second precipitate is. Here are pictures of the final precipitates.


texts: What is the chemistry behind heat produced when blood is bleached?

texts: When I discard blood (20-40 mL) in a beaker containing bleach (400mL), I can feel that heat is produced in the beaker. What is the chemistry behind it? Will heat be produced due to Lysis of haem protein in RBCs? Or any other mechanism?


texts: Acid promoted Enol ring formation Mechanism

texts: I know this has to be an enol mechanism but which carbon gets attacked by the $\pi$ electrons?


texts: Cleavage of 2-Methyltetrahydropyran with HBr

texts: After this cyclic ether is activated with H+, will the bromide attack the more substituted site on the left or the less substituted side on the right? I think it will attack the right because SN2 favors less steric hindrance, but what is confusing me is that for acid activated epoxides, nucleotides attack the more substituted site. Can anyone clarify this for me? Does it have to do with the size of the ring? The charge of the nucleophile? Please help.


texts:
Is it meaningful to characterize the relative strength of desiccants?  For example, is there a measure of hygroscopy, or an ordering of desiccants, such that higher ones will always dry lower ones?

Let us restrict the question to "practical" desiccants, which are hygroscopic substances that can be "recharged" (i.e., dried out) by heating.  I'm not certain I know all possible mechanisms of water sorption within this class of chemicals.  But is it safe to say that for all such chemicals, at standard temperature and pressure, there is some water vapor pressure around a desiccant that has sorbed any water?

I am trying to imagine a series of tests in which two different desiccants are put in a humid chamber in adequate quantities that either could completely sorb all the water.  At hydrous equilibrium will the "stronger" desiccant contain virtually all of the water?  Or is the equilibrium distribution of water a function of the desiccants' relative "hygroscopy," rates of sorption, or some other factor(s)?

This is ultimately a practical question.  One example: I have a hygroscopic, hydrated salt X.  Can I dry it out by sticking it in a sealed box at STP with a "more powerful" desiccant?  If not what determines the limit of dehydration that would be achieved by exposure to other desiccants?


texts: Are there methods for iron content determination in spinach that do not require thiocyanate?

texts:
I am looking for a way to measure the iron content of spinach for a chemistry experiment. Unfortunately I am not sure that thiocyanate will be available and I'm therefore trying to find an alternate method. The most common one seem to be a titration with potassium permanganate. The issue with this method is that other much more abundant metals in spinach would also react with the permanganate.
I had the idea to ash the spinach, dissolve the ashes in water. Then use a displacement reaction since iron is the least reactive metal in the chemical makeup of spinach. I am not sure exactly how but I thought it might be possible to use a compound to precipitate the more reactive ions out of solutions.
Do any of you have some ideas regarding this experiment?


texts:
In the following figure

we can see that the p-orbitals overlap 1s orbital (though relatively very little). How can an electron in p-orbital, be simultaneously in the 1s orbital at any given point in space and time?


texts: Identify structure of compounds from their reactions and molecular formula

texts:
Compound P($\ce{C7H6O}$) on refluxing with aqueous ethanolic $\ce{KCN}$ solution for 1 hour, forms Q($\ce{C14H12O2}$). Q on oxidation gives R($\ce{C14H10O2}$). R on refluxing with aqueous $\ce{NaOH}$ solution followed with acidification forms an $\alpha-$hydroxyacid S ($\ce{C14H12O3}$). What are the structures of the compounds?

My effort:
P has DBE (double bond equivalent) equal to 8, so 2 benzene rings (not possible with 7 carbons) or some cyclic or many double bonds might be necessary. Now some enolate reaction might be happening with $\ce{KCN}$, like  Aldol or Perkin or Knoevnagel or Stobbe or Claisen or Benzion etc. Oxidation doesn't affect the formula so it might be becoming an isomer (that too a functional one). After that a Cannizaro might be the thing.


texts: How can you identify the anode and cathode of a car battery of indistinct shape by using a potassium iodide solution?

texts:
Now I know that the anode in a car battery is lead, the cathode is lead dioxide and the electrolyte is sulfuric acid, but still: how could a potassium iodide solution be used to differentiate between the anode and the cathode?

I mean, lead can't replace potassium in its salt because it lies below it in E.C.S., so how are we supposed to identify them by using potassium iodide?


texts: Why do amides require much harsher conditions for hydrolysis than esters?

texts:
Amides require much harsher conditions to hydrolyse than its ester homologue. An explanation given is that the orbitals holding the lone pair on the nitrogen overlaps with the C=O π-bond to give conjugation, thus introducing a "partial" π-bond between nitrogen and the carbonyl carbon. Consequently, this makes the bond harder to break.
However, for the ester homologue, doesn't this conjugation also happen? An explanation given is poorer overlapping of the orbitals. However, how is that true?
In addition, such explanation is given to show that C=O is shorter in ester than it is in amide. However, I still don't get why this is the case.


texts: Geometry optimization: energy not lowered in every cycle

texts:
I am performing geometry optimizations of an enzyme active site, covalently bonded to a substrate. I have a total of 122 atoms, of which 7 are fixed in space during the optimizations. I am using ORCA to perform D3-B3LYP/6-31+g(d,p) optimizations with the conductor-like polarizable continuum model (epsilon=4).

For certain starting geometries, I notice the energy fluctuates a lot during the geometry cycles, decreasing and increasing. With good geometry convergence I should expect the energy to be lowered in each cycle, but I do not see this. My model should be very flexible, with a lot of shallow energy minima. Could too big step sizes accidentally lead my optimization out of one minimum region and into another, making it difficult to converge the calculation?

Or, more generally, which factors could lead to such a convergence behavior, and are there any common strategies to improve geometry convergence?


texts: How to compare energy levels in hybridized sp orbitals?

texts:
How to compare energy levels in $\ce{sp, sp^2, sp^3}$ orbitals?

Since a higher energy level implies lower stability, an $\ce{sp-sp}$ bond must have the lowest energy level, since it is formed by the overlap of one sigma and two pi bonds in total, more than those in $\ce{sp^2-sp^2}$ or $\ce{sp^3-sp^3}$. Hence, $\text{energy level(}\ce{sp < sp^2 < sp^3}\text{)}$.

Is my calculated trend correct? If so, then is this the intended reasoning? If not, then why?


texts: What are the factors behind making ice faster?

texts:
Recently I saw a video in YouTube about how to make ice in seconds.

In this video, salt is added to a glass of water and then a straw is closed from one end and the other side is lit using a lighter and after which it is stirred for 5 seconds and removed.

As soon as it is removed the ice is formed.

What is the chemical reaction that forms ice so quickly?


texts:
The oncotic pressure or colloidal osmotic pressure is the osmotic pressure developed due to the presence of colloids in a solution. But since the colloids are not true solution, why should the colloids be termed as solutes soluble in the solvent and consequently capable of producing any osmotic pressure? Should they not behave like insoluble substances who do not affect the osmolarity of the solution? And theses colloidal osmotic pressure plays a very important role in trans-capillary transfer dynamics.

If the colloids do affect the osmotic properties, is the expression to measure the colloidal osmotic pressure same as that for true solutions(vant-hoff equation)?


texts: Consequences of ortho effect on resonance

texts:
Consider any carboxylic acid with any group at ortho position. According to ortho effect, the resonance of the $\ce{C=O}$  with the ring is inhibited.

Is this resonance entirely lost? Or some little amount still exists?

Can resonance be present when the participating orbitals are not in the same plane?


texts: How do stoichiometric coefficients effect the half-life of a reaction?

texts:
$$\ce{2A -> 3B + C + 2D}$$

This is a first order reaction. Rate constant $k$ for reaction is given to be (say) $\pu{1.386E-2 min^{-1}}$. From this we get the value of $t_{\frac{1}{2}}$ of reaction as $\frac{\ln(2)}{k} = \pu{50 min}$. Now this $t_{\frac{1}{2}}$ should mean half life time of reaction (and not for $\ce{A}$). However, in my textbook it is written that if concentration of $\ce{A}$ is $\pu{200 M}$ at $t=0$ then at $t = \pu{100 min}$ the conc. of $A$ would be $\pu{50 M}$ as $100$ minutes is two times of the half life (and thus the conc. of $A$ should reduce by $2^2$ times).

I think this is wrong as the half life of $A$ is half of the half-life of reaction (since rate of consumption of $A$ is double the rate of reaction as can be seen from the stoichiometric coefficients). According to me after $100$ minutes the concentration of $A$ should be $\pu{25 M}$. Is my logic correct? Or am I missing something?


texts: What salts (or other substances) are available for increasing water's boiling point?

texts: Increasing the boiling point of water by adding salts or other compounds would be very useful when working with a water bath while refluxing, because with pure water you cannot reach temperatures over 70°C (at that point too much evaporates from the bath). I know that simple table salt would work, but are there other and better compounds/salts available?


texts:
Take the two level system in atomic iodine where the ground state is four fold degenerate and the excited state at $7603 \,\mathrm{cm}^{-1}$ above the ground state (which is taken to have zero energy) and is two fold degenerate from the $^2P_\frac32$ and $^2P_\frac12$ terms arising from the configuration of atomic iodine.

I want to find the temperature at which the ratio of the population of the upper state to the lower state is 1:50.

Using statistical mechanics is it correct to say that this is the case when:

$$
\frac{n_u}{n_l} = \frac{g_{u}\mathrm{exp}(-E_u/k_{\mathrm{B}}T)}{g_{l}\mathrm{exp}(-E_l/k_{\mathrm{B}}T)} = \frac{2\mathrm{exp}(-7603.hc/k_{\mathrm{B}}T)}{4} = \frac{1}{50}
$$

Rearranging for T and substituting in the values of the constants gives me $3401.9 \,\mathrm{K}$ which seems alarmingly high. Where have I gone wrong?


texts: What is the major product of the nitration of N,N-dimethylaniline?

texts:
What is the major product when N,N-dimethylaniline, $\ce{C6H5N(CH3)2}$, reacts with concentrated nitric acid (conc. $\ce{HNO3}$) in presence of concentrated sulphuric acid (conc. $\ce{H2SO4}$)?

Here, nitrogen  gets protonated. So, it becomes deactivating, but it can't be stabilised by resonance because it would exceed valency of nitrogen. So, is meta or para the major product?


texts: Is $\ce{Al(OH)3}$ in a very dilute solution deemed as a strong base? Are there any actual experimental data for it?


texts: Why is polymer B more dense than polymer A?

texts:
The official solution is that A has branched / side chains, weak Van der Waals forces between the polymer chains, less compact packing than B, and large inter-chain distances.
B has no branched chains, hydrogen bonds between the polymer chains, compact packing, and small inter-chain distances.

What does a branched chain mean? How does this influence the density? Doesn't B also have side chains?

What does 'compact packing' mean in this case? Does it mean that separate chains are packed closely together, or that in a single chain, the molecules are closer together?


texts: what causes the smell of a room ionizer? If ozone, what are we actually smelling when ozone interacts with nasal mucous?

texts: This touches on how smell works, but my intent is ask about the mechanism for why do ionised smell like they do?  I would like to get one step past ozone if that is the primary mechanism.


texts: While finding the solution to the question that which among BaO and BaCl2 has hi that is energy I found that it was BaO whose lattice energy is high and there were explaining it just with charges. So I am bit confused that why did they not consider the the fact that there were 2 Cl atoms in BaCl2


texts: How Does One Create A Cellulose Ingredient For Use In The Creation Of Glucose?

texts: I am attempting to begin synthesizing glucose, however I will require a form of ball milled cellulose as a main ingredient. Having been said, what methods would be recommended to create the Cellulose? If we were to use grass clippings or cotton as our source for example, what steps would we take in order to gain the desired material from the aforementioned source?


texts: Equilibrium Concentrations of Products/Reactants

texts: Does increasing the concentration of reactants mean the equilibrium concentration of the products will be greater (than the concentration of the reactants?)


texts: Colour change of fluorescein in acidic and basic medium

texts:
I prepared fluorescein for my chemistry project in school and I realised that this molecule and its preparation steps are very closely related to that of phenolphthalein. I have studied briefly about the colour change in phenolphthalein in different mediums.

What I have thought is that the colour change is due to increase or decrease in density of quantised states due to increase or decrease in pi conjugation (Not sure about that though). I tried to observe colour change of fluorescein in strongly acidic and basic medium.

What I noticed was that in acidic medium, addition of small amount of fluorescein gave red solution whereas when the same amount was added in basic medium, it gave fluorescent green solution.

One form of fluorescein is shown below (1); in basic media it cyclises to form a lactone (2):

But I couldn't figure out how this relates to the colour. I thought that the acidic form 1 would have greater π-conjugation, the energy gap between the electronic states would be smaller, and light of a lower frequency (longer wavelength) would be absorbed.

However, the opposite is observed. What is actually going on?


texts: Quantum Mechanical Model of An Atom, Shells, Subshells

texts:
I've just been introduced to the quantum Mechanical Model of an Atom, so please bear with me on this one.
Are Subshells and shell physical things, like do they really exist, or is it a concept only to understand the energy that an electron has?
I'm kind of confused since until now, we've been drawing the K, L , M , N shells with a nucleus in the middle and 4 shells outside with the respective no. Of electrons in them.
And they're related to distance from the nucleus so I was thinking they must be physical.
But if you start visualising each Subshells in each shell having it's own orbitals, that doesn't really make sense.
And what about orbitals? I'm guessing they've  got to be physical, right?
- 10th grader
edit- My point is can you literally visualise the different things as it's regularly down at middle school level.


texts:
I know that NBS is a selective brominating agent especially on the allylic position. And its reaction mechanism is of free radical.

But I can't figure out the reason for the change in position of the double bond in the products.

It would be helpful if someone could give the mechanism along with its reason.

This is what I'm thinking, that might be happening there but still I don't understand how and why something like this would happen.

My mistake, number 3 and the product which I have marked as not formed are same.

2)Which one among these three products is the major product?


texts: Why do amides have an inconsistent boiling point trend?

texts:
For many organic compounds such as alcohols and alkanes, the relationship between molar mass and boiling point is generally linear when graphed. However, amides have a very high boiling point and as molar mas increases, the increase in boiling point is not directly proportional and sometimes even decreases (although it remains very high). Whats the exact reason for this?
Sorry if this is a duplicate question.


texts:
This is benzene-1,4-diol. Its common name is quinol and hydroquinone. How is hydroquinone an accepted name since the functional group here is an alcohol and not a ketone? Is this the only such case or does it apply elsewhere too?

This is benzene-1,2,4-triol also known as hydroxyquinol. How does the position of alcohol influence the name of the compound here?


texts: Why do acids favor the oxidizer? And bases the reducer?

texts: Simply put, why does adding acid to the cathode up the cell voltage? From what I understand, acids are proton donors. Do these positive protons attract electrons toward the cathode compartment of the electrochemical cell?


texts: Why does selenophene not undergo aromatic substitution?

texts: Other derivatives like thiophene, pyrrole give electrophilic substitution but why not selenophene? Is it because selenophene does not have enough electron donating effect and not having its electrons in conjugation, making the ring anti-aromatic?


texts: What is the difference between polyethene and polyethane?

texts: The monomer in polyethene seems to drop the $\ce{C=C}$ bond and end up with a $\ce{C-C}$ bond. The polymer chain then looks like $\ce{[CH2-CH2]_{n}}$. If I were to look at that polymer chain I would probably call it polyethane not polythene (or I could even call it polymethane) because it doesn't have a double bond, so I wouldn't classify it as an alkene. Am I doing something wrong with my analysis here? Or is there some sort of rule about nomenclature that change when things become polymers and drop a functional bond (in this case the $\ce{C=C}$ bond)?


texts: Predicting bond-strength of metal carbonyls

texts:
The metal carbonyls (and similar organometallic compounds) involve a combination of sigma bond, a pi bond and backbonding. The bond strengths under consideration are the metal-carbon bond and the carbon oxygen bond. Here is the original question:-

  Predict the order of $\ce{C-O}$ bond strength in the following:-
  I) $[\ce{Mn(CO)_6}]^+$
  II) $[\ce{Cr(CO)_6}]$
  III) $[\ce{V(CO)_6}]^-$

All of these are isoelectronic, and hence whatever the difference of bond strengths, must arise from the difference in the resultant nuclear force of attraction. Since $\ce{Mn+}$ has the highest charge density, I would assume that the $\ce{M-C}$ bond strength of the manganese compound is the strongest (vanadium being the weakest) and therefore, the $\ce{C-O}$ bond strength must follow the opposite order, as the strengthening of the metal carbonyl bond should weaken the carbon oxygen bond.

But the answer given is III<II<I, exactly the opposite of my prediction. Why is it so? A relevant factor which I didn't consider is the back bonding, but I am unsure of how to integrate that into my prediction. Also, how would we make a prediction if the given compounds were not isoelectronic?


texts: What happens in the reaction of ammonium dichromate and mercury(II) thiocyanate?

texts:
I found this reaction of $\ce{NH4Cr2O7 + Hg(SCN)2 ->[\Delta]\ ?}$ on youtube, and I'm curious as to how it works. I tried searching online, but didn't find much on it.

Thanks.


texts: Is my reasoning for resonance structures correct?

texts:
given this picture, which resonance structure is correct? I'm thinking 1 and 3. You can't have 2 because the carbon which originally had a negative charge would be making 5 bonds, and you can't have 4 because the carbon on the right side of the new double bond would also have 5 bonds.

So is this reasoning correct? I'm just having a bunch of trouble drawing resonance structures.


texts: Unknown Mass in Dalton's Law of Partial Pressures

texts:
An air with mass of $0.454\ \mathrm{kg}$ and an unknown mass of $\ce{CO2}$ occupy an 85 liters tank at $2068.44\ \mathrm{kPa}$. If the partial pressure of the $\ce{CO2}$ is $344.74\ \mathrm{kPa}$, determine its mass.

Answer is $0.138\ \mathrm{kg}$

Ok lets setup Dalton's Law:

$$\begin{align}
p_\text{total} &= p_\text{air} + p_{\ce{CO2}} \\
2068.44 &= \left(mRT/V\right)_\text{air} + 344.74 \\
m_\text{air} &= 0.454\ \mathrm{kg} \\
R_\text{air} &= 0.287\ \mathrm{kJ/(kg\ K)} \\
T_\text{air}/V_\text{air} &= 18847.73126
\end{align}$$

Ok so I need to get something out of:

$$\begin{align}
T_\text{air}/V_\text{air} &= 18847.73126 \\
V_\text{total} &= V_\text{air} + V_{\ce{CO2}} = 0.085\ \mathrm{m^3}
\end{align}$$

Ok so im basically stuck there. only 2 equations for 3 unknowns.

Any hint? or am I totally approaching this the wrong way?


texts:
Why must 3 equivalents of sodium amide be used here to form the alkyne? The part I specifically have issue with is in red.

From what I understand, we should just use 2 equivalents of sodium amide to get rid of the bromines and to form the alkyne. Another equivalent of sodium amide will form the acetylide anion. Removing two protons effectively forms the triple bond and eliminates the two halogens. Also, take a look at example 3 here ..

Why then does the book's solution manual want me to use 3 equivalents of sodium amide to get neutral acetylene, and another equivalent to get to the acetylide ion?

As you can see, my book's solution manual contradicts another book's discussion of obtaining alkynes from vicinal dihalides.


texts: Determine vmax and enzyme concentration (Michaelis–Menten)

texts:
I am given that the enzyme concentration is $\pu{15 nM}$ and the following data:
$$
\begin{array}{rl}
\hline
S/\pu{mM} & V/\pu{mM s^{-1}} \\
\hline
1 & 0.202 \\
2 & 0.368 \\
5 & 0.729 \\
10 & 1.08 \\
20 & 1.43 \\
50 & 1.77 \\
100 & 1.92 \\
\hline
\end{array}
$$
And calculated that the Michaelis–Menten constant was $K_\mathrm{M} = 9.41$ (unsure about the units).
I then want to calculate $v_\mathrm{max}$ and $[\ce{E}]_0$ for the same reaction given that the reaction rate is $\pu{0.101 mM s-1}$ at a substrate concentration of $\pu{24 mM}.$
I know that once I have $v_\mathrm{max}$ I could just use $v_\mathrm{max} = k_\mathrm{b}[\ce{E}]_0$ to calculate the enzyme concentration, but I am unsure as to how I can calculate $v_\mathrm{max}$ from one set of data. Could someone give me a hint of how to begin this problem?


texts: Why is H bonded to C5 drawn below the plane in Haworth formula for D-glucose?

texts: I have always seen the hydrogen atom bonded to C5 drawn below the plane as in the following figure. Shouldn't it be drawn above the plane since it is drawn on left side in Fischer projection?


texts: Color imparted to flame and color of coordination compounds

texts:
When we heat a ionic substance/compound, the ionic bond gets weakened and the metal is ionized. Is the color imparted to the flame due to absorption of light? i.e. Do we see the remaining wavelengths? Or is it due to the falling back of electrons to their ground state?

Shouldn't we be seeing two colours one after other? Since the electrons take up energy of particular wavelengths (so we see the remaining colours) and then the wavelength which got used up earlier returning back when electrons return back to the ground state?

The coordination compounds should also show same dual-color property. Since when electrons absorb energy they go from t2g to eg and when they return, they should give back the wavelength.

This could also be said for halogens.

Why do we see only one colour? Which colour is it in which case? The absorption one or the emission one?


texts: Does mercury chloride (ii) evaporate at room temperature?

texts: if you leave mercury chloride (ii) exposed to air in a room does it evaporate to any significant level which can cause toxicity?


texts: Bromination of 1,3,5-cyclooctatriene followed by nucleophilic substitution by excess dimethylamine

texts:
Write the mechanism for the following reaction (bromination of 1,3,5-cyclooctatriene followed by nucleophilic substitution by excess dimethylamine):

My answer so far:

I have only shown one of the reactions, I presume it is the same for adding the other $\ce{Me2NH}$ on the other side.
How do I get rid of the second bromine, or does just one of the Br's add? If it is only one, why, because you usually use $\ce{HBr}$ for that?


texts:
What is the relationship between electric potential and conductivity?

For example, gold has a more negative electric potential than silver (-1.100 vs -0.800), but silver is a better conductor.


texts: Why can't there be more hydrogen ion concentration in acids or lesser hydrogen ion concentration in bases? Why should there even be any hydrogen ion concentration in alkalis? (I know pH is calculated by the negative log of H+ ion concentration.)


texts:
I found this problem:

  The oxide of a metal contains 60.0% metal and the chloride of the same metal contains 25.26% metal (in mass percents). What are the possible formulas for the oxide and the chloride?

I looked up the solution and it states that the results are $\ce{MgO}$, $\ce{MgCl2}$, $\ce{TiO2}$ and $\ce{TiCl4}$, but I don't understand how they got it. How should I approach this kind of problem?


texts: Limits on contaminant size in filtration for extraction, and standard alternatives?

texts:
Following up on How to perform solvent extraction of a solid I realized that I haven't quantified the size of the contaminants.  I know they aren't soluble in acetone and the target is, but I don't know how small the contaminants are.

Once the target is dissolved presumably I must assume that suspended contaminants are as small as their molecular size.  In this case is a filter-based extraction still possible?  I don't see lab filters like extraction thimbles sold by filtration size.

In a case like this is the correct approach to run the solution through a centrifuge and then suck out the middle solution with a pipette?  (Or what is the lab best practice for mechanical extraction following spinning?)


texts:
In a particular question in one of my reference book, I was asked if the given compound (meso-butane-2,3-diol) was a meso compound or not.  In it’s solution part, to show that the compound was actually meso, they did the following.

As I was not convinced about rotation of C2, I searched the web where I found this which says

  While rotating the bonds about any atom
  (chiral) the stereochemistry of the molecule
  does not changes.

This is what I am confused. I mean if we rotate meso-butane-2,3-diol in the given way such that we have a conformer other than eclipsed or staggered, wouldn’t it be optically active, without any plane or centre of symmetry, which means rotation does change stereochemistry. Where am I going wrong?


texts: Book reference for electronic occupation of TM

texts:
Is there a book I can reference that has a table like this? I can't reference an online source on my thesis and all the pictures I have found online like this don't make their reference explicit.

Thanks!


texts: What does the term 'by mass' mean with respect to different contexts?

texts:
I've seen the term 'by mass' being used in various sorts of contexts. Some, while explaining the law of definite proportions say, the 'same proportions by mass', some say 'constant chemical composition by mass'.
What does the term 'by mass' mean? Does it mean in a proportion/ratio, we have mass as both, the denominator and numerator?
When I say 'percentage by mass', what would that mean?


texts: Qualitative Analysis- Distinguishing between two ions or two salts

texts:
I know my question is going to be quite below the level of this site but I am 1st grade in university and I can't understand anything.

I am going to give an example from the book: distinguish between $\ce{AgI}$ and $\ce{AgCl}$. Answersheet tells me to add $\ce{NH3}$; only $\ce{AgCl}$ dissolves. I don't even know why $\ce{AgI}$  precipitate and $\ce{AgCl}$ dissolves.

Or there is another question: distinguish between $\ce{Ag+}$ and $\ce{[Ag(NH3)2]+}$. And answer sheet tells to add NaCl and only $\ce{Ag+}$ gives a precipitate. Why doesn't $\ce{[Ag(NH3)2]+}$ also give a ppt.?

How do I know which cations or anions or salts are soluble in which solvent? What should I look when I am trying to distinguish ions or salts? Or how do I know if there is no reaction? I know these questions are too general but I am having a hard time understanding this class.

You can either answer the questions from the book (which I failed to understand) or help me to understand the basis of the subject by answering others. Or both. I would really appreciate any kind of answers coming from you.


texts:
In the synthesis of (S)-Diphenyl(pyrrolidine-2yl)methanol, I need to extract the product using an organic solvent and water. Which organic solvent is the most suitable in this case?

Ethyl acetate: I think that it is miscible with water and it can form an emulsion, for this reason I would not choose it.
Hexane: it is an apolar solvent so maybe the product is not very soluble in it.
Ethanol: I think I cannot use it because it is miscible with water.
Diethylether: it is an apolar solvent so maybe the product is not very soluble in it.
Dichloromethane: I think that this is the best choice because it is not miscible with water and the product should be soluble in it.

Is my reasoning correct?


texts: Why is Vapor Pressure of Liquid Equal to Ambient Pressure at Boiling?

texts: What does phase change from liquid to gas have to do with equality of vapor pressure and ambient pressure? I understand that at higher pressures more kinetic energy is needed for molecules in liquid to spread out to form bubbles of vapor since vapor has lower density than liquid which means that higher temperature is needed. But why should equality of vapor pressure and ambient pressure determine when phase change takes place?


texts: Possible Products in the Addition To a Double Bond in a Ring

texts:
I don't understand why both these products should be different. I know hydrogenation is syn addition and both the hydrogens add from the same side, but why should the plane in which both the hydrogen atoms are present even matter?

Also, bond rotation is possible around sigma bond which makes both these products identical.

Please explain why the two products are different and where am I wrong with this logic?


texts: Is activated carbon classified as organic or inorganic?

texts:
Organic compounds are typically defined as “molecules containing carbon”. Wikipedia states that there for some historical (read: non-logical) reasons,

  a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the allotropes of carbon such as diamond and graphite, are considered inorganic.

I thus wonder: is activated charcoal (also known as activated carbon) typically classified as an organic or inorganic material?

If I follow the list of exceptions given by Wikipedia, it should be organic (it's not an allotrope of carbon, in particular), but I get the feeling that most people in the field of porous materials would classify it as inorganic. So, I'm looking for an authoritative reference on this question.


texts:
Somebody I know insists that the use of a catalyst increases the atom economy. They did chemistry at school and were told that a catalyst increases the atom economy. He pointed me to several past exams where this was written as a valid answer.

However, I am convinced that this is false. After all, atom economy is:

$$\text{atom economy} = \frac{\text{molecular mass of desired product}}{\text{molecular mass of all reactants}} \times 100\%$$

I feel this has nothing to do with a catalyst.

Am I missing something?


texts: Mechanism of manganese dioxide induced decomposition of hydrogen peroxide

texts: What is the mechanism involved in the decomposition of hydrogen peroxide with manganese dioxide as the catalyst?


texts: How much does water expand when heated, and does salt affect that?

texts:
For this question, assume all things not mentioned are perfectly controlled, all at 14.7lbs of atmospheric pressure, and water is 100% pure of anything not mentioned, with no dissolved air.

Given a quantity of water that is 1 liter at 20°, what would the volume be when heated to 30°?

Secondly, the same question, except the water being heated is fully saturated with salt.


texts: What all information can be gathered qualitatively from the radial distribution functions of a molecule?

texts:
Apart from knowing the radius of coordination shells and the probability of finding, is there any other thermodynamic  information we can gather by looking at radial distribution functions of a molecule?

For instance, If I plot the radial distribution functions for 'O' atom of H2O, once for pure H2O and then once in the presence of ethanol. Will i be able to relate the excess molar volume through the radial distribution functions?
What other information can I get?


texts:
Upon scouring Wikipedia for info about fullerenes to research, I came across this paragraph in the page on Buckminsterfullerene (C60):

  Under high pressure and temperature, repeated [2+2] cycloaddition between
    C60 results in a polymerized fullerene chains and networks. These polymers
    remain stable at ambient pressure and temperature once formed, and have
    remarkably interesting electronic and magnetic properties, such as being
    ferromagnetic above room
    temperature.[43]

This sounded like a very intriguing topic, and I instantly got hooked. However, the source that it cited was "Chapter 14: The group 14 elements" from some inorganic chemistry textbook, and contained little more information than the quote above. Upon performing an internet search, I found little related research, and no online journal that both published the research and was one that I had access to. If anyone has more information about this mysterious polymer or it's variations, properties, or related research, I would be grateful.

Note that I'm not referring to the dumbbell-shaped dimer of C60, which I found plenty of research on. However, all answers and contributions about the polymeric form are greatly appreciated.


texts: How dangerous are these soil organic carbon digestion methods?

texts:
I have several ground up soil samples that I need to get fractions from. The fractions are based on the Century Soil Model. Briefly, the fractions relate to the approximate time frame it takes for an organic carbon pool to be metabolized in the soil. Fast pools ≈1 year, slow pools ≈10+ years, etc.

I have looked at several papers to try to get an idea of the chemical methods used for digesting the soil samples to get at the more stable carbon pools. For more easily digested organic carbon pools, hot water seems to work, but for the middling and more recalcitrant pools, other reagents are used.

Some methods mentioned include:

dissolve in $\pu{0.1 M}~\ce{NaOH} + \pu{0.1 M} ~\ce{Na4P2O7}$
dissolve in $\ce{HCl}$
reflux with $\pu{6 M} ~\ce{HCl}$
"stepwise chemical digestion with cold and hot $\ce{H2SO4}$
(95 - 98% concentration)"
oxidation with $\ce{KMnO4}$ ($33\text{ or }\pu{333 mM}$)  (this one I see mentioned most frequently)

I am not a chemist. I took the required chemistry classes for my degree and passed, but that's years ago now. When I did do chemistry labs, my results hardly ever came out as they were supposed to, so my skill in this field is minimal. Besides these methods not working, and thus wasting time and money, my real concern is how potentially dangerous these chemicals are. Would someone be so kind as to give me an indication of how risky these chemicals might be? We have a functioning fume hood, will buy PPE, and be sure there are safety procedures in place, but I'm still wondering how much I should worry if a flask breaks or something spills.


texts:
I am trying to solve a question that asks to compare Q vs. K. K = 4.2, and Q = 1.0.
Problem Details:

2.0 mol of Samples of A, B, and C
$\ce{A + B \rightleftharpoons 2C}$

I know that the reaction equilibrium is to the right, but, from this information, how can I tell if it is far to the right or slightly to the right?
Thanks.


texts:
"In the titration of a solid acid, an endpoint is reached after 22.0mL
  of 0.120 M $\ce{NaOH}$ has been added. Assuming that each acid particle
  contains two acidic hydrogens and both are neutralized, what is the
  molar mass of the unknown acid?"

I really don't know how to solve this. I've figured out how to calculate the moles of acid were in the sample but don't see how to find the molar mass from that...any ideas?


texts: How to determine the pH range at which maximum hydrate is present?

texts:
Question:

Find the $\mathrm{pH}$ range at which maximum hydrate is present in a solution of oxaloacetic acid (given $\mathrm{pK_a}$ of $\ce{-COOH}$ in the left is $=2.2$ and on the right is $=3.98$):

I understand that the hydrate will be formed at the carbonyl group position, resulting in a product like this:

I know that the gem-diols are usually stablized by H-bonding, as is the case here as well (between the lower hydroxy and left acid group). I can also see that loss of the $\ce{H+}$ ion from the carboxylic acid group on the left will create an $\ce{O-}$ ion which will have an even stronger H-bonding. However, I am not sure how I can use this fact to relate the given $\mathrm{pK_a}$ values and the expected $\mathrm{pH}$ range.
I need help completing my train of thought. Thank you!


texts: Does esterification require reactants to be present in the same plane?

texts:
I believe that the first step is the Cannizzaro reaction which will give (c) as a product.

But since we are also adding $\ce{H+}$ in the second step, shouldn't an esterification reaction take place? That would give (d) as a final product.

However the answer given is (c).
My only guess as to why esterification wouldn't take place is the fact that the phenyl groups are in perpendicular planes, therefore esterification is difficult?
Is it necessary to have all the reactants in a plane for esterification?


texts: How to find if the unpaired electron is placed in hybrid orbital or pure orbital in odd electron species?

texts:
Odd electron species contain an unpaired electron which can either be placed in hybrid orbital or in pure orbital.

Example: In the case of $\ce{.CF3}$ radical, the unpaired electron is placed in $\mathrm{sp^3}$ hybrid orbital of carbon.

In the case of $\ce{.C(CH3)3}$ radical, the odd electron is placed in pure p orbital of carbon.

How do we determine whether the unpaired electron is placed in hybrid orbiral or pure orbital? What factors govern the same?


texts: How to know the kinetic rate of one reaction from 3 tests with different concentrations?

texts:
Recently, I've run an experiment about the effect of reducing concentration on rate of a reaction.
Here's the chemical reaction:
$\ce{10 NaHSO3 + 4 KIO3 ⇌ 5 Na2SO4 + 2 I2 + 3 H2SO4 + 2 K2SO4 + 2 H2O}$
I ran three tests:

$10$ cc $\ce{KIO3}$ Solution + $10$ cc $\ce{NaHSO3}$ solution _ Time: $163$ sec

$10$ cc $\ce{KIO3}$ Solution + A $6$ cc $\ce{NaHSO3}$ and $4$ cc water solution _ Time: $320$ sec

$10$ cc $\ce{KIO3}$ Solution + A $4$ cc $\ce{NaHSO3}$ and $6$ cc water solution _ Time: $713$ sec

I calculated the molarity of $\ce{NaHSO3}$ in each test and also calculated the rate of each test using the formula : $\frac{[\ce{NaHSO3}]}{t}$
Now the question is how can I know the kinetic order of this reaction?
I mean with only 3 numbers of concentration, I cannot draw a curve. Is there any other way to know the kinetic order?
Edit: I hope you already know that the curve of concentration according to time shows the kinetic order of reaction. It's just with 3 data you cannot draw an accurate curve.


texts: Amount of Energy Needed for Boiling a Litre of Water

texts:
What is the amount of energy (J or Wh) needed to boil one litre of tap-water in a regular kettle starting at room temperature (20°C)?

The calculation itself assuming ideal and standard prerequisites would be interesting as well as factoring in the non-purity of tap-water and a typical kettle performance factor.


texts:
In a science exhibition in 2011 , I and my  friend made a volcano that used vinegar and baking soda for the 'effects'. There was another group that made volcano too and they had brought their own supplies. But before the exhibition started, the members of other group came to us and asked us if we could share our baking soda because their baking soda wasn't 'working'. When I asked them why it wasn't working they told me that there wasn't 'salt' in it. (We were only 8-9 years old). When I tried using it it was forming bubbles but very slowly. Eventually our supplies ran out before the exhibition was over. One of my friends suggested that we should use chalk powder instead of baking soda(I don't know how he figured it out at age 9). So we ground up chalks and tried using it. In this case , it was just like the baking soda that didn't work , it was producing bubbles ,but very slowly.
What could be the issue in the two cases? Was it a matter of purity?
We had used synthetic vinegar used for food purposes(5-10%)(There was no issue with the vinegar because it worked well with our own baking soda). The chalks were ordinary chalks used in classrooms. Regarding the other group's Baking soda I do not have any other information cause it happened 10 years earlier.(And I'm no longer in contact with them)
Was reaction less fast in case 2(Chalk powder) because of the low solubility product of Calcium carbonate? But Solubility product is a thermodynamic factor and not a kinetic factor right ?


texts: Is there any explosion hazard with an enclosed graphite crucible melting silver?

texts:
the crucible volume is about 2 ounces.   The final design of the crucible will be enclosed tightly except for a small .5mm diameter hole at the bottom and a 1mm diameter hole at the top through which silver solder will feed.

I was wondering.  In my experiments should I worry about the thing exploding?


texts: "No variables in Z-matrix" error in scan calculation of Gaussian

texts:
I asked a similar question earlier this year but I'm still stuck with a similar problem.

Basically I'm trying to implement a scan calculation using both a z-matrix and Cartesian coordinates. I have the optimized Cartesian coordinates for a nanotube and z-matrix for benzene; I would like to set up the calculation to calculate the potential energy of the system when the benzene molecule is a distance R away from the NT along the z-axis. I'm trying to scan from 2.5 to 5.5 angstroms in 0.1 A intervals.

I've read the Gaussian documentation and it seems like mixing Cartesian and z-matrix coordinates in a scan function is possible but I've tried many different inputs and I still get a "No variables in Z-matrix error."

Here is a my current input file

%mem=40GB
%nproc=4
#P BP86/6-31G scan

Scan using 1 unit nanotube with benzene at 2.5 A

0 1
[Nanotube Cartesian coordinates]

X
X 1 R1
C 2 XC 1 A1
C 2 XC 1 A1 3 60.0
C 2 XC 1 A1 4 60.0
C 2 XC 1 A1 5 60.0
C 2 XC 1 A1 6 60.0
C 2 XC 1 A1 7 60.0
X 3 R1 2 A1 1 0.0
H 3 HC 9 A1 2 180.0
H 4 HC 3 A2 2 180.0
H 5 HC 4 A2 2 180.0
H 6 HC 5 A2 2 180.0
H 7 HC 6 A2 2 180.0
H 8 HC 7 A2 2 180.0

Variables:
R1 2.5 25 0.1

Constants:
XC=1.39893
HC=1.09100
A1=90.0
A2=120.0

System in consideration

Visualization of the z-matrix

Some questions:

Is there an issue with the route section? I tried replacing "scan" with "opt=modredundant" but that introduces its own errors and its clear I don't know what I'm doing.
I suspect this is a syntax issue since the documentation for "z-matrix" and "scan" suggests it is possible to keep the nanotube coordinates frozen and just scan the benzene molecule. Is there an issue with my variables and constants section? I've looked at many sample calculations but I didn't find any that consider moving one molecule toward another. If someone can link me to relevant literature regarding (reaction coordinate calculations?) I'm more than willing to look into it; as for now this is the method my professor suggested.


texts: Electric glow discharge of last 2 noble gasses

texts:
Radon is an extremely unstable noble gas. Due to this, putting it in a gas discharge lamp for a prolonged period of time is extreme hard, as pure radon is needed to give a true color, but radon decays quickly into other stuff, contaminating the lamp. But suppose we were to find a way to not let radon decay,  concentrate it in a gas discharge lamp, and turn the lamp on. What color would the radon gas glow?

Sources I find are contradictory. Here, it says

  Radon is said to glow red in discharge tubes

and the image that it gives

  is only an illustration, not radon itself.

Wikipedia says that it "glows green or red in discharge tubes", but it doesn't cite any sources there.
The spectral lines of radon are listed here. According to this source, radon gives probably somewhat reddish due to the strong lines at 705 and 745 nm.

Here it says that

  Radon glows violet/purple when discharged. The reason why is simply we can infer it off of the patterns of the periodic table. You see, radon is at the very bottom to the right, in the noble gases column. Noble gases are already stable (for the most part) and do not want to react with other particles; thus requiring a lot of energy to react. Radon being the largest natural noble gas element, us humans can mess with it a little bit more than its other noble gas brethren. Now since we know it requires a lot of energy to react, we know it is related to a light with an insanely short wavelength (shorter wavelength=higher energy). If we look at the light spectrum we can see the shortest wavelength and highest energy wavelength is purple/violet/indigo. Thus making radon that color when discharged.

And based on this emission spectrum, it appears that radon would fluoresce with a deep bluish-violet color.

Same question for oganesson. Although wikipedia says it should be a solid due to relativistic forces, what color would oganesson glow in a gas discharge lamp?


texts: Why is resonance possible in phenoxide anion as when the electron pair of oxygen is involved in conjugation we have 4 pairs of electrons in resonance which should imply that the ring has become anti aromatic and hence no resonance should be possible?


texts: Magnetic couplings using DFT in a spin frustrated system

texts:
I’m working with a trimeric copper system that have the classic triangular shape and experiences spin frustration. This is my first time dealing with such system and, so far, from what I’m reading, I know that the spins resonate between ↑↑↑ ↔ ↑↓↑ ↔ ↑↑↓ and that the triangle have couplings $J1_{ab}$, $J2_{bc}$ and $J3_{ca}$.

My question is: how it is possible, using DFT, to obtain the three magnetic couplings ($J1_{ab}$, $J2_{bc}$, $J3_{ca}$)? I’m supposing that the strategy of breaking the molecule in three dimers and calculating a broken-symmetry is not going to work, right?

Thanks in advance

P.S.: I’m doing my calculations using the ORCA package.


texts: Are there any stable complexes where an (N-unsubstituted) imine is bound eta^2 to a (late) transition metal?

texts:
I've been looking for an example of a stable complex where a $\ce{C=N}$ is coordinated $\eta^2$ to a (late) transition metal, but could not find any. Do they exist at all?

For $\ce{C=C}$ there are countless examples, Zeiss' salt, $\ce{Ni(COD)_2}$, etc.

If no or only very few $\ce{C=N}$ analogs exist, what's the reason?


texts: Effect of concentration on rate of reaction

texts:
I came across this problem:

  The $\ce{2NO + Br2 -> 2NOBr}$ follows the mechanism below:

  $$
\begin{align}
\ce{NO + Br2 &-> NOBr2} & &\text{fast} \tag{1} \\
\ce{NO + NOBr2 &-> 2NOBr} & &\text{slow} \tag{2}
\end{align}
$$

  If the concentration of both $\ce{NO}$ and $\ce{Br2}$ are increased two times the rate of the reaction would become

  A) 4 times
  B) 6 times
  C) 16 times
  D) 8 times

Now I know that overall order of a reaction is equal to the molecularity of the slowest step, hence order is 2 and since the concentrations of both the reactants are being increased by the same factor, i.e. 2 , the rate should be $2^2$ times irrespective of what is the order with respect to any reactant.

But the answer given is 8. How is this possible?


texts: Changes of Internal Energy un open system

texts:
My professor says the internal energy of a system can be calculated as $U=n T c_v$. Now I always thought that we could only calculate a change in internal energy $\Delta U = n c_v \Delta T$.

Following this idea, he says that a recipient that contains gas and loses a certain number of moles at constant temperautre undergoes a change in internal energy of $\Delta U = T c_v \Delta n$.

I've never seen any of this in any book. I believe he is assuming that the internal energy at 0 Kelvin is zero, which I believe is not true. However, in the case of the recipient losing gas,I wouldn't know how to calculate $\Delta U$.

Any thoughts? thanks!


texts: How can inconsistencies in these sodium chloride solutions be explained?

texts:
I'm entirely chemically-naive and am confounded when trying to convert $\ce{NaCl}$ brine concentrations to moles per litre.

The situation is that I'm performing linear multiple regressions using published data form multiple studies. Because the studies report their brine concentrations using different units I am trying to convert all of the concentrations into molarity (moles per litre). To do that I'm using the conversion tool at EndMemo - here's a screen shot:

But in more than one place in the literature people report different M values ... for example, below is an extract from one of the studies. Their M values don't match what I'm getting using the online converter (for example, 4 g/L $\ce{NaCl}$ is coming out as 0.068 M/L...hopefully I'm missing something very basic here?)

(Broseta D., Tonnet N., and Shah V., Geofluids, 2012, 12 (4), 280-294.)

As an aside, I'm not finding consistency with the unit symbols for Molarity and litre (sometimes they are capitalised, sometimes they are not...are they referring to different things or is this another example of inconsistency)?


texts:
How can I estimate the $E_{0-0}$ value of an organic dye? I have obtained the UV-vis absorption and fluorescence spectra of this dye in solution. This article talks about (in Table 2 notes) the intercept between the normalized absorption and emission spectra, but I don't quite understand what they mean.

Does someone here know? Attached is the (non-normalized) spectra.


texts: Does anyone know the meaning of these two bonds in stereochemistry? These bonds are provided by the $\mathrm{\LaTeX}$ chemfig package. The creator of the chemfig package describes them as "hollow cram bonds".


texts: Is there an actual distinction between through-space charge transfer and excimer emission?

texts:
Variety of books and literature reviews consider excimer (or exciplex) emission something distinct from through-space charge transfer. Is this actually the case?
This question arises, because the more literature I read on this subject the less sure it seems to have any distinctive characteristics one from another. Mainly because the same ''evidence'' (e.g. the bathochromic shift of emission, lifetime increase, concentration studies) is used to argue for excimer or exiplex emission in one study, while other authors propose that such evidence supports CT emission.


texts: In 1961, thalidomide was first introduced as an over-the-counter cure for morning sickness. Pregnant women across the country began to take the drug, which worked well, but shortly after, babies began to be born with severe birth defects. Experts linked this to thalidomide and later discovered that the r-enantiomer, which was the cure for morning sickness, underwent a certain reaction (or reactions) within the body that could change its configuration to that of the s-enantiomer. Does anyone know the steps of this reaction or at least what it is called?


texts: Why is the letter J omitted in the spdf... sequence?

texts:
Under spherical symmetry, the irreducible representations corresponding to $L = 0, 1, 2, \cdots$ are assigned the letters $\mathrm{S}, \mathrm{P}, \mathrm{D}, \mathrm{F}, \cdots$ after which the letters progress in alphabetical order. (The familiar names of the atomic orbitals are also labelled with this sequence of letters.) Therefore, we have:

$$\mathrm{S}, \mathrm{P}, \mathrm{D}, \mathrm{F}, \mathrm{G}, \mathrm{H}, \mathrm{I}, \mathrm{K}, \cdots$$

but as far as I can tell, $\mathrm{J}$ is conspicuously omitted. I am guessing there is a reason behind this - what is it? Is it to avoid confusion with some other $J$, like the total angular momentum quantum number $J$, or is it perhaps based on some typographical argument (J being easily confused with I)?


texts: Why boron trihydride is weaker lewis acid than boron tribromide and boron tri-iodide?

texts:
There is no back-bonding in case of boron trihydride so it is a stronger lewis acid than boron trichloride ( even though chlorine atom is more electronegative than hydrogen atom).

Then  why boron trihydride is weaker lewis acid than boron tribromide and boron tri-iodide?


texts: What does the slash in polymer nomenclature, e.g. Acrylates/ Beheneth-25 Methacrylate Copolymer, mean?

texts: I was given a task to find SDS-Sheets for polymers/microplastic particles in cosmetics and I am confused, since there are often two chemicals divided by "/", e.g. Acrylates/ Beheneth-25 Methacrylate Copolymer. So would it be correct to look for the SDS-sheets for the both of them separately? Is it just the mixture of the two? Maybe someone can provide me with some information of how I am supposed to read these kinds of names.


texts: Can bis-quaternary aromatic compounds act directly on acetylcholine receptors?

texts:
The book Cholinesterases and Anticholinesterase Agents gives examples of bis-quaternary aromatic compounds that are capable of inhibiting acetylcholinesterase. Page 400 gives examples of some such compounds, designated 2842CT, 3443CT, 3116CT, 3152CT, and 3113CT. The first three are neither organophosphates nor carbamates, while the last two are carbamates. The book goes on to list other bis-quaternary aromatic compounds that have anticholinesterase activity, but does not mention whether they can act directly on acetylcholine receptors. Are they capable of acting on ACh receptors directly, whether as direct agonists or antagonists?

Reference:
Koelle, George B. Cholinesterases and Anticholinesterase Agents. Springer Berlin, 2013.


texts: Should cyaphide create similar chemical compounds as cyanide?

texts:
The cyaphide anion $\ce{(CP)-}$ should be chemically similar to its nitrogen analogue cyanide. $\ce{(CN-})$ But unlike it's counterpart it readily polymerizes  so it has only been found in outer space naturally. However, it should form compounds that should be the same  like cyanides.For example sodium cyanide ($\ce{NaCN}$),would be called sodium cyaphide ($\ce{NaCP}$) and hydrogen cyanide ($\ce{HCN}$) would be called hydrogen cyaphide or as it's called methylidynephosphane ($\ce{HCP}$) and the anions: phosphaethynolate (cyaphate) ($\ce{PCO-}$) and thiophosphaethyonlate (thiocyaphate), ($\ce{PCS-}$) and also potentially the cyaphogen ($\ce{P2C2}$) have been observed but as far as I know the only reliable info I found on cyaphides were on Wikipedia and they were very short as well. Which source on information do I go with?
More information: https://en.wikipedia.org/wiki/Methylidynephosphane


texts: Why is Sonogashira's coupling more feasible than Hiyama's coupling when both could occur? I have seen many examples in syntheses, here is one (the penultimate reaction):


texts:
In the following reaction, Hofmann elimination is preferred.

This reaction takes place by E1 mechanism. I thought the Zaitsev product would be major due to 1 extra hyperconjugating structure. In the book, it is given that it is due to sterically compressed alkene, so Hoffmann product is major. I am unable to understand why the sterical hinderance would lead to the instability in alkene as the three methyl groups is one bond away from alkene.


texts: Why is it that adding $\ce{SiCl4}$ will cause the pH of a solution to become acidic? I thought that only salts (ionic bonds break in water) can change the pH once dissolved in water. $\ce{SiCl4}$ has covalent bonds, so why does the pH change?


texts: How does the pressure change in the dimerization of nitrogen dioxide?

texts:
say we have a reaction N2O4 reversible 2NO2

for this reaction,if initial number of moles of N2O4 is 'a' can we write

t = 0 a -

at equilbrium a-x 2x

similarly can we do the same for pressure? i.e.
if initial pressure is p,then can we say?

t=0           p -

at equilbrium p-y 2y

if yes why? and is x=y,i.e is the number of moles of x dissociated equal to decrease in pressure of reactant?
and is this method valid for all reversible reaction irrespective of the stoichiometric coefficient of reactants and products


texts: How to Run GAMESS and Avogadro on Command Line?

texts:
I always use GAMESS and Avogadro on my own laptop. Recently I installed them on our university supercomputer and started using them by remote logging-in.

On the laptop everything was super easy but unfortunately I can not find any documentation for using them from Terminal Command Line ( I mean sending a job and receiving the result all from Terminal Command Line ).

It would be great if someone knows a good documentation or tutorial for this subject.


texts: Radon gas in earthquake prediction - Why Rn?

texts:
I recently studied an article about predicting earthquakes and how correctly realizing that an increase in $\ce{Rn}$ gas is a sign for the earthquake saved a whole city. The following is derived from the wikipedia page for earthquake prediction:

  There are reports of spikes in the concentrations of such gases prior to a major earthquake; this has been attributed to release due to pre-seismic stress or fracturing of the rock. One of these gases is radon, produced by radioactive decay of the trace amounts of uranium present in most rock.

  Radon is useful as a potential earthquake predictor because being radioactive it is easily detected, and its short half-life (3.8 days) makes it sensitive to short-term fluctuations. A 2009 review found 125 reports of changes in radon emissions prior to 86 earthquakes since 1966.

However, wikipedia then attempted to prove that most of the assretions related to radon are false statements,

but all this leaves me with one question: Why radon? (Why isn't another chemical species used for identifying the danger of feasible earthquake?) Maybe things I studied were too technical for me to understand, so please be as simple as you can be.

(Feel free to edit tags)


texts:
We have arrange the followig sequence  for decreasing order of ionic radius .

$Se^{-2},I^-,Br^{-},O^{-2},F^{-}$

In my book the answer given as
$I^{-},Se^{-2},Br^{-},O^{-2},F^{-}$

But according to me $O^{-2}$ should be greater than F$^-$

As oxygen has two more electrons , so its zeff should decrease more in comparism to fluorine


texts: How long does a linear hydrocarbon chain have to be before we call it polyethylene?

texts:
Might be a really silly question here but here goes. Polyethylene is a polymer with a repeating unit of just 2 carbon atoms attacked to 2 hydrogens each which connect to other repeat units.

This structure is just an aliphatic hydrocarbon like butane or hexane or decane etc. My question is, at what carbon chain length does a hydrocarbon cease to be a normal alkane but instead becomes a polymer?


texts: Why does silver oxide form a coordination complex when treated with ammonia?

texts:
Part of the preparation of Tollens' reagent occurs according to the formula:

$$\ce{Ag2O (s) + 4 NH3 + 2 NaNO3 + H2O → 2 [Ag(NH3)2]NO3 + 2 NaOH}$$

I wonder how exactly the oxygen gets "unstuck" from the silver under the influence of ammonia. I've read about coordination complexes, so I understand what $\ce{[Ag(NH3)2]NO3}$ is, but I'm puzzled at what exactly happens to pull that oxygen apart from $\ce{Ag2O}$

I've done very little exploration of the issue, so this may be too basic a question - in which case just please give a hint on what to read up.

I found this (now deleted) comment:

  $\ce{NH3}$ dissolves silver oxide because the nitrogen has a pair of electrons that it can share with the silver forming a diammine complex. It has nothing to do with pH adjustment. – A.K. Jan 20 '16 at 17:17

Chemguide states this:

  This is made from silver(I) nitrate solution. You add a drop of sodium hydroxide solution to give a precipitate of silver(I) oxide, and then add just enough dilute ammonia solution to redissolve the precipitate.


texts: How to prove that the forward and reverse reactions have the same rate at equilibrium?

texts:
I was trying to answer a question from Zumdahl and Zumdahl's Chemistry textbook which asks me to show that the rate constant K is related to the forward and reverse reaction constants:
$$K=\frac{K_\mathrm{f}}{K_\mathrm{r}}.$$

In answering the question it is given that:
$$K_\mathrm{r}=Ae^{\frac{-(E_\mathrm{a}-\Delta G)}{RT}}$$

And something is lacking in my understanding here. As I understand it the activation energy of the reverse reaction is equal to $E_\mathrm{a}$ of the forward reaction plus the free energy. That takes you back to the transition state - but the transition state is defined as the point at which products always become reactants, so how are reactants being formed from the products?


texts: How can you tell when a molecule forms a lattice

texts: I came across the molecule SiO2 and didn't realize that in fact, it forms a lattice. How could I have found out that, in fact, it forms a lattice?


texts: How to calculate the pH of a buffer after dilution

texts:
You have a beaker containing $\pu{542 mL}$ of a solution of $\pu{0.48 M}$ acetate buffer ($\mathrm{p}K_\mathrm{a} = 4.76$) at $\ce{pH 4.2}$. To this solution, you add $\pu{342 mL}$ of pure water. What is the $\ce{pH}$ of the resulting solution?

The answer is $4.6$. However, I do not know how to arrive at that answer. I know the H-H equation must be used:

$$\ce{pH} = \mathrm{p}K_\mathrm{a} + \log\frac{[\ce{A-}]}{[\ce{HA}]}$$


texts: What makes concentrated aqueous solutions of aluminium nitrate and aluminium chloride suitable to dissolve noble metals, specifically gold?

texts:
Aluminium nitrate is a strong oxidising agent and aluminium chloride acts as a Lewis acid. Also these solutions are claimed to have the abilities of aqua regia and therefore can dissolve noble metals.
References

Dissolution of noble metals in highly concentrated acidic salt solutions
Federica Forte, Sofia Riaño and Koen Binnemans, Chem. Commun., 2020, 56, 8230-8232, DOI: 10.1039/D0CC02298E
Dissolving Noble Metals without Aqua Regia,  David Bradley, Chemical Communications/Royal Society of Chemistry, 04 August 2020 DOI: 10.1002/chemv.202000071


texts: Beckmann rearrangement v/s dehydration of Oximes

texts: In the above question, A is an oxime, which is then reacted with phosphorus pentoxide. Now, phosphorus pentoxide is both a dehydrating reagent and a reagent used for Beckmenn rearrangement, but which reaction will form the major product mostly, ie, which reaction will dominate? My teacher told to consider beckmenn rearrangement with Phosphorus pentoxide, but the answer of this question is A, that is, dehydration is favored . What I think from my experience is that aldoximes will favor dehydration, and ketoximes beckmenn rearrangement( dehydration obviously cannot  occur in them), but I am not sure. Please tell the conditions under which any reaction will dominate over other. Also what  would be the answer if phosphorus pentoxide is replaced by phosphorus pentachloride?


texts:
If I have the amount of the molecule in moles, how do I calculate the mass of an individual molecule?

For example, if the molecule was water?


texts: Are phenyl and allyl groups in prop-2-enylbenzene coplanar?

texts: Wouldn't C1 and C2 in prop-2-enylbenzene be on the same plane as that of the phenyl ring, right? If the double bond connected to C2 was between it and C1, they would be, but is it correct that now they're both planar, but on different planes?


texts:
The boiling point of a substance $X$ at 1 atm pressure is $500 k$ . The enthalpy of vapourisation at the boiling point of $X$ (l) is 80 kj/mol .The molar specific heat of $X(l)$ = $5 × 10^{-3}$ kj/mol and $C_p$ of X(g) = $5 ×10^{-4}$ kj/mol
What is the molar latent heat of vapourisation of $X(l)$ at $800 K$ and at $1 atm$ ?

Options :
A: lesser than $80 kJ$ $\\$
B: greater than $80 kJ$ $\\$
C : equal to $80kJ$ $\\$
D: Since 800K is the higher temperature than the boiling point of $X(l)$ ; therefore , enthalpy of vapourisation is not applicable


texts: Regioselectivity in Electrophilic Aromatic Substitution of Pyrrole and Indole

texts:
If we look into the structures of Pyrrole and Indole, they are very similar. Only Indole has one extra Benzene ring attached to it, i.e. if we attach one Benzene ring to Pyrrole, what we'll have is nothing but Indole.

But if we delve into the preferable positions of Electrophilic Aromatic Subsitutions for these compounds, it's pretty well known that Pyrrole undergoes EAS preferentially at the $2$-position, whereas for Indole it's the $3$-position which is favoured.
A typical example of an Elcetophilic Aromatic substitution reaction where this distinct feature between Pyrrole and Indole can be clearly visible is the Vilsmeier-Haack Reaction. The major outcomes of the reaction in the two cases clearly show the difference.

Now, the preference of $2$-position in case of Pyrrole can be justified easily by considering the greater stability of the $\sigma$-complex intermidiate formed in case of substitution at $2$-position due to more number of resonating structures as clearly been described in the answer to the question Regioselectivity in Electrophilic Substitution of Pyrrole
Now my question is, applying the similar logic Electrophilic substitution at the $2$-position should be even more favoured in case of Indole, as the $\sigma$-complex in that case should be further more stabilised due to resonance with the Benzene ring as well. Therefore, the preference of substitution at $2$-position should be exceptionally higher than at $3$-position in case of Indole. But in reality, it's actually the opposite. Why is this anomaly observed in case of Indole ?
The resonating structures in case of two different substituent positions in Indole are shown below,

P.S. Thoughtful answers are highly appreciated. Any kind of Quantum Mechanical Calculations or Computations or Orbital Analogy are also welcome.


texts: Why does the pH rapidly increase near the equivalence point during--why does the slope of the graph of a pH curve sharply increase around this area?


texts:
I was cleaning my blinds today, and wanted to know what the primary components of dust are. I know that it is made of microorganisms and other particles, but I do not want to guess that it will be $\ce{N}$ or $\ce{Si}$.

I can guess that other materials outside our house might have more than one component for dust. But what about inside the house?


texts: Reaction of glucose acetal with acetic anhydride

texts:
The following problem was asked in JEE Mains 2020 (Sept 2, Shift 1),

Consider the following reactions:
$\ce{ (i) Glucose + ROH ->[dry HCl] Acetal ->[$x$ eq. of (CH3CO)2O] acetyl derivative }$
$\ce{ (ii) Glucose ->[Ni/H2] A ->[$y$ eq. of (CH3CO)2O] acetyl derivative }$
$\ce{ (iii) Glucose ->[$z$ eq. of (CH3CO)2O] acetyl derivative }$
What are $x, y,$ and $z$ in these reactions, respectively?

I know that the reaction in (i) is acetal formation (used to protect aldehyde), and that alcohol reacts with anhydrides to form acids. As, there are only 5 hydroxyl group in acetyl deriv. of (i), so $x=5$.
In (ii), carbonyl part of glucose reduces to hydroxyl group, so $y=6$. And, in (iii), glucose directly reacts with anhydride, so $z=5$.
But, my answer was wrong (x only), as per the key. What am I doing wrong?

The answer given is,

 x = 4, y = 6, z = 5


texts: How does different pH affect copper electroplating

texts:
I'm currently investigating the effect on the concentration of hydrogen ions in the copper sulfate solution on the amount of copper deposited on the cathode within a certain amount of time.

I've been trying to find an answer online but have had no luck in getting a clear cut answer. I was wondering if there is anyone here willing to provide me with some insight or a suggestion for the method to carry out this experiment.


texts: Importance of zinc blende and wurzite crystal structures for semiconductors?

texts:
I am currently studying the textbook Physics of Photonics Devices, Second Edition, by Shun Lien Chuang. In a section discussing the basic concepts of semiconductor band and bonding diagrams, the author gives the following description:

The basic idea is that for a semiconductor, such as $\ce{GaAs}$ or $\ce{InP}$, many interesting optical properties occur near the band edges. For example, Table 1.1 shows part of the periodic table with many of the elements that are important for semiconductors, including group IV, III-V, and II-VI compounds. For a III-V compound semiconductor such as $\ce{GaAs}$, the gallium ($\ce{Ga}$) and arsenic ($\ce{As}$) atoms form a zinc-blende structure, which consists of two interpenetrating face-centered-cubic lattices, one made of gallium atoms and the other made of arsenic atoms (Fig. 1.1).

This seems to be the relevant Wikipedia article for zinc-blende (Zincblende) structure.
I was interested in understanding the relevance of this structure to semiconductors, so I did further research. I then came across this website, which says the following:

Here are the two most important crystal structures for semiconductors.
They are often referred to by the historical names "Zinc blende" from the German "Zinkblende" $= \ce{\alpha-ZnS}$, a rather ubiquitous mineral. The name "Sphalerite" also comes form the German: "Sphalerit", which, as was the custom of the time, stems from the Greek "sphaleros" meaning treacherous or malicious because it is easy to confuse it with other minerals.
Wurtzite was and is the name of the $\ce{\beta-ZnS}$ modification - the hexagonal high-temperature variant. The named after the French chemist C. A. Wurtz (* 1817, † 1884), which gives us an idea of how old those names are.
Zinc blende or sphalerite or Diamond structure

Wurtzite or hexagonal structure
Red lines are not showing bonds.

However, this website does not actually explain why these are the two most important crystal structures for semiconductors. I was wondering if someone would please take the time to explain this.
EDIT:
Thinking about Justanotherchemist's comment and Oscar Lanzi's answer, I wonder if all group $\ce{III-V}$ semiconductors have these $\ce{ZnS}$ structures? Because, if so, then that could very well be the answer to my question here, since, as I understand it, group $\ce{III-V}$ semiconductors are the most important semiconductors for practical purposes? As Oscar Lanzi said in his answer, not all semiconductors have a $\ce{ZnS}$ structure, so the answer cannot be that they are the most important because all semiconductors have a $\ce{ZnS}$ structure.


texts:
I was reviewing the thermodynamics of micelle formation from the Wikipedia page and this book. I understood most of the arguments but micellization is supposed to be an entropy driven process with a positive entropy change in the process of micellization. But isn't this a bit counter-intuitive?

  In the unassociated form, the surfactant molecules are free to roam
  about in the solution much like normal solutes. But in the form of a
  micelle, they get associated, grouped into an associated whole, which
  reduces the freedom of independent movement and should therefore
  decrease the entropy (randomness) of the system? The entropy change
  should be negative during micellization. Why is it positive?

I understood the mathematical arguments leading to the develpment of the approximate formula $\Delta G=RT\ln(\text{CMC})$.


texts: Log(Q) is zero, therefore the effect of temperature change is unaccounted for by Nernst Equation?

texts:
I have an internal assessment on Nernst Equation. The experiment is seeing how changing temperature effects cell potential. The solution are zinc and copper sulfate with each having concentration of 1M.

I have read online on many sources that Q in the Nernst equation is calculated based on the initial concentration values. In my case that is 1M for both the product and the reactant, hence Q=1 and log(Q)=0. If log(Q)=0, then the whole left part of the Nernst equation(E=E°-RT*log(Q)/nF) is equal to zero (E=E°-0) and therefore E=E°. However, I have changed the temperature and my experimental results do show a change in cell potential with changing temperature, but how can I calculate that change in cell potential with changing temperature theoretically.

Thank you.


texts: A good textbook to balance chemical equations?

texts: Is there any good textbook which after reading it I would be able to balance almost any chemical equation in inorganic chemistry?


texts: How to do Lowdin symmetric orthonormalisation?

texts:
Löwdin symmetric orthonormalisation seems to be a common practice in quantum chemistry. I come from a different background though and have to understand it and possibly implement in a computer code. Here is the definition of the transformation;

$$
|{\phi'}\rangle = S^{-1/2}|\phi\rangle,
$$

where $S$ is the overlap matrix between the non-orthogonal basis,

$$
S = \left< \phi|\phi \right> .
$$

My first question is how to obtain $S^{-1/2}$ analytically?
Are there any parallel algorithms available to compute it numerically?


texts: Is that true that if we reduce the Cl in water will reduce the saltiness of water?

texts:
I just move to some place near the ocean and I dig a weld and the water taste is a little bit salty (not as salty as sea water but there are salty taste). Then, I bring the water to the lab and there are 2 points that are really high the TDS $3345\,\mathrm{mg/litre}$, and $\ce{Cl-}$ $998\,\mathrm{mg/litre}$.

I already use a softener to reduce the $\ce{CaCO3}$ and magnesium content, and now my water treatment guy that install the first softener suggest me to add another filter that contain resin and can absorb $\ce{Cl-}$ content, he said to me The resin will absorb the $\ce{Cl-}$ content and make the water taste better. He also said that it will need $\ce{HCl}$ or $\ce{(NH4)2 SO4}$ to regenerate the resin.

My question is:

1. Is that true that we can reduce the saltiness in water if we remove the $\ce{Cl-}$ ?

2. What kind of resin this water treatment guy talking about? Is this resin even exist?


texts:
A question in Thermodynamics of Natural Systems by G. M. Anderson is to find the "standard heat of reaction" of this reaction:
$$\ce{C8H16N2O3(aq) + H2O(l) -> C6H13NO2(aq) + C2H5NO2(aq)}$$

As far as I understand it, it should be a rather simple problem of finding $\Delta_\mathrm r H$.
So it should be:

$\Delta_\mathrm r H=\Delta_\mathrm fH (\ce{C6}) + \Delta_\mathrm fH (\ce{C2}) - \Delta_\mathrm fH (\ce{C8}) - \Delta_\mathrm fH (\ce{H2O})$ (note that I shortened the organic formulae)

According to the data from the same textbook, it's:
$(-632077~\pu{J/mol}-513988~\pu{J/mol})-(-847929~\pu{J/mol}-285830~\pu{J/mol})=-12306~\pu{J/mol}$

However, the answer given is $−89475~\pu{J/mol}$.

Am I missing something? Do I need to add some terms of pressure or volume expansion? Is this not the enthalpy that I'm looking for?


texts: Chemical that will dissolve the oils left over from broken down coffee grounds?

texts: When coffee grounds breakdown in pipes there is a black sludge residue as a result. Is there a chemical that would dissolve this residue?


texts:
Question:

  Prior to 1961, the atomic mass unit was defined as 1/16 the
  mass of the atomic mass of oxygen; that is, the atomic mass
  of oxygen was defined as exactly $\pu{16 amu}$. What was the
  mass of a $\ce{^{12}C}$ atom prior to 1961 if the atomic mass of oxygen on today’s scale is $\pu{15.9994 amu}$?

I don't fully understand the logic behind the question. Here's my thinking. Atomic mass of all substances were related to $\pu{16.0000 amu}$ prior to 1961. Therefore, we can make the following expression where $X$ is mass of $\ce{^{12}C}$
$$\dfrac{X}{\pu{16.0000amu}}$$

Today, all atomic mass is related to $\pu{12.0000 amu}$ of $\ce{^{12}C}$. We can model the relationship as $$\dfrac{\pu{12.0000amu}}{\pu{15.9994amu}}$$

What the solution manual does is make the two equations equal to each other and solves for $X$.

$$\dfrac{X}{\pu{16.0000amu}}=\dfrac{\pu{12.0000amu}}{\pu{15.9994amu}}$$

How are we justified in doing this?


texts: How to extract wavefunction from GAMESS output?

texts:
Is there a way to extract the molecular wavefunction from GAMESS output?

I know there are packages that can extract the eigenvalues or the exponents and show them as a table but that is not of much help as anyone can easily find those values in the output file by looking at the numbers.

What I am looking for is the complete wavefunction equation. Is there such a package or something available. Something like this simple extractor I have written for STO-3G (this is just a very primitive one that only works for small STO-3G outputs ) :


texts: Solution of very small particles with neutral buoyancy and distinguishable to the naked eye

texts: I'm trying to study the Tea leaf paradox, and asked a question about it on physics.stackexchange.com. To get further on the problem, I want to make a solution of very small objects in water that are distinguishable to the naked eye, and have (very close to) neutral buoyancy. I teach at a high school and have access to the chemistry lab here. Suggestions?


texts: The charge to mass ratio of an electron is -1.7588×10^8 coulomb/g, and is fixed. My textbook, however says that as the speed of an electron increases, the value of charge to mass ratio increases. How is this possible? Shouldn't the mass and charge of an electron always be the same? How is the ratio changing?


texts:
I am going to take PChem I in my biochem dept next sem, which is a watered down version of the PChem course in Chem dept. It basically covers thermodynamics and a little bit of quantum stuff. The syllabus says there is no required text, since course notes will be available once we register for class. But I do want to get ahead of class by reading books. I have several books at hand, please give me suggestions on which one should I use and if you have any good free lectures, feel free to post links as well.I don't feel like a need a Quantum Chem Book, given that how little quantum is actually covered.

Intro to Molecular thermodynamics by Hanson&Green, PChem for Chem and BioSci by Chang,Pchem by Castellan.Molecular Driving Forces by Dill&Bromberg, PChem: A molecular approach by McQuarrie, An introduction to thermal physics by Schroeder, Callen's thermodynamics text and also Fermi's.

Personally, I found Hanson, Castellan, Dill, and Chang are pretty good, haven't read any other


texts: Why is the solution of ammonium bifluoride more acidic than aqueous ammonium fluoride?

texts:
At low concentrations of aqueous $\ce{NH4HF2}$ $(w = 1–2\,\%)$ $\mathrm{pH}\approx 3.$
But aqueous $\ce{NH4F}$ $(w = 20–40\,\%)$ has $\mathrm{pH}\approx 7.$
Yet the equilibria of
$$
\begin{align}
\ce{HF &-> H+ + F-} &\quad K &= \pu{6.85E-6 M} \tag{1} \\
\ce{HF + F- &-> HF2-} &\quad K &= \pu{3.963 M^-1} \tag{2}
\end{align}
$$
I understand that $\ce{NH4F}$ comes from a weak acid and a weak base. So, the $\mathrm{pH}$ is around neutral. I don't understand how this equilibria makes $\ce{NH4HF2}$ more acidic. Does the second equilibria make the $\ce{HF2-}$ a stronger acid? I'm having a hard time understanding this.


texts: I am tying to determine if an acid is a liquid or aqueous solution? Please can some one enlighten me?


texts: Mechanism for conversion of ketone to dichloride with phosphorus pentachloride

texts:
I would like to know the mechanism of this reaction leading to the formation of a geminal dichloride. I am unable to predict how the $\ce{C=O}$ breaks and how the 2 $\ce{Cl}$ atoms replace the oxygen atom. What kind of a reaction is it?

Note: This reaction is mentioned on page 310 of Solomon and Fryhle's  Organic Chemistry in the chapter "Alkenes and Alkynes". It's the precursor of the preparation of cyclohexylacetylene through E2 mechanism using 3 equivalents of $\ce{NaNH2}$


texts: The effect of dilution on the rate of a system in equilibrium

texts:
I'm attempting to answer a question from my textbook, however the answer that the textbook provides doesn't make sense to me.
The question:

Laura, a VCE chemistry student, loves graphs and wanted to represent an equilibrium reaction by using graphs. The reaction she chose was:
$\ce{Fe^{3+}(aq) + SCN-(aq) <=> FeSCN^{2+}(aq)  \ \ \ \ \ \ \Delta H=-\nu e}$
Draw the rate-time graph for the reaction when the system is diluted at constant temperature.

In my mind, this dilution would instantly decrease the concentration of the reactants and products. But as it decreases the concentration of each species present by the same factor this will not disturb equilibrium, and simply result in a slower rate of reaction.
Given my assumptions I drew a graph where the forwards and reverse reaction both dropped vertically then continued on at the same, lower rate of reaction in equilibrium.
But the answer provided by the textbook is as follows

I just came across another question similar to this, and supposedly the system partially opposes the increase in concentration by favouring the reaction that produces the least amount of particles (in the same way as a change in pressure would cause the system to react). But if this is the case, and the concentrations are still balanced after the dilution, wouldn't it change the equilibrium constant? Which I have been told only temperature can change.
I'm assuming then that my understanding is flawed somewhere in regards to the system remaining balanced after the dilution, but I can't seem to see how diluting the system would unbalance the concentrations as they're all being decreased by the same factor.
Is the answer provided by the textbook wrong? Or is there something that I'm missing?


texts: Why are phosphonate-stabilised ylides used in HWE reaction more nucleophilic than phosphonium ylids used in Wittig reaction? Explanations without rationalisations using d orbitals would be welcome.


texts:
I've read that when a carboxylic acid reacts with $\ce{LiAlH4}$ the corresponding alcohol is formed:

But when I try to think of the mechanism, I get stuck here:

$\ce{LiAlH4}$ produces $\ce{H-}$. Since $\ce{H-}$ is a strong base it should immediately abstract a proton from the carboxylic acid to give the corresponding carboxylate ion (just like in the reaction of carboxylic acids with Grignard reagents), instead of undergoing nucleophilic addition to give the alcohol.

How do I resolve this?


texts: What do you mean by a pseudohalogen/pseudohalide and how do you tell whether a molecule/ion is a pseudohalogen/pseudohalide ?


texts:
I am currently studying the textbook Mass Spectrometry, third edition, by Jürgen H. Gross. Chapter 2.4.3 Bond Dissociation Energies and Heats of Formation says the following:

Energetics of $\ce{H}^\bullet$ loss from $\ce{CH_4^{+ \bullet}}$ The minimum energy needed to form a $\ce{CH_3^+}$ ion and a hydrogen radical from the methane molecular ion can be estimated from the heat of reaction, $\ce{\Delta H_r}$, of this process. According to Fig 2.6, $\ce{\Delta H_r} = \ce{AE_{(CH_3^+)}} - \ce{IE_{(CH_4)}}$. In order to calculate the missing $\ce{AE_{(CH_3^+)}}$ we use the tabulated values of $\ce{\Delta H_{f(H^\bullet)}} = 218.0 \ \text{kJ mol}^{-1}$, $\ce{\Delta H_{f(CH_3^+)}} = 1093 \ \text{kJ mol}^{-1}$, $\ce{\Delta H_{f(CH_4)}} = -74.9 \ \text{kJ mol}^{-1}$, and $\ce{IE_{(CH_4)}} = 12.6 \ \text{eV} = 1216 \ \text{kJ mol}^{-1}$. First, the heat of formation of the methane molecular ion is determined based on the experimental value of $\ce{IE_{(CH_4)}}$:
$$\ce{\Delta H}_{f(CH_4^{+\bullet})} = \ce{\Delta H_{f(CH_4)}} + \ce{IE_{(CH_4)}} \tag{2.14}$$
$$\ce{\Delta H}_{f(CH_4^{+\bullet})} = -74.9 \ \text{kJ mol}^{-1} + 1216 \ \text{kJ mol}^{-1} = 1141.1 \ \text{kJ mol}^{-1}$$
Then, the heat of formation of the products is calculated from:
$$\ce{\Delta H_{f(prod)}} = \ce{\Delta H_{f(CH_3^+)}} + \ce{\Delta H_{f(H^\bullet)}}  \tag{2.15}$$
$$\ce{\Delta H_{f(prod)}} = 1093 \ \text{kJ mol}^{-1} + 218 \ \text{kJ mol}^{-1} = 1311 \ \text{kJ mol}^{-1}$$
Now, the heat of reaction is obtained from the difference
$$\ce{\Delta H_r} = \ce{\Delta H_{f(prod)}} - \ce{\Delta H}_{f(CH_4^{+\bullet})} \tag{2.16}$$
$$\ce{\Delta H_r} = 1311 \ \text{kJ mol}^{-1} - 1141.1 \ \text{kJ mol}^{-1} = 169.9 \ \text{kJ mol}^{-1}$$
The value of $169.9 \ \text{kJ mol}^{-1}$ ($1.75 \ \text{eV}$) corresponds to $\ce{AE_{(CH_3^+)}} = 14.35 \ \text{eV}$, which is in good agreement with published values of about $14.3 \ \text{eV}$ (Fig. 2.7).

Note: The amount of energy needed to be transferred to the neutral $\ce{M}$ to allow for the detection of the fragment ion $m_1^+$ is called the appearance energy ($AE$) of that fragment ion.

Taking the values from Fig. 2.7 and using this calculator, we get that $1311 \ \text{kJ mol}^{-1} = 13.588 \ \text{eV}$ and $1386 \ \text{kJ mol}^{-1} = 14.365 \ \text{eV}$.
Unless I have made a mistake or am misunderstanding something, these values do not agree with what the author has presented. It seems that, if we take the values from Fig 2.7, the value of $169.9 \ \text{kJ mol}^{-1}$ ($1.75 \ \text{eV}$) corresponds to $\ce{AE_{CH_3^+}} = 13.588 \ \text{eV}$, which implies that the published value should be around $14.365 \ \text{eV}$.
So has the author made a small mistake here? Or am I misunderstanding something?
I would greatly appreciate it if people would please take the time to review this.


texts: Effect of quantum tunnelling on chemical reactions at very low temperature

texts: Can anybody give me a schematic representation of how quantum tunneling allows chemical reactions to occur at very low temperatures like in the interstellar medium.


texts: Precedence of 1,2 carbocation rearrangement

texts:
How can one choose which group has more shifting tendency in 1,2 carbocation rearrangement? The obvious order is via the stability of the carbocation of the group. But, phenylic groups have high shifting tendency--and a phenylic carbocation is unstable.

Is there a way of predicting these? I was thinking that it will be related to the delocalization in the triangular intermediate formed.

Update: I'm talking about comparing "migratory aptitude" of the $R$ groups in a system similar to $>C(+)-C(R_1R_2R_3)$


texts: Gibbs Free Energy of Solutes and Solutions

texts:
Using the equation $$\ce{CaSO4 (s) <=> Ca^2+ (aq) + SO4^2- (aq)},$$ and $\Delta H/\Delta S$ values, calculate $\Delta G$ at $50~^\circ\mathrm{C}$ when the solution is saturated with $\ce{Ca^2+}$ and $\ce{SO4^2-}$.

My Attempt
$$\Delta G = \Delta G^\circ + RT \ln Q$$
I calculated $\Delta G^\circ$ at $50\ \mathrm{^\circ C}$, But I am confused as to how we know what $Q$ is if there is no reactant then does $Q$ not become $\ce{[Ca^2+][SO4^2- ]/0}$, but this is impossible.


texts: Will Sodium Amide react with Epoxides in the same manner as Grignard Reagents?

texts: I have been unable to find the reaction anywhere on the internet so I'm assuming the answer is no, although I would like an explanation as to why.  I can't seem to find any reason why it would not work, provided the reaction is carried out in two steps.  In the first step, H2N:- will act as a nucleophile, attacking the least sterically hindered carbon of the epoxide.  The second step would of course be an acidic workup.  As stated in the question, I would expect the same exact mechanism as the reaction of Grignard Reagents with epoxides (substituting sodium amide as the nucleophile) due to the high basicity of sodium amide and Grignard Reagents.  Like I said, I'm not expecting the reaction to be viable.  However, I would like to know exactly why not.  Im assuming it's something to do with the Hydrogen atoms of the amide anion, though I could be wrong.  Enlighten me.


texts:
In general chemistry, we learn that the equilibrium constant, defined in terms of activities, for the reaction

$$\ce{aA + bB -> cD + dD}$$

is given by

$$K_\mathrm{eq} = \frac{(\ce{C})^c(\ce{D})^d}{(\ce{A})^a(\ce{B})^a} $$

But I can't find any explanation as to why stoichiometric coefficients should be exponentiated rather than appearing as coefficients in the equilibrium expression or something else.


texts: Why can’t lanthanum through lutetium and actinium through lawrencium all be in group 3?

texts:
In 2015, IUPAC established a task force to “deliver a recommendation in favor of the composition of group 3 of the periodic table.”  Not much about their decision-making process has been made known to the public.
It is noteworthy that the task force must select one of two compositions for group 3:

the elements Sc, Y, Lu and Lr, or
the elements Sc, Y, La and Ac.

This seems to call into question the conceptual validity of arrangements that depict La–Lu and Ac–Lr as falling under the umbrella of group 3 by leaving a gap, such as the one currently published on PubChem (as opposed to arrangements that insert the f-block between groups 3 and 4, such as the one currently on RSC.org).
If all the lanthanides, including lutetium, are so similar, and if all the actinides, including lawrencium, are so similar, why was a third option—“the elements Sc, Y, La through Lu, and Ac through Lr”—disqualified as a recommendation for the composition of group 3 by IUPAC?


texts: Trend in results for reproducibility of iron and phosphate

texts: Periodically in our lab, we have a reproducibility test for the various samples that we analyze. One such sample is boiler water. Two of the parameters that we test are phosphate in boiler water and iron in boiler water. Random error aside (shaking of sample, measurement bias, etc.), why are my iron results usually lower than the original and my phosphate is usually higher? Is there any chemical basis for these trends?


texts: In what we usually consider combustion your fuel and oxidizer are always neutral, but is it possible to have a similar "explosive" combustion process where both the fuel and oxidizer have been singly ionized? If so what might some potential fuels be, and where might more information on the topic be found? A google search doesn't turn up much (other than injecting a small amount of plasma to catalyze an otherwise non-ionized reaction.)


texts:
I know that complete combustion is a process where a fuel reacts with $\ce{O2}$ to become $\ce{CO2}$ and $\ce{H2O}$. But what is incomplete combustion?

According to the Internet, $\ce{CH4 + O2}$ and $\ce{C6H12O6 + O2}$ are examples of incomplete combustion. What makes them so?


texts:
Which is more acidic: p-xylene or 3-methoxytoluene?

$\ce{OCH3}$ shows -I and +M effect, and $\ce{CH3}$ shows +I effect. Since, the former shows some -I effect, it should be more acidic. But that's not the case. Any other explanation here?


texts: Can superoxide ion act as a ligand in a similar fashion as peroxide?

texts:
There is a question in my chemistry book:

  Find oxidation state of platinum ion in the complex $\ce{[Pt(O2)(en)2Br]+}$.

My books says that there is peroxide, but I want to ask why it is peroxide? Can it be superoxide?

My answer was that oxidation state of platinum is $+3$, but the answer in the book given is $+4$ with explanation that $\ce{O2}$ here is peroxide. How can I get to know from the formula that $\ce{O2}$ is peroxide and not superoxide?


texts: R,S Configuration of asymmetric carbon atom when group priority 3 and 4 are not on wedge bond?

texts: I am not blessed with the gift of spatial awareness. I understand how to determine the configuration when a group with priority 4 is on the hashed wedge or when the group with priority 4 is on the bold wedge and priority 3 is on the hashed wedge. However are there any rules I can follow for situations as shown in the image? The numbers show the priority.


texts: Why does C=O have a larger dipole moment than C-O?

texts:
Why does $\ce{C=O}$ have a larger dipole moment than $\ce{C-O}$?

According to me, dipole moment directly depends upon bond length and electronegativity difference. In $\ce{C=O}$ and $\ce{C-O}$, (I guess, please clear if I am wrong) the EN difference is same, and bond length of $\ce{C=O}$ is less than $\ce{C-O}$. So, $\ce{C=O}$ must have less dipole moment than $\ce{C-O}$ but it is not so. Why?


texts: Reason for protonation of amino group in amino acids at near neutral pH

texts:
What happens to the amino group when amino acid is added to a near neutral solution? How does it come about gaining an extra proton?
I understand what happen to the carboxyl group, since it is a strong acid it will dissociates quickly to donate a proton.


texts: How come Cyclopropenylhydroxide exists and not cyclopropenol?

texts:
I'm currently studying aromatic compounds via online recorded lectures, and my teacher brought up about cyclopropenol and cyclopropenylhydroxide while teaching carbocylic non benzenoid compounds. He said the latter exists while the former doesn't exist; and due to time restrictions they cut off the part where he explains the reason, out of the video.
So why doesn't it exist?


texts: Why is chloride oxidised instead of water in copper chloride electrolysis?

texts:
For the Electrolysis of Copper Chloride:

Cathode: $\ce{Cu^{2+} + 2e- <=> Cu}$
Anode: $\ce{2Cl <=> Cl2 + 2e- }$

I am confused about the reaction taking place at the anode. Wouldn't $\ce{H2O}$ rather undergo oxidation since it has an increased reducing ability? eg. It is above $\ce{2Cl-}$ on the Table of Standard Reduction Potentials.

Am I missing something? Or do all halogens discharge more readily than water?


texts: Why are arenes with conjoined benzene rings drawn as they are?

texts:
Whilst we are taught to represent benzene as below (A) due to its delocalised electrons, however when two benzene rings share carbons (e.g. naphtalene) it seems to be more commonly represented in textbooks as two conjugated rings (B).  Whilst I realise that the result is the same, what is the advantage gained by drawing them like this rather than (C)?  Is it simply a matter of clarity?
A:

B:

C:

Whilst draing those in Marvin I wondered if it was as the delocalisation between the shared carbons isn't shown?  I.e. it looks like the electrons are delocalised across both rings separately rather than as one big ring?


texts: Why is a racemic mixture formed in the Diels-Alder cycloaddition? I note that for both endo and exo products, either enantiomer can be formed. Why is this so?