texts: Coordination numbers of ionic and intermetallic compunds

texts:
If $\ce{NaCl}$ crystallizes in an fcc lattice, its coordination number should be 12. Then why do we say that $\ce{NaCl}$ has a coordination number of 6?
Also, if $\ce{CsCl}$ crystallizes in a simple cubic lattice, why is it's coordination number 8 and not 6, as for other simple cubic lattices?


texts: Why use potassium iodide instead of copper iodide in Sandmeyer reaction?

texts:
The Sandmeyer reaction is an extremely useful reaction for the functionalization of aromatic rings through a diazonium intermediate. For conversion of a diazonium intermediate to the corresponding chloride, bromide, or cyanide, the copper(I) salt is used. Surprisingly (to me at least) for iodination, potassium iodide is the reagent of choice, as described in Maitland Jones's Organic Chemistry (and elsewhere I'm sure), but no rationale is given. SciFinder searches also show that potassium iodide is most frequently used.

Is there something special about copper(I) iodide that makes it unsuitable for use in the Sandmeyer reaction?


texts: Applying vacuum at the end of a flash chromatography column

texts:
I know that flash chromatography uses a positive or pushing pressure to achieve the   goal which is separation. Would the same goal be achieved if you had a vacuum on the other end instead of a pressure at the top, a vacuum on the bottom?

I have used this technique for ion exchange column with efficient and quick results and wonder if this can be achieved with flash chromatography.


texts: Why does white phosphorous exhibit chemiluminescence?

texts: My work - I only know that chemiluminescence means glowing in dark.


texts:
For Christmas I bought my children a "Magic Growing Christmas Tree Crystal Paper Tree Christmas Decoration Science Toy". It looks like this:

It came with a bag of liquid which you add to the tray at the bottom and then 'evaporates' up the tree.

Presumably the liquid has an ionic solution which then crystalises as the solution rises up the tree and the liquid evaporates.

From my limited knowledge of playing with growing crystals as a boy - the two ionic solutions that came to mind were:

table salt - sodium chloride - white crystals
sodium sulphate - blue crystals

The shape of the crystals was fine fingers - not like either of those solutions - which tend towards large crystals. In addition the colour came from the tint on the paper - so it must have been white originally.

My question is: What is the reaction involved in a childrens paper Christmas tree crystal growth?


texts: Is the equation dG = Vdp − SdT valid only for a reversible process? Can it be applied for an irreversible one too?

texts:
In the derivation, we write:

$$
\begin{align}
G &= H - TS &\quad&\to&\quad \mathrm dG &= \mathrm dH - T\,\mathrm dS - S\,\mathrm dT \\
H &= U + pV &\quad&\to&\quad \mathrm dH &= \mathrm dU + p\,\mathrm dV + V\,\mathrm dp \\
U &= Q + W &\quad&\to&\quad \mathrm dU &= \mathrm dQ - p\,\mathrm dV \\
  & & & & &= T\,\mathrm dS - p\,\mathrm dV
\end{align}
$$

So solving these gives

$$\mathrm dG = V\,\mathrm dp - S\,\mathrm dT$$

But what we actually write is

$$\mathrm dH = \mathrm dU + p_\mathrm{int}\,\mathrm dV + V\,\mathrm dp$$

And in

$$\mathrm dU = \mathrm dQ - p\,\mathrm dV = T\,\mathrm dS - p_\mathrm{ext}\,\mathrm dV$$

so on solving, it should be

$$\mathrm dH = T\,\mathrm dS - (p_\mathrm{ext} - p_\mathrm{int})\mathrm dV + V\,\mathrm dp$$

And only in reversible process, should it be valid to write

$$p_\mathrm{ext} - p_\mathrm{int} = 0$$

But my teacher argued that because this is a state function, it should be valid for all types of processes. I'm a bit confused about how his claim is valid. Can someone please explain what he means or even if he is correct or not?


texts: Is the reaction of anhydrous aluminium(III) chloride and anhydrous ethanol reversible?

texts:
I'm planning an experiment that I'll do in silico in the near future, and one of the steps involves the extraction of the $\ce{AlCl3 · C2H5OH}$ adduct without any water in it.

Can the ethanol be simply boiled off to obtain anhydrous aluminum chloride, or does it end up as, say, a mixture of ethyl chloride and aluminum hydroxide or something?


texts: Does tetramine copper dissolve cellulose?

texts: I saw a Youtube video which showed that cotton (cellulose) dissolves in deep blue solution of tetramine copper made by adding 20% ammonia in copper carbonate salt. I tried to replicate the process using $\ce{CuSO4}$ and copper chloride. None worked. Where have I gone wrong?


texts:
Can an identification experiment (using acetonitrile, isopropyl, and cyclohexane) using simple distillation and boiling point be improved by using a digital thermometer?

Can simple distillation be improved in other ways, other than a more accurate thermometer? That's all I've come up with.


texts: How to resolve Amine Blush problems of a Epoxy curing Agent without having to change the temperature and moisture of the air?

texts:
The formation of Carbamate as a result of the reaction between amine groups of curing agents and H2O/ CO2 leaves the surface of the cured epoxy with some blurry lines and dots. the typical solutions like reducing the moisture and heating the environment and making the curing agent faster will work the issue, but as the problem, at hand, we want to formulate a curing agent which can work in lower temperatures with higher moisture content (above 50% humidity) without altering any of the characteristics of the original Hardener. What type of material can resist moisture or can reduce the formation rate of carbamate ?
We are using "TETA" as the amine part of the formulation and using other amines at this point is not possible for the company.


texts: How much of Sodium dichloro-s-triazinetrione dihydrate should I use to replace bleach?

texts:
I am trying to determine how much sodium dichloro-s-triazinetrione dihydrate powder I should add to water to create a dilution that can be injected into my water supply to react with the Hydrogen Sulfide and remove it.

I have a system in my home that uses sodium hypochlorite (bleach) and water. There is a 30 gallon water barrel that we mix 1 gallon of bleach (5.25% Sodium hypochlorite) with 29 gallons of water. I believe that means the resulting mixture is 0.16666% Sodium hypochlorite. That is injected using a small pump into the water supply where it mixes in a tank and oxidizes the Hydrogen Sulfide.

I want to stop buying bottles of bleach which is expensive and contains additives other than sodium hypochlorite. I would like to switch to sodium dichloro-s-triazinetrione dihydrate which I already have an abundance of in the form of Spa Sanitizer. The Spa Sanitizer label indicates it is 99.99% pure sodium dichloro-s-triazinetrione dihydrate.

So how much of the sodium dichloro-s-triazinetrione dihydrate powder do I need to mix with 29 gallons of water to create a solution similar to the one created by the bleach? (0.16666% sodium hypochlorite)

Or, maybe what I should be asking is what is the amount of free chlorine in the 0.16666% sodium hypochlorite solution and how much sodium dichloro-s-triazinetrione dihydrate powder do I need to mix with 29 gallons of water to achieve the same amount of free chlorine? Since I believe the free chlorine in sodium hypochlorite and sodium dichloro-s-triazinetrione dihydrate are not actually the same.


texts: In which all substituents does Inductive effect overpower Mesomeric effect?

texts:
In most substituents, the mesomeric effect is considered stronger and more dominating than the inductive effect.
A notable exception are the halogens.

The reason behind this has been well-explained here.

I further had questions about the following:

Since its about the EN, would all other electronegative elements with lone pair show this anomaly?
Are there other substituents with this exceptional behavior?


texts: Why is vicinal diiodopropane unstable, leading to deiodination?

texts:
I came across this reaction where simple electrophilic addition mechanism will result in a vic-diiodide.
$$\ce{H2C=CH-CH2-I ->[HI, excess][CCl4]}$$
But the solution says that vicinal iodine groups are unstable and the following reaction occurs:
$$\ce{CH3-\underset{(unstable)}{\underset{\underset{\huge I}{|}}{C}H-\underset{\underset{\huge I}{|}}{C}H2} ->[][$-$I2] CH3-CH=CH2}$$
I am unable to figure out how the dihaloalkane is unstable. It might be due to steric reasons, but still the two iodine can arrange in a way that reduces the repulsions.
But even if it is unstable, how did $\ce{I2}$ leave the haloalkane to yield an alkene? This dehalogenation does happen when a metal is used though (Zn dust, Mg in acetone, I guess) but what would be the mechanism here?


texts: How and why does this Cu change into C (graphite)?

texts:
Source: gutefrage.net

At the right side of the graphic, the Cu changes while discharging into C as graphite. How and why does this happen?

I thought it happens because of the dissolving of the Cu when the electrons stream from the Cu to the Al.


texts: If Mendelev hadn't put the periodic table in its current order, would it still have been made popular?

texts:
What I mean is, does the current model make the most sense? The QWERTY keyboard was made popular because someone won a typing contest with it, and is widely used today, even though other keyboard designs might have made more sense. Is our current periodic table also just popular for an arbitrary reason, or is it actually the best design possible? If things had played out differently, is there a high chance we would use another table?
Thank u


texts: Differences in using molten NaCl compared to aq. NaCl in a galvanic cell having copper anode and cathode

texts:
Since we know that copper anode will release $\ce{Cu^2+}$ ion, so I was wondering whether the cathode will thicken as copper has a lower position on the electrochemical series.
Based on my research, I found that some said that cathode will only thicken if the solution is stirred, some said that hydrogen gas will form.
Hence, are there any difference if electrolyte used is in a molten state compared to in an aqueous state?


texts: What is the chemical reaction behind ginger milk curd?

texts: Pouring hot milk into ginger juice solidifies the milk. All I know is that ginger juice contains Zingibain that could break down milk proteins into smaller polypeptides. I'm confused as though why is this sufficient to solidify the milk?


texts: Why does the Lewis definition of acids specify a PAIR of electrons and not a single electron?

texts:
The Lewis definition of an acid is: "a compound or ionic species which can accept an electron pair from a donor compound."

Why does it specify a pair of electrons and not just a single electron?

I initially thought maybe covalent bonds require a pair of electrons but it says that is not the case here : https://en.wikipedia.org/wiki/Covalent_bond#One-_and_three-electron_bonds

__

For reference:

Question from textbook :
Which of the following species can act as a Lewis acid?

$\ce{NH3}$
$\ce{F-}$
$\ce{H2 O}$
$\ce{NH4+}$
$\ce{BF3}$   (answer)

I thought the answer was $\ce{NH4+}$  as it could accept an electron, but the Lewis definition specifies accepting a pair of electrons.

Thanks.


texts: How to calculate the amount of substance of nitrogen that dissolves in water?

texts:
The Henry's law constant for the solubility of $\ce{N2}$ gas in water at $298~\mathrm{K}$ is $10^5~\mathrm{atm}$. The mole fraction of $\ce{N2}$ in air is $0.8$. The amount of substance of $\ce{N2}$ for air dissolved in 10 moles of water at $298~\mathrm{K}$ and $5~\mathrm{atm}$ pressure is ___.

I think the mole fraction of nitrogen will be calculated using the formula $$x(\ce{N2})=P/K_h.$$ But the answer is wrong.
In the solution for the question, the mole fraction $x(\ce{N2})$ is multiplied further by $0.8$ which seems to the mole fraction of nitrogen in air.


texts:
This is an old question that our textbook tried to answer but worsened the situation.

Many things are soluble in water. So many, that studying solutions will always require studying aqueous ones. It is true that many non-polars like waxes are not very soluble in water, yet I have never run into a solvent as "good" as water.

But how were we answered when we asked that "why is water a good solvent"? They said since water is polar so the attraction between for example $\ce{O}$ and the positive ions is so much blah blah blah!

So either there are "great" solvents like water out there or there are other things about water that make it the master solvent that are beyond me.

Is there a solvent as "versatile" as water?
Can this kind of solvent be non-polar?
If the answer to the questions above is no, what is special about water?


texts: How to determine an unknown metal based on the reaction products with oxygen and fluorine?

texts:
The following question is, as it will probably be obvious, a homework question, however I have absolutely no idea how to progress with it beyond what I have already done. This is the question:

  $\pu{10 g}$ of an unknown metal reacts with oxygen to produce $\pu{16.58 g}$ of the metal oxide. $\pu{10 g}$ of the same metal reacts with fluorine to produce $\pu{25.63 g}$ of the metal fluoride. The valency of the metal is identical in the metal oxide and fluoride produced. Identify the metal after finding the mass of one mole.

My attempt:
\begin{align}
  m(\ce{O2}) &= \pu{ 6.58 g} & \implies&& n(\ce{O2}) &= \pu{0.206 mol}\\
  m(\ce{F2}) &= \pu{15.63 g} & \implies&& n(\ce{F2}) &= \pu{0.411 mol}
\end{align}

I also made the equations, where X was the unknown metal:
\begin{align}
  \ce{X + y/2 O2 &-> XO_y}\\
  \ce{X + z/2 F2 &-> XF_z}\\
\end{align}

Any help with where to go next would be massively appreciated.


texts: How is the oxidation number related to the group number?

texts:
If an element $\ce{X}$ forms the highest oxide of the formula $\ce{XO3}$, then it belongs to group:
  A) 14
  B) 15
  C) 16
  D) 17

How is an oxidation number of an element related to its group?

I tried comparing $\ce{X}$ with $\ce{N}$-, $\ce{S}$-, $\ce{As}$-compounds, but all 3 come in the form $\ce{XO3}$ ($\ce{NO3}$, $\ce{SO3}$, $\ce{AsO3}$), so I can't guess the group number.


texts: How do we know that there are different types of orbitals? For example, what evidence is there for the existence of $\mathrm{p}$ orbitals instead of there being multiple $\mathrm{s}$ orbitals (for example, why isn't the electronic configuration of sodium $\mathrm{1s^1, 2s^2, 2s^2, 2s^2, 2s^2, 3s^2}$ instead of $\mathrm{1s^2 2s^2 2p^6 3p^1}$)?


texts: How to calculate the variation of enthalpy in a reaction that does not occur in standard conditions?

texts:
Standard enthalpy of formation is a value that represents the enthalpy variation in the formation of compounds with the purpose of using this values to know the enthalpy of a reaction where these compounds participate.

Those values are referred to the formation of said compounts at 273 K and 1 atm (known as standard conditions).

My question is:

Does the value change, for distinct pressures or temperatures? If yes, how?

Why am I asking this?

Let's suppose I have a reaction that goes like this:

$A + B \rightarrow C$

At 1 atm and 273 K (standard conditions).

I can say that in this reaction $\Delta H = Hf^0(C) - Hf^0(A) - Hf^0(B)$

Where $Hf^0$ means standard enthalpy of formation.

Because the reaction happens at 1 atm and 273 K.

But, what if the reaction happens at 3 atm and 350 K?

I asked my University teacher and he said: "You don't need that because we will always be working at 1 atm and 273 K".

What tool do I have to know the variation of enthalpy in this case?

A small extra confusion is the fact that in some examples I see standard conditions being 1 atm and 273 K, and some other times it's at 298 K.


texts: Dihedral angle of gaseous and crystalline HOOH

texts:
Why does hydrogen peroxide exhibit a dihedral angle of $111.5^\circ$ in the gaseous state? And a dihedral angle of $90.2^\circ$ in the crystalline phase?

I know that in general, there is likely to be more hydrogen bonding in the crystalline phase than in the vapor phase.
But what's up with 1) the bond angles themselves in the first place and 2) the bond angle expansion in the gas phase? How can one rationalize them?
I know that there exist lone pairs on the oxygens and lone-pair/lone-pair repulsion should probably be minimized, but what it is about these conformers that minimizes energy? I'm guessing that we'd also want to minimize eclipsed and gauche interactions ... Newman projection time?
It seems that there is only one Newman projection possible for $\ce{HOOH}$; i.e. we'll have the inevitable lone-pair/lone-pair interaction, and the lone-pair/hydrogen interaction. I guess all we can do is minimize these interactions; i.e. the energy-minimized conformer is probably not the one with them all eclipsed. However, why does it seem that the energy-minimized conformer for vapor $\ce{HOOH}$ is one that puts the lone-pairs so close to each other in terms of dihedral angles?


texts:
As far as I know, paramagnetism in normal substance arises due to unpaired electrons. I believe that the valence electrons of group 2 elements (Be, Mg, Ca, Sr, Ba) are paired.

But, here in the list of given compounds, all of the group 2 elements (except Be) have positive susceptibility, and it is specified in the same document that positive susceptibility implies paramagnetism.

My question:
How can these elements show paramagnetic behaviour?


texts: How does spin flipping of triplet carbenes occur?

texts:
Below is presented a page from Clayden Organic Chemistry 2ed.

How and why does the spin flipping during the collision with solvent molecules actually occur?


texts: What is the link between the classical and quantum definition of the symmetry number?

texts:
From what I understand, the symmetry number for a molecule can be defined in 2 ways:
1. The quantum mechanical symmetry number corrects for overcounting the number of possible rotational states of a rotating molecule. Here's a source using this method.
2. The classical symmetry number corrects for including physical orientations of that molecule that appear the same because of its symmetrical physical structure. Here's a source using this method (a PDF file)
This source claims at the end of page 3, that the classical view is roughly based on the quantum view. I have a very hard time to grasp that.
How does the physical structure of a molecule have anything to do with nuclear spins being integer or half-integers, whether the total wavefunction needs to be symmetrical or antisymmetrical, and thus determining which rotational quantum states are allowed for a molecule?


texts: I recently took a raman spectrum for a sample of graphene-pla. The result had the characteristic G and D bands associated with Graphene, but not the 2D. But there is a broad peak at around 3100, which goes up from 2600. The sample was treated before being characterized. Does anyone know why this might have happened?


texts: How can I increase the signal intensity and precision?

texts: How can I increase the signal intensity and precision when use HPLC or LC-MS/MS ? How Also prevent Contamination and Carryover during Analysis


texts: Setting to basis set for electron transfer in type II CdS/TiO2 heterostructre for PYXAID package

texts:
I am studying electron injection from $\ce{CdS}$ into $\ce{TiO2}$ using NAMD approach. Now I'm using pyxaid package.
Would be possible  someone kindly help me with construction of basis set for this process?
30 bands selected for Hamiltonian construction and from this selected band set number and active space of [6-13] has been made. 7 is the valence band and 8 to 13 are conduction states.
For initial electronic state I selected -11,-12,-13 (one of which could be $\ce{CdS}$'s lumo) as I found from some preliminary decoherence rate calculations (12 decoherence more rapidly than 9-12).

params["active_space"] = [6,7,8,9,10,11,12,13]

# Generate basis states
params["states"] = []
params["states"].append(["ES1",[6,-6,7,-8]])
params["states"].append(["ES2",[6,-6,7,-9]])
params["states"].append(["ES2",[6,-6,7,-10]])
params["states"].append(["ES2",[6,-6,7,-11]])
params["states"].append(["ES2",[6,-6,7,-12]])
params["states"].append(["ES2",[6,-6,7,-13]])

# Initial conditions
nmicrost = len(params["states"])
ic = []
i = 0
while i<100:
    j = 3      # started from -11,-12,-13 one of which I believe belongs to CdS (donor semiconductor)
    while j<nmicrost:
        ic.append([2*i,j])
        j = j + 1
    i = i + 1

params["iconds"] = ic


texts: Osmotic pressure of a solution of a protein?

texts:
A small protein molecule, code-named "sloth", has a MM of $\mathrm{1.50 x 10^4}$ g/mol. What is the osmotic pressure exerted at $\mathrm{24.0^oC}$ by 25.0 mL of an aqueous solution that contains $\mathrm{3.75 x 10^{10}}$ nanograms of "sloth"? R = 0.08206 (atm L)/(mol K).

The equation my professor gave me is: $\mathrm{O.P. = T*R*M}$. So I did:

$\mathrm{O.P. = (24.0 + 273) K * 0.08206 (atm*L)/(mol*K) * ([(3.75 x 10^{10})x 10^{-9} g] / 1.50 x 10^4 g/mol) / 0.025 L}$

I keep on trying and I get 2.44 atm, but my professor marked the correct answer as $\mathrm{2.44 x 10^{-3}}$ atm. I think he may have divided the moles of sloth by 25 instead of .025 L, which would make his answer $10^3$ smaller than mine. Did I do something wrong?


texts: Can a reaction of the form A + B → AB ever be endothermic?

texts:
I understand that forming a bond between $\ce{A}$ and $\ce{B}$ is an exothermic process, with negative enthalpy, but won't there be energy required to get $\ce{A}$ and $\ce{B}$ close enough together for the bond to form?  So we would get an energy hill with activation energy on one side and heat of formation on the other side.

Is it ever possible in a chemical reaction to have more energy required to get the reactants $\ce{A}$ and $\ce{B}$ close enough together than the energy released in forming the bond?  In terms of atoms I am thinking that the repulsion between two atoms may reach a peak at some distance greater than the bond length, so we might get an energy hill diagram where:

What about a situation like breaking and forming bonds on elemental crystals like graphite and diamond?  If graphite pieces $\ce{(A)}$ are sloughed off of a large piece of graphite $\ce{(B)}$ this obviously requires energy to break the bonds, but the graphite flakes don't spontaneously re-bond to the large piece upon light contact.
Likewise, a fractured diamond does not re-bond on contact. Also, in formation of a diamond, why is there a need for a continual input of heat?  If the energy of formation is greater than the energy needed to activate the reaction, then wouldn't the released heat of formation cause other diamond bonds to form without more input of energy.  This indicates to me that some energy is required to begin the process of combining $\ce{A + B}$ to form $\ce{AB}$, even if the actual bond formation is exothermic - that there is a two sided energy hill in reactions of $\ce{A + B -> AB}$, though the activation portion may be smaller than the formation portion.
What about an analogous $\ce{A + B -> AB}$ nuclear fusion reaction with heavy species above iron?  Clearly in this case there is a large input of energy needed to fuse elements above iron, and a small release as the nucleons reach a distance that allows the strong nuclear force to dominate.  In this case the energy hill has a greater required activation energy than an energy of formation.  How is this fundamentally different from chemical bonds?
I understand that a critical component is that nuclear attraction becomes stronger than electrostatic repulsion at a critical distance, but might there be some instances of chemical reactions where $\ce{A}$ and $\ce{B}$ have to pass through a less stable conformation to get to the more stable bonded state?

So there are three possible answers:

$\ce{A + B -> AB}$ reactions can be described energetically solely by the heat of formation of the bonds between $\ce{AB}$.
$\ce{A + B -> AB}$ can be energetically described by an energy hill, but the heat of formation will always exceed the activation energy, or the energy required to move $\ce{A}$ and $\ce{B}$ through any intermediate states that are less stable than $\ce{A + B}$ (far apart).
$\ce{A + B -> AB}$ can sometimes be exothermic where the energy required to move $\ce{A}$ and $\ce{B}$ into an arrangement that will allow bonding can exceed the heat of formation of the bond between them.


texts:
An unknown gas at $\mathrm{63.1\ ^\circ C}$ and $\mathrm{1.05\ atm}$ has a molar mass of $\mathrm{16.04\ g/mol}$.
  What is the density of the gas?

I know I need to use the $pV=nRT$ equation but it gives me g/mol and not moles. I'm not really sure what to do here.

$$1.05\ V = n\ 0.08206 \cdot (63.1+273.15)$$

Ok that's as far as I got. I have no idea how would I even go about converting g/mol back to moles so I can solve for V, and after that I would also need to figure out a way to find grams so I can divide g/v to get the density.


texts: Amount of Cl- needed to precipitate AgCl given Ksp and [Ag+]

texts:
Why is $0.25 \ \mathrm{mL}$ the correct answer in this problem?

I used the Ksp to find the molarity of Chlorine to be $3.47 \times 10^{-2} \ \mathrm{M}$.

Then I used the formula

$$\text{Molarity}_{\text{initial}} \times \text{Volume}_{\text{initial}} = \text{Molarity}_{\text{final}} \times \text{Volume}_{\text{final}}$$

to find the volume of Chlorine, which turned out to be $0.21 \ \mathrm{mL}$  for me. However, my answer does not match the correct answer.

What am I doing wrong?


texts: Is it possible for already charged metal ions to form a metallic bond?

texts:
I would like to know if it is possible for already charged metal ions to become part of a metallic bond.
I was thinking of a possible metallic bond formation with other already charged metal ions or a metallic bond formation between elemental uncharged metal atoms and already charged charged metal ions. By formation a mean the moment before the metallic bond has formed because my understanding is that in a metallic bond there are only charged metal ions and no elemental uncharged metal atoms.
If one of the two scenarios or even both could occur I would assume that the already charged metal ions would form or join a metallic bond by either giving up or donating additional electrons to the so called sea of electrons of a metallic bond or the already charged metal ions would form or join the metallic bond by not giving up additional electrons.
It would be very helpful if someone could provide a link for citation about whether or not charged metal ions can become part of metallic bond since I could not find anything explicitly ruling out that possibility.


texts: Can water be liquefied or solidified just by adjusting the temperature, regardless of the pressure?

texts:
technically the line between liquid and solid phase would go a long way before hitting the y-axis, but the point is it will eventually.

So the question remains, can any liquids, including water (with its unique phase diagram) be liquefied regardless of the pressure?


texts:
when dealing with waste water and the total values of P, N, C are given in ppm units, what molecular weight is used for converting from ppm to molar?

for Example- what will be 12 ppm of P(T) in Molar unit?


texts: Lithium has two electrons in $\mathrm{1s}$, filling the first energy level; and one valence electron in $\mathrm{2s}$. Could two $\ce{Li}$ atoms form a bond to create $\ce{Li2}$; like $\ce{O2}$ or $\ce{C2}$?


texts: What is the definition of a "Simple enzyme" exactly? Is it an enzyme that does not require a co-factor?

texts:
I'm having a hard time making a distinction between simple and complex enzymes. the definitions I've found so far all say this:

  Simple enzymes are enzymes that are only made out of protein, and complex enzymes are ones that, in addition to the protein portion, have a non-protein portion as well, which is called a co-enzyme/prosthetic group (I've seen both terms being used)

Does this mean that any protein that utilizes a co-factor, even if that co-factor is simply a co-enzyme or an activating metal, i.e., not an actual part of the enzyme's structure, is considered a complex enzyme? Or are the two terms restricted to the structure of the enzyme (i.e., whether they have prosthetic groups, be they organic or inorganic, or not)?


texts: Basic and nucleophilic character of NaOH (aq)

texts: Sodium Hydroxide (aq) is very effective in plucking off an acidic hydrogen. How effective will it be in substituting chlorine of an alkyl hallide (let us assume that the alkyl hallide is primary) and why ?


texts: What is the scientific term to describe the operation of a bong?

texts:
What is the scientific term for the separation of dust particles from air by suction through a specialized flask in a way similar to the operation of a bong?

The thing that led me to this was a vacuum cleaner that uses water to separate dust and other particles from the air by vacuuming the air through a water bowl, and the only thing that is similar to that operation is the bong. It is like sparging, but the gas coming in will contain particles and those particles are the ones that remain in the liquid, and that same gas is the one coming out, filtered to some degree from those unwanted particles.


texts: Why can't you use m-CPBA to synthesise isophorone oxide from isophorone?

texts:
Apparently you must use sodium hydroxide and hydrogen peroxide because using m-CPBA gives an undesired product

Why doesn't m-CPBA work and what does it do instead? Why does sodium hydroxide and hydrogen peroxide work?


texts: How to calculate the volume of a 0.1 M NaOH(aq) solution necessary to make a 0.5 M EDTA solution with pH = 8?

texts:
I was told that EDTA dissolves at a pH of $8$. Therefore I need to use a base to increase the pH to $8$ is what I understand. How exactly would I go about this?

In my head I if I wanted $1~\mathrm{L}$ of $0.5~\mathrm{M}$ EDTA I would take $186.12~\mathrm{g}$ of the EDTA, since its molar mass is $M = 372.24~\mathrm{g\,mol^{-1}}$.

Then I would add $800~\mathrm{mL}$ of distilled $\ce{H2O}$ to dissolve it, but since it wont be at $\ce{pH}=8$, it wont dissolve.

So I assumed I would just add it drop wise until it dissolved while spinning? I lack access to a burrette and only have a crappy pH meter to check pH.

One I observe the EDTA dissolved I simply add up to $1000~\mathrm{mL}$?

I just wish I had a way to figure out how much $\ce{NaOH}$ I needed to add to dissolve the EDTA so I wouldn't have to do it drop wise.


texts: What will be the name of CH2=CH-O-CO-CH3?

texts:
We have this question in the textbook but there is no answer given and I have no idea how to name this compound.

Edit: I tried naming the compound.
Correct me if I am wrong here
1-Methylpropenoate


texts: Why cobalt reacts favorably with nitrogen?

texts:
I used also iron, nickel, zinc, copper. However, cobalt gives the easiest and straight forward yield of nitrides (XPS and SAED verified).
It is so easy to get cobalt nitride that I don't even have to use high purity nitrogen as I need with $\ce{Fe},$ $\ce{Ni},$ $\ce{Zn},$ $\ce{Cu}.$

Is there any reason for that? Is it because of back-bonding?


texts: Why do elements change their colour in reactions?

texts:
We are almost common with the reaction:
$\mathrm {CuSO_4+Fe = FeSO_4+Cu }$. In this reaction initially Copper sulphate is bluish in colour, which gradually changes to pale green. I want to know, why these elements have so and so specific colour, OR what determines the colour of these elements?  Further, why there is such specific change of colour as in copper sulphate observed?


texts: Concise description of primary organic reaction types mechanisms

texts:
Long story short, I'm mostly doing calculations in the past 5 years of my scientific carrier and every year I get less and less confident in my knowledge of organic chemistry which besides was never perfect. Yeah, I still remember pretty well some trivial things like nomenclature, classes of compounds, etc., and I'm pretty comfortable with MO theory, hybridization, etc., but all this are, so to speak, just the foundations of the organic chemistry. What I'm really bad at are the applications, primarily, the reaction mechanisms.

Many times reading a paper on computational studies of a reaction mechanism I caught myself not being able to (relatively quickly) grasp the main idea. I spent a fair amount of time just to recall the very basics of, say, the $S_N2$ reaction. Back many years ago I knew this things. Maybe I knew them not so perfectly and systematically, but even this knowledge of organic chemistry had evaporated almost completely from my head.

So I'm looking for a good resource to refresh and improve my knowledge of organic chemistry primarily (read: almost exclusively) regarding the most common reaction types and their mechanisms. A resource is counted as a good one if:

It is goes straight to the point (reaction mechanism) without discussing the basics of organic chemistry I mentioned, rather assuming that the reader knows them.
It is (relatively) concise and concentrated on the basics. In other words, I have neither time nor interest to read 2000 pages long Advanced Organic Chemistry book with all the details, exceptions, dirty laundries, etc. Just the basics.
On the other hand the basics has to be discussed in sufficient details, i.e. I would not be satisfied with the relevant Wikipedia (or similar) pages.
It is trustworthy. I mean, well established authoritative reference.

I admit I might ask for to much, but who knows, maybe there is something I'm looking for out there.

P.S. The type of a resource does not matter: textbook, lecture notes, MOOC video course, whatever.


texts: What would be the physical interpretation of the equation dG = Vdp − SdT?

texts:
I was trying to understand the derivation of the formula $G=G^\circ+RT\ln (p/p^\circ)$ starting with the following relationships:
$$
\begin{align}
\mathrm dU&=T\,\mathrm dS-p\,\mathrm dV\tag{1}\\
\mathrm dH&=\mathrm dU+p\,\mathrm dV+V\,\mathrm dp=T\,\mathrm dS+V\,\mathrm dp\tag{2}\\
\mathrm dG&=\mathrm dH-T\,\mathrm dS-S\,\mathrm dT=V\,\mathrm dp-S\,\mathrm dT\tag{3}
\end{align}
$$
Under isothermal condition $\mathrm dG=V\,\mathrm dp$ $(\mathrm dT=0)$. Therefore, the change in $G$ from the standard state is given by:
$$
\begin{align}
\int\mathrm dG&=\int V\,\mathrm dp=\int\frac{nRT}p\,\mathrm dp\tag{4}\\
G-G^\circ&=\ln p-\ln p^\circ\tag{5}\\
G&=G^\circ+\ln\frac p{p^\circ}\tag{6}
\end{align}
$$
But I'm confused about the equation $\mathrm dG=V\,\mathrm dp-S\,\mathrm dT$. What does this physically mean?
I'm assuming $V\,\mathrm dp$ is some form of work done by the system, but that suggests $G$ of the system increases while it loses energy doing the work. I also have the same problem for $\mathrm dH=T\,\mathrm dS+V\,\mathrm dp.$ Can someone please explain what they really mean?


texts: Synthetic ferritin models and μ notation

texts:
This is the question verbatim:

  Details of two synthetic models of ferritin are presented below:

  System 1

  $$\begin{multline}\ce{Fe(OAc)2 + LiOMe ->T[in presence of $\ce{O2}$][in MeOH]\\
 Fe12(OAc)3(\mu-OAc)3(MeOH)4(\mu-OMe)8(\mu_3-OMe)10(\mu_6-O)2}\end{multline}$$

  System 2

  $$\begin{multline}\ce{Fe(O3SCF3)2 + L ->T[in MeOH]\\ [Fe6(OMe)4(\mu-OMe)8(\mu_4-O)2L2][O3SCF3]2}\quad (\ce{L~=~N(CH2CH2NH2)3})\end{multline}$$

  How valid are each of these systems as a model of ferritin? Consider
  both structural and functional features.

I have no idea how to start with this. I wasn't taught what the $\mu$ notation means nor about the structures of ferritin models. I'm guessing $\mu$ denotes a bridging ligand?

I know that oxygen binds very well to Fe, hence why it needs to be carefully controlled around it. The chelating nature of L can't be ignored.

Is the symmetry of the structures important? I know that natural ferritin has 3 and 4-fold symmetry.


texts: Rubbing alcohol gets warm after diluting with water

texts:
I've just diluted a 95% rubbing alcohol bottle with water to bring it down to 70%. However, the bottle got noticeably warmer after I did so. I've searched online and I couldn't find any exothermic reaction that happens when alcohol is mixed with water. I did use mineral water by mistake to do so, so my best guess is that alcohol reacted with... one of the salts in the water... maybe?! (I have no idea)

Why did this happen?


texts:
Let's say we have a stable solution of
$\mathrm{A}_{\left(\mathrm{aq}\right)}^{2+}$
and $\mathrm{C}_{\left(\mathrm{aq}\right)}^{+}$
, with their respective counter-ions.

The associated redox reactions are:

$\mathrm{A}_{\left(\mathrm{aq}\right)}^{2+}+\mathrm{e}^{-}\rightleftharpoons\mathrm{A}_{\left(\mathrm{aq}\right)}^{+}\qquad\mathcal{E}_{\mathrm{A}_{\left(\mathrm{aq}\right)}^{2+}/\mathrm{A}_{\left(\mathrm{aq}\right)}^{+}}^{\circ}$

$\mathrm{C}_{\left(\mathrm{aq}\right)}^{2+}+\mathrm{e}^{-}\rightleftharpoons\mathrm{C}_{\left(\mathrm{aq}\right)}^{+}\qquad\mathcal{E}_{\mathrm{C}_{\left(\mathrm{aq}\right)}^{2+}/\mathrm{C}_{\left(\mathrm{aq}\right)}^{+}}^{\circ}$

where $\mathcal{E}_{\mathrm{A}_{\left(\mathrm{aq}\right)}^{2+}/\mathrm{A}_{\left(\mathrm{aq}\right)}^{+}}^{\circ}<\mathcal{E}_{\mathrm{C}_{\left(\mathrm{aq}\right)}^{2+}/\mathrm{C}_{\left(\mathrm{aq}\right)}^{+}}^{\circ}$
, since no reaction between $\mathrm{A}_{\left(\mathrm{aq}\right)}^{2+}$
and $\mathrm{C}_{\left(\mathrm{aq}\right)}^{+}$
is occurring.

The questions are:

Provided that neither $\mathrm{A}_{\left(\mathrm{aq}\right)}^{+}$
nor $\mathrm{C}_{\left(\mathrm{aq}\right)}^{2+}$
are present in the solution, how can we determine, form the Nernst equation, the $\mathcal{E}$ needed to start the electrolysis process
$\mathrm{A}_{\left(\mathrm{aq}\right)}^{2+}+\mathrm{C}_{\left(\mathrm{aq}\right)}^{+}\rightleftharpoons\mathrm{A}_{\left(\mathrm{aq}\right)}^{ +}+\mathrm{C}_{\left(\mathrm{aq}\right)}^{2+}$?
In other words, how can the Nernst equation deal with activities that are equal to zero?

Thanks in advance!


texts: How would the relative rate of reduction of carboxylic acid be if the catalyst used is LiAlH3D?

texts: How would the relative rate of reduction of carboxylic acid be if the catalyst used is LiAlH3D , LiAlH2D2 , LiAlHD3 , LiAlD4 just thought about it while revising the reaction mechanism of carboxylic acid reduction .


texts:
I was presented with the following problem and I am finding it difficult to present the half equations for the answers.

I managed to produce the half-equation for the Iodine redox.

$\ce{2I- -> I2 + e-}$

I then proceeded to the $\ce{CrO4^{2-}}$ equation.

$\ce{CrO4^{2-} + 3e- -> Cr3+}$

This is because the oxidation number of the Cr in $\ce{CrO4^{2-}}$ is $+6$ and it is reduced to $+3$

However, the answer is given as:

$\ce{CrO4^{2-} + 4H2O + 3e- → Cr3+ + 8OH-}$

I am struggling to get from the equation I made to the one presented in the answer for the $\ce{CrO4^{2-}}$ redox.

Can someone explain why there are $\ce{4H2O}$ on the left hand side and $\ce{8OH-}$ on the left hand side of the equation?

Please help!
Many thanks.


texts:
What is the meaning of $\ce{(en)}$ on this two coordination compounds:

$\ce{[Co(en)_2(NO_2)_2]Cl}$

$\ce{[Cd(en)_2(CN)_2]}$

Is it a type of compound? If yes, what is the meaning?


texts: Is equilibrium potential for K+ always ~-90 mV?

texts: Equilibrium potential is the difference in charge relative to the inside of the cell. -90 mV means that the inside of a cell is more negative than the outside. However when you talk about equilibrium potentials, I thought you only consider an individual ion like potassium? Potassium usually has 150 nM inside the cell and 5 nM out. If you allow potassium to freely pass through the membrane, wouldn't it eventually balance out so that the net charge on both sides is 0 (concentration would also be equal)? So why do people say that the equilibrium potential for K+ is -90?


texts: How to predict precipitate upon evaporation from calcium ions and either chloride, carbonate, or nitrate counterions?

texts:
An aqueous solution containing $\ce{Ca^2+}$, $\ce{Cl^-}$, $\ce{CO3^2-}$, and $\ce{NO3^-}$ is allowed to evaporate. Which compound will precipitate first?

The correct answer is $\ce{CaCO3}$. I had guessed that, and I know nitrates are soluble, so that wouldn't precipitate, but why the $\ce{CO3^2-}$ and not the $\ce{Cl-}$? Is it because of the equal and opposite charges between them? Does electronegativity play a role?


texts: Gaussian and Surface Reactions - Doable?

texts:
Independent from my general kinetics question here - Estimating Surface Reactions - Liquid, Turbulent Flow - I am only interested in responses regarding Gaussian in this question.

I would like to know if it is feasible to predict or model the influence of a surface (metal) on a reaction between two hydrocarbons (aromatic and aldehyde for example) in Gaussian.
If yes, how would I go about it? (Building a small metal grid and working with it is very computationally intensive - it is the only approach I can think off...)

(I have access to Gaussian at my university - however I do not have access to Linda, so no shared nodes.)


texts:
If electron makes transition from, in $H$ atom, $6\rightarrow 2$ (to Balmer), then $\bar{\nu}_{{H}_{6\rightarrow 2}}=x$ (let).

Also if electron makes transition from, in $He^{+}$ ion, so that $\bar{\nu}_{{He^{+}}_{a\rightarrow b}}=x$, gives me $a=12$ to $b=4$, by numerical caulations.

Now, what is observed is if I multiply $Z_{He^{+}}=2$ to transition of $H$ i.e. by $2\times\big({6\rightarrow 2}\big)=12\rightarrow 4$, gives me same result without any nasty calculation, why this works I don't know can you help me with this.

Thanks.


texts: Influence of neighboring fluorine and hydroxyl on carbocation

texts:
Which of the 2-fluorobutan-3-yl and butan-2-ol-3-yl carbocations will be more stable? I know that fluorine has a greater electron-withdrawing inductive effect, but what about the resonance effect of those?

$\hspace{35 mm}$


texts: Hund's rule for comparing term symbol energies in excited state

texts:
This question was asked in an exam:

The lowest energy electronic state for excited state carbon atom is,
a. $^1D_2$
b. $^3D_1$
c. $^3D_3$
d. $^3D_2$

Although we have been taught Hund's rule for determining the relative energies for various term symbols in the ground state, I haven't read anything about the rules for excited state anywhere. I couldn't not find it in the book I use i.e. Atkins, Physical Chemistry.
I am really confused about how to solve this. Also I don't think I actually understand the rationale behind Hund's rule.
Like we haven't been taught rigorously about it. Could someone explain it ?
Or maybe recommend a book or some source from where I can learn about quantum mechanics in greater depths?


texts:
Why are fluorides of transition metals unstable in low oxidation states?

I would think that since fluorine and oxygen are highly electronegative, it's obvious that they be stable at high oxidation states. However, $\ce{Cl}$  is also highly electronegative, but it does exist in low oxidation states with transition metals.

For example $\ce{CuCl}$ exists  but not $\ce{CuF}$ and  $\ce{TiCl2}$ exists but not $\ce{TiF_{2}}$. Why is it so?

  Fluorides of transition metals unstable in low oxidation states

This is the statement given in my high school chemistry text book but no explanation provided. I am interested to know the reason for it.


texts: At what frequency does a non-polar molecule acquire a dipole able to participate in London Dispersion forces?

texts:
London Dispersion forces are forces between non-polar non-ionic molecules that the random fluctuation of their electrons makes them temporarily dipoles.

What is the frequency that this occurs?
Every how many milliseconds does a molecule like this becomes a dipole?
Are there such numbers for some specific molecules out there?


texts:
I was looking through the thermodynamic data chart at the back of my textbook  and found that $\ce{S^{2-}_{(aq)}, F^{-}_{(aq)}, OH^{-}_{(aq)}}$ all have negative entropy values. But according to the Boltzmann equation, $S=k\ln W$, so if $S<0$, $W<1$. But since $W$ is the number of microstates, how can $W$ be less than 1?

I read in some other places than this is based on the entropy of $\ce{H^+_{(aq)}}$ being set to $0$, but why do we set this equal to $0$ and how does it follow Boltzmann's equation?


texts: How does a double displacement reaction work?

texts: When a double displacement reaction occurs with compound AB and CD, what determines that B and C are going to bond instead of A and C?


texts:
Strictly on theoretical basis, not based on experimental results.

I can very well be wrong, but I think that methanol should be
optically inactive because it has a plane of symmetry passing through it.
My teacher however insists that it is optically active as you can create two non-superimposable mirror images out of it.

Who is correct and why?


texts: How to use a modified Peng-Robinson equation to calculate a density?

texts:
I'm trying to use the Peng-Robinson-Stryjek-Vera 2 (PRSV2) Equation of State to calculate the density of a compound, in this example: methanol. At ambient temperature and pressure, shouldn't I be able to solve the cubic equation of state for the molar volume and calculate a density corresponding reasonably well to the density of the liquid given in the literature at those conditions of temperature and pressure? The values are considerably off, at least farther off than I would expect from such a well tested equation of state. For instance, for methanol, I obtain a density of 0.672 g/mL rather than the literature value of 0.791 g/mL. For acetonitrile, it's even worse: 0.480 g/mL rather than 0.786 g/mL. Does anyone have experience with such cubic equations of state? Are they simply not that accurate? Am I doing something wrong? I've checked my implementation numerous times for typos, but cannot find any.

This implementation in MATLAB comes from the following two papers:

Stryjek, R. and J. H. Vera, (1986). "PRSV: An Improved Peng-Robinson Equation of State for Pure Compounds and Mixtures", Can. J. Chem. Eng., 64, 323-333.

Stryjek, R. and J. H. Vera, (1986). "PRSV2: A Cubic Equation of State for Accurate Vapor-Liquid Equilibria Calculations", Can. J. Chem. Eng., 64, 820-826.

T = 298; % Temperature, in K
P = 1; % Pressure, in atm

% Values for methanol
M = 32.04; % Molar mass, in g mol^-1
T_c = 512.58; % Critical temperature, in K
P_c = 8095.79; % Critical pressure, in kPa
omega = 0.56533; % Acentric factor, from PRSV2
kappa1 = -0.16816; % From PRSV
kappa2 = -1.3400; % From PRSV2
kappa3 = 0.588; % From PRSV2

R = 8.3144598; % Ideal gas constant, in Pa m^3 mol^-1 K^-1
R = R*1000; % Ideal gas constant, in kPa cm^3 mol^-1 K^-1
T_R = T/T_c; % Reduced Temperature

kappa0 = 0.378893 + 1.4897153*omega - 0.17131848*omega^2 + ...
    0.0196544*omega^3;

kappa = kappa0 + (kappa1 + kappa2*(kappa3 - T_R)*(1 - (T_R)^0.5))*...
    (1 + (T_R)^0.5)*(0.7 - T_R);

alpha = (1 + kappa*(1 - (T_R)^0.5))^2;

a = (0.457235 * R^2 * (T_c)^2 / P_c)*alpha;
b = 0.077796*R*(T_c)/(P_c);

P = P*101.325; % Pressure, in kPa

% Using the PRSV EOS cubic expansion for molar volume
C3 = 1;
C2 = b - R*T/P;
C1 = a/P - 2*R*T*b/P - 3*b^2;
C0 = (b^2 + R*T*b/P - a/P)*b;

cubic  = [C3 C2 C1 C0];
v = roots(cubic); % Molar volumes, in cm^3 mol^-1

rho1 = M/v(1) % Density, in g cm^-3
rho2 = M/v(2) % Density, in g cm^-3
rho3 = M/v(3) % Density, in g cm^-3


texts: Why is the stoichiometric coefficient in the denominator in the rate expression?

texts:
For the reaction:  $$\ce{2A + B → C}$$

The rate expression is given as:

$$\ce{-1/2 * Δ [A]/Δt}$$  = $$\ce{-1 * Δ [B]/Δt}$$ = $$\ce{Δ [C]/Δt}$$

I can't get my head around why it is $$\ce{-1/2 * Δ [A]/Δt}$$  and not $$\ce{-2 * Δ [A]/Δt}$$

If A is consumed at twice the rate that B is consumed, why is the rate for A half (and not double) the rate for B?

The only answer I could find on the internet is "To show a standard rate of reaction in which the rates with respect to all substances are equal, the rate for each substance should be divided by its stoichiometric coefficient." Source: http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Kinetics/Rate_Laws/The_Rate_Law

But this doesn't make much sense to me. Why does the rate with respect to all substances have to be equal when one substance (A) is used up twice as fast as another substance (B)?


texts: Maximum required order for the Boys function

texts:
I am planning to pretabulate a lookup table in order to evaluate the Boys function. We can expand the Boys function as:

$$F_n (x_t + \Delta x) = \sum _{k=0}^\infty \frac{F_{n+k}(x_t)(-\Delta x)^{k}}{k!} \hspace{16pt} \tag{9.8.12}$$

We can then use downward recursion (upward is numerically unstable) in order to evaluate the function for any value of $n$ (order):

$$F_n (x) = \frac{2xF_{n+1}(x)+\exp(-x)}{2n+1} \tag{9.8.14}$$

I would like somebody to explain how one chooses which value of $n$ the lookup table will take? My working/logic so far as:

The Hermite integral has the following recursion (McMurchie-Davidson scheme, $x$ direction):

$$R^{n}_{t+1,u,v} = tR^{n+1}_{t-1,u,v} + X_\mathrm{PC}R^{n+1}_{t,u,v} \tag{9.9.18}$$

$\hspace{16pt}$ with:

$$\hspace{16pt} R^{n}_{0,0,0}=(-2p)^{n} F_{n}(p R_\text{PC}^{2}) \tag{9.9.14}$$

$\hspace{16pt}$ and so the recursion should limit $n$ to $n\leq t+u+v$.

In 2-electron integrals, the Hermite integrals are bound by $t \leq l_\mu + l_\lambda + l_\nu + l_\sigma $. Therefore $n$ is bound by the sum of the total angular momenta of the basis functions, i.e. $n \leq L_\mu + L_\lambda + L_\nu + L_\sigma$ where $L_\mu = l_\mu + m_\mu + n_\mu$.
Therefore, considering the extreme case of four $L=3$ basis functions, $n$ should be bound by $n \leq 12$.

Does this mean that a lookup table should start at $n=12$ and always recur down from this, or should I make different lookup tables and assess which one to use depending on the largest angular momentum functions in each individual computation? Are there any flaws or holes in my above logic?

All equations taken from Molecular Electronic Structure Theory, Helgaker et al. (2000).


texts: Graph of compounds/reactions used on the industrial scale

texts:
I'm looking for a machine-readable database describing industrially useful reactions in terms of inputs, outputs, and (possibly) catalyzers etc. for a large portion of, or (much more preferable) the entire organic and inorganic chemistry. A tall order, I know. Non-free, paywalled data references are acceptable, although free datasets are better.

As an example:

1-Aminoanthraquinone -> Alizarin
1-Aminoanthraquinone -> Mitoxantrone

EDIT: There's of course the Wikipedia, yet I cannot currently find out how to use Wikidata to mine the relationships between compounds. Many Wikipedia articles cite Ullmann's and other chemical cyclopaedias but I'm unaware of the latter having been converted into machine-readable form.


texts:
I, and a number of friends, take a bunch of supplements that are polyphenols and often flavin-oids, -ols or -es; also numerous carotenoids.  Examples include quercetin, luteolin, fisetin, curcumin, resveratrol or pterostilbene, apigenin, lycopene and astaxanthin.  Most of them are available in a relatively inexpensive, more or less pure form, and in a much pricier lipid nanoparticle form. The latter is justified because most of these substances are poorly absorbed, and lipid encapsulation has been shown to improve this.
When I look at the ingredients used to produce these lipid nanoparticles, they are generally cheep and easily available. They usually include some lecithin fraction, like phosphatidylserine or phosphatidylcholine, non-toxic organic solvents like propylene glycol or polyethylene glycol, and water or ethyl alcohol or both. You can get all these things from Amazon. So I was looking at this list, and I thought:
Mayonnaise.
I’ve made mayonnaise at home with just a blender. It’s not hard, but it is tricky. Try dribbling the aqueous part into the oil a few drops at a time, rather than the other way around. I’ve done this, and it never emulsifies.
So I have this idea that there should be, or at any rate there might be, a recipe for self-assembling lipid nanoparticles that could be made using kitchen equipment, that could be used to improve the nonavailability of a wide range of polyphenols such as those listed above, at lower cost and with greater satisfaction then having someone else do it and deliver it in capsules. And I was hoping that someone here might know of one, or where I could find one.
Based on my very limited exposure to the literature, I think the model I am aiming for is a colloid of nanoscale balls of one or more polyphenol dissolved in a lipid or a non-polar solvent, with a "skin" of phosphatidyl-something, in a mainly water matrix. I should add that all of these polyphenolic substances are marketed as supplements and considered to be foods under FDA rules.
Of all the things I don't know, I think the thing that would help me the most would be suggested identities for a GRAS lipid or lipid-like solvent that is good at dissolving many polyphenols, under atmospheric pressure and temperatures below the boiling point of water.


texts:
I have seen many pictures of chromium, and it's pretty lustrous as I must say. Here are some examples. Is it the most lustrous metal known?

Edit: By lustre, I mean suppose if we have a mirror smoothly polished made out of a material, then I consider lustre as the percentage of reflection of light within the wavelength of visible light (400 - 700 nm). Then according to this scheme, can we consider chromium as the most reflective for visible spectrum?


texts: What is the difference between ab initio calculations and molecular orbital theory?


texts: Role of phosphoric acid in redox titrations

texts:
For redox titrations of $\ce{Fe^2+}$ versus $\ce{KMnO_4}$ or versus $\ce{K_2Cr_2O_7}$  , role of phosphoric acid is quite unclear to me. In dichromometric titration, $\ce{H_3PO_4}$ complexes $\ce{Fe^3+}$ and thus lowers the  potential of the $\ce{Fe^3+/Fe^2+}$ system, but if it is a permanganometric titration, $\ce{H_3PO_4}$ strictly complexes to mask the yellow colour of $\ce{FeCl_3}$ but plays no part in lowering the potential of the $\ce{Fe^3+/Fe^2+}$ system. (role of ZR solution if $\ce{Cl-}$is present in the system )

My professor strictly mentions this as a key point of difference between roles of phosphoric acid in these two types of titrations and we cannot write the lowering potential point for the latter but that makes no sense to me. I do not understand why $\ce{H_3PO_4}$ in titrations versus $\ce{KMnO_4}$ will not reduce the potential of $\ce{Fe^3+/Fe^2+}$ system.


texts: Calculate Rate constant, k, for a consecutive reaction where k1<<k2

texts:
I have a consecutive reaction where the first step is the rate determining step so $k_1<<k_2$:

$$\ce{A ->[$k_1$] B ->[$k_2$] C}$$

The rate law can be shown to be:

$$[\ce{C}] = {1 - \exp(-k_1t)} [\ce{A}]_0\tag{eq. 1}$$

My reaction is pseudo first order since the first step is a hydrolysis. If I take the natural log of eq. 1 will I be able to convert it into the following form?:

$$\ln[\ce{C}] = -k_1t + \ln[\ce{A}]_0\tag{eq. 2}$$

... because If I could get it to this form, I will be able to plot $\ln[\ce{C}]$ vs $t$ to get $k$ from the slope.

If I have made a mistake with the natural logarithm (or if it is not possible to convert it to the form of eq. 2), what function do I need to use to find $k$?

My question is specifically: What do I need to plot to determine my rate constant considering I have done a time course NMR experiment?


texts:
Suppose I run a reaction and then pass the results through LC/MS to find the conversion. One idea could be to compare the peaks of the reactants to the peak of the product. But:

MS peak will depend on the levels of ionization of each of the compounds
UV spectra depends on the molar extinction coefficient of the compounds

So it looks like I can't compare the peaks. Is this right and if so what are the possible ways of finding the conversion?


texts: Crystallization in a solution of 2 or more solutes

texts: This is a very basic question I found myself wondering. For simplicity's sake, we'll say it is a super saturated aqueous solution of an equivalent measure of sugar and salt. As the solution cools and crystals form, do you get sugar crystals, salt crystals, cocrystals or discrete crystals of both?


texts:
At school, I learnt about the metal and their flame colour. Here's my observations.

$\ce{K^+}$- Lavender

$\ce{Ba^2+}$- Yellow-Green

$\ce{Ca^2+}$- Yellow-Red

$\ce{Li^+}$- Flame Red

$\ce{Na^+}$- Bright Orange

$\ce{Cu^2+}$- Blue-Green

So, my question is why do the each metal has its own flame colour?


texts: Defining an acid-base reaction from the perspective of the Arrhenius theory of acids and bases

texts:
$$\ce{NH3 + HCl -> NH4Cl}$$

The above equation is the reaction of ammonia with hydrochloric acid (all substances are aqueous). I understand that ammonia counts as a base because it can react with water to give hydroxide ions, and $\ce{HCl}$ is an acid. By logic, this should be an 'acid-base' reaction and this link
says that it is indeed an acid-base reaction but how is this so if no water is produced?

I am learning acid-base theory from the beginning and can understand why this is an acid base reaction from the perspective of the Brønsted-Lowry theory and the Lewis theory, but I am now attempting to understand the Arrhenius theory, so please explain to me, in terms of the Arrhenius theory, why this is an acid-base reaction and a 'neutralistaion' if there is no water produced and no hydroxide ions which take place in the reaction what so ever?


texts: Understanding a passage related to salt buffer

texts:
Passage from my textbook:

Are reactions possible among any of the solution components; is so, what is their stoichiometry?
Suppose that you are asked to calculate $[\ce{OH-}]$ in a solution that is prepared to be $\pu{0.10 M}~\ce{NaOH}$  and $\pu{0.20 M}~\ce{NH4Cl}$. Before you answer that $[\ce{OH-}]=\pu{0.10M}$, consider whether a solution can be simultaneously $\pu{0.10M}$ in $\ce{OH-}$ and $\pu{0.20M}$ in $\ce{NH4+}$ . It cannot; any solution containing both $\ce{NH4+}$ and $\ce{OH-}$ must also contain $\ce{NH3}$. The $\ce{OH-}$ and $\ce{NH4+}$ react in a $1:1$ mole ratio until $\ce{OH-}$ is almost totally consumed:$$\ce{NH4+ +OH- ->NH3 + H2O}$$
You are now dealing with the buffer solution $\pu{0.10M}~\ce{NH3}-\pu{0.10M}~\ce{NH4+}$

I am having trouble understanding the third last sentence in the paragraph that starts with "2." The statement reads: "It cannot; any solution containing both $\ce{NH4+}$ and $\ce{OH-}$ must also contain $\ce{NH3}$. The $\ce{OH-}$ and $\ce{NH4+}$ react in $1:1$ mole ratio until $\ce{OH-}$ is almost totally consumed"
Can someone please help me out with understanding this passage?


texts: Does mercury (I) chloride react with HCl?

texts:
If solid $\ce{Hg2Cl2}$ is placed in concentrated $\ce{HCl}$, will it react?
If so are the products $\ce{Hg2^2+}$, $\ce{H2}$, and $\ce{Cl2}$ ?

$$\ce{Hg2Cl2(s) + 2HCl(aq) -> Hg2^2+ + 2Cl2(g) + H2(g)}$$

I am teaching predicting products on a Chemistry I level, and I am not familiar with the subtleties of mercury chemistry. The short answer is "no reaction" because our "rules" state that a double displacement must occur with both reactants in aqueous solution. But I am seeking the reality behind the theory.

The entropy change would favor the reaction since it yields 4 mole of gasses from 1 mole of solid and 2 mole of solution.


texts: Can compounds found in concrete leach into soil against gravity?

texts:
I spent a while trying to figure out which stackexchange site in which to post this question, forgive me if I got it wrong.

A number of scholarly articles indicate that concrete can leach calcium compounds under the right conditions. Could they ever wick upwards against gravity through dry or water-saturated soil?

An example would be a raised bed of soil with wooden sides and a concrete floor.

P.S. I also wonder about plastics leaching upwards, but this is admittedly most likely a different question.


texts:
Is equilibrium between dissolution and recrystallization of a salt in an aqueous solution reached only when the solution is saturated; or can this also be established in an unsaturated solution?

Will Le Chatelier's principle apply in this situation (as it is about chemical equilibria)?

I was actually studying purification of salt by common ion effect where salt crystallizes from saturated aqueous solution on addition of common ion. Will the salt still crystallize if solvent still can dissolve more of it in unsaturated solution on addition of little amount of common ion. Since this crystallization is consequence of Le Chateliers principle, will crystallization still occur if solution taken was unsaturated and the common ion added is also in very small amount?


texts: Is there any software to simulate a laboratory?

texts:
I wanted to do some experiments with some chemicals but unfortunately I do not have access to them. Is there any software I can use to get the products?

I don't want to do very complicated things, I just want to gain some experience in basic chemistry, with simple chemicals like $\ce{H2O2}$, some salts, sulfuric acid, potassium permanganate, etc.

I tried to search on the net but most of the software I found is too complicated for me.

Do you know about any such software? Or do you have any alternatives?


texts: How to calculate the oxidation state and the number of equivalents oxidized with YBa₂Cu₃O₇

texts:
I've hit some trouble with these calculations and need help sorting out confusion.

In the lab we synthesized $\ce{YBa2Cu3O7}$, per the lab manual $\ce{Y, Ba, O}$ have the usual charges of +3, +2, and -2 respectively. Spectroscopic studies show that no copper (III) centers are present in the material, but rather there are missing electrons from the copper-oxygen bonds. For the purpose of the titration though, the missing electrons are thought of as coming from the copper center and we're assuming there are copper III centers present.

We used idodine to tritrate, and there is the assumption that copper is doing the oxidizing. The text states, "Copper(I) is not an oxidizing equivalent: It cannot oxidize iodide to iodine."

The relevant equations are
$$\begin{align}
\ce{Cu^{3+} + 2I- &-> Cu+ +I2}\\
\ce{Cu^{2+} +I- &-> Cu+ + \frac{1}{2}I2}
\end{align}$$

I've calculated the theoretical OS to be
$$\ce{Y} (3^+ )+\ce{Ba} (2^+ * 2)+\ce{O} (2^-*7)= \frac{7}{3 \ \ce{Cu}}\ce{Cu}^{2.3+}$$

We have to calulate the theoretical number of equivalents of $\ce{I-}$ oxidized by 1 g of the sample.

Would this be correct for the oxidation state? If so would that mean that the total equivalents of Iodine are an addition of $\ce{Cu(II)}$ and $\ce{Cu(III)}$ (the two equations)? Also I'm feeling brain dead, because I can't figure out the fraction of $\ce{Cu(II)}$ and $\ce{Cu(III)}$ that would average to 2.3.


texts:
Is there a way to test if water has toxic heavy metals. Samples to both the water and people who drink it are available. Preferably, it should be done with at hold materials. I could also borrow materials from a high school chemistry lab potentially.

I have already tried boiling, but that just showed that it is hard water, which luckily isn't dangerous. Any ideas?


texts: Manufacturing coloured crystal glass using gold nanoparticles

texts:
I came across this video which shows how a crystal chandelier is made. I recommend that anyone reading this post should watch it; it is quite fascinating.

Anyway, at about the 2:15 mark, the video talks about how ruby red crystal is produced by adding 24-karat gold powder to the glass. However, they say the colour emerges after reheating in an oven at $1000\ ^\circ C$.

My question is, why is the reheating step necessary ?


texts: The $\ce{.CH3}$ radical is planar but the $\ce{.SiH3}$ radical is a trigonal pyramid. Why are they different? After all, $\ce{C}$ and $\ce{Si}$ are in the same group.


texts: Why is the antibonding pi bond higher in energy than the normal pi bond?

texts:
In my book, Organic Stereochemistry, the following picture is shown:

In the lowest diagram, in Figure 1.3, which shows a π* bond, the positive lobe of the p orbital of atom A is nearest to the negative lobe of the p orbital of atom B. By contrast, in the diagram above it, which shows a π bond, the positive lobe of the p orbital of atom A is nearest to the positive lobe of the p orbital of atom B. It is said that the π* bond is higher in energy, less stable, than the π bond. I would have thought it to be the other way around, due to electrostatic repulsion when two lobes of p orbitals which have the same charge overlap, and the electrostatic attraction when two lobes of p orbitals which have opposite charges overlap.

Why am I wrong? Why is it not this way around?


texts: How do we count charges in this example of a Redox reaction equation?

texts:
My brother(younger) had a doubt regarding this chemistry book example so I let him here :

Question :

Balance the equation : $\ce{H+ + MnO4- + Fe^2+ -> Fe^3+ + Mn^2+}$

Solution steps(as given by the textbook):

Step 1 :  $$\ce{MnO4-  ->  Mn^2+}$$

Step 2 : $$\ce{MnO4-  -> Mn^2+ + 4 H2O}$$

Step 3 :  $$\ce{MnO4- + 8 H+  -> Mn^2+ + 4 H2O}$$

Step 4 : $$\ce{MnO4- + 8 H+ + 5 e- -> Mn^2+ + 4 H2O}\tag{1}$$

Step 5 : $$\ce{Fe^2+ -> Fe^3+ + e-}\tag{2}$$

Step 6 : $5\times(2) + (1)$ and thus we have the balanced equation:

$$\ce{MnO4- + 8 H+ + 5 Fe^2+ -> 5 Fe^3+ + Mn^2+ + 4 H2O}$$

Explanation given in the textbook for step 4:  we equalise the charge by adding 5 electrons on left.

My doubt regarding step 4: how do I know that in step 4 that 5 electrons do actually equalize the charge in the given equation? More accurately how do I know that there is any surplus or deficit of charge in any given equation atleast in this case?


texts:
The setting of this problem is on the moon of Jupiter: Io.

  Given that chlorine exists in two isotopes: $\ce{{}^{35}_{17}Cl}~(33.3\%)$ and $\ce{{}^{37}_{17}Cl}~(66.7\%)$, what is the mass spectrum of $\ce{Cl3+}$?

What I know now is that there are 3 peaks in the mass spectrum of $\ce{Cl2+}$ because there are 3 possible combinations ($\ce{{}^{35}_{17}Cl}$ + $\ce{{}^{35}_{17}Cl}$ / $\ce{{}^{35}_{17}Cl}$ + $\ce{{}^{37}_{17}Cl}$ / $\ce{{}^{37}_{17}Cl}$ + $\ce{{}^{37}_{17}Cl}$). Therefore, there are 4 possible combinations and 4 peaks for $\ce{Cl3+}$.

However, I do not know how to make a mass spectrum graph with only this much information.


texts: Calculation of the specific rate constant (k)

texts:
Suppose we found that the reaction of Red#3 with bleach is 1st order in hypochlorite. The observed rate constant ($k_\mathrm{obs}$) for one of the trials was measured to be $\pu{0.00400 s^{-1}}$. If the concentration of hypochlorite was fixed at $\pu{0.134 M}$, calculate the specific rate constant ($k$) for that trial.

I am very confused in which equation I should use to solve this problem. Am I to use this equation?
$$\mathrm{Rate} = k[A]^m[B]^n$$

If that is the case, for trial #1:

$$\mathrm{Rate} = \pu{0.00400 s^{-1}} \times \pu{0.134 M} = \pu{5.36e-4 mol L^{-1} s^{-1}}$$

But then what should I do next? This does not sound right. Please point out my mistakes.


texts:
As we know, dimers, trimers etc. can be produced from a certain amount monomers. In the case of a dimer being produced, two monomers dimerise.

Let's take an example of a dimer (glycine anhydride):

Two glycine monomers were dimerised for this - it's a dimer since it has 2 (poly)amide bonds.

Now, let's take an example of an ester (ethyl ethanoate):

This is where my question comes in: would it not be appropriate to call ethyl ethanoate a monomer? As we saw with glycine anhydride, it has two (poly)amide bonds, hence it's a dimer. Ethyl ethanoate has a single ester bond, so would this not render it as a monomer? Or is this incorrect logic, since ethyl ethanoate isn't an oligomer/polymer per se?

P.S. I sometimes put the word 'poly' in parenthesis since I'm not sure whether its usage is necessary in description.


texts: Are the reaction rates of these equations equal?

texts:
$$\ce{CH3CH2CH2Br + OH- -> CH3CH2CH2OH + Br-}$$

$$\mathrm{rate} = k[\ce{CH3CH2CH2Br}][\ce{OH-}]$$

If I change the $\ce{Br}$ with any element from halogens (without changing concentration, volume, mass etc.), does the rate of reaction change? If so, how does it change? What factors change it?


texts: Why does coconut oil spoil much faster than groundnut oil?

texts:
I have observed that various foods cooked using coconut oil spoil much faster than foods cooked using groundnut oil. One good example is Asian coconut milk curry. Even with proper refrigeration, this food item cannot last more than 2 or 3 days typically. This is in very sharp contrast to food items cooked with groundnut oils which can last for much longer, possibly a few weeks. I have been looking up various Internet sources and some have cited the presence of natural enzymes, such as lipoxygenases and peroxidases, which are present in these coconut oils, while oils like groundnut oil and palm oil, do not contain these natural enzymes.

Looking at the chemical composition of the fats was also something I did. As shown here, most of the fatty acids found in coconut oil are saturated fatty acids, with lauric acid making up a large part of them. In fact, as shown here, groundnut oils seem to contain more unsaturated fatty acids than coconut oil, which we would expect to be more reactive and liable to degradation. Thus, the difference in the composition of the fats in the oils may not be what is responsible for the observed quicker rate of spoilage of coconut oil.

I would like to ask if anyone knows more to share regarding this issue. For now, it seems that the presence of enzymes may be the likely underlying reason for the faster rate of spoilage of coconut oils.


texts: Does the distillation of alcohol cause the fractioning of isotopes and carbon-12 enrichment?

texts:
In water, distillation causes fractioning of the $\ce{^{18}O}/\ce{^{16}O}$ oxygen isotopes (Wikipedia).

Does something similar happen to the $\ce{^{13}C}/\ce{^{12}C}$ and possibly $\ce{^{14}C}$ isotopes in alcohol when it is distilled out of a watery brew?


texts:
The synthetic scheme below makes reference to a reagent $\ce{(CH_3)_3COCl}$  that is added at some points in the synthesis.

What kind of structure does $\ce{(CH_3)_3COCl}$  have? The closest structure I can imagine is that of $\ce{(CH_3)_3CCOCl}$ with an extra carbon for the 3 methyl groups to be attached to. $\ce{(CH_3)_3COCl}$ seems to imply that the 3 methyl groups are attached to the carbonyl carbon (which is impossible).

Image source: IChO 2015, Problem 6


texts:
Under certain conditions, the well-known fertilizer $\ce{NH4NO3 (s)}$ explodes according to the following balanced reaction:

$\ce{2NH4NO3 (s) -> 2N2 (g) + 4H2O (g) + O2 (g)}$

Exactly 8 g of $\ce{NH4NO3}$ is placed in a 1.18 L constant-volume container containing dry air at 56.01 kPa and 15 ºC. The explosive reaction goes to completion and the temperature rises to 527 ºC. The container remains intact after the explosion. Determine the mole fraction of N2 in the gas phase after the explosion.

Data: Assume that the composition of dry air is 79% N2 and 21% O2 by volume.

So I know that $\ce{N2}$ takes 0.9322 L of volume. I calculated it by 0.79*1.18 = 0.09322

The only thing that I don't know is the number of moles, so do I just use the formula of ideal gas law which is $PV = nRT$,
 P = 0.5528 atm( 56.01kPA) V = 0.09322

However, which temperature should I use?
And am I using the right approach for this problem?


texts: Catalysist activation energy - the Brønsted-Evans-Polanyi relation

texts:
I have stumbled upon something called the Brønsted-Evans-Polanyi relation in a study about the design of catalysts (for reactions like those in hydrocracking fuel production.)

The relation shows that the transition state potential energy $E_a$ is linearly related to the CO dissociation energy (over transition metal surfaces):

Reproduction of Fig. 3B from J.K. Nørskov et al, Nature Chem. 2009, doi:10.1038/nchem.121

My question is simply: What exactly is on the axes?

I am not sure if the transition state potential energy $E_a$ is the same as the $E_a$ being described in e.g. the linked Wikipedia article in the first paragraph. Is it a term for the activation energies that belong to the intermediate steps, when the catalyst breaks down the original activation energy jump into more smaller jumps?
The CO dissociation energy is a bit odd for me. Is this the energy for adsorption of CO into the material surface?

According to the Wikipedia article, this relation in the graph should be given by the equation:

$$E_a=E_0+\alpha \Delta H$$

where $\alpha$ seems to be a constant and $\Delta H$ the enthalpy of reaction. This seems to say that my "CO dissociation energy" on the $x$-axis is the enthalpy (or the product of enthalpy with $\alpha$.) I would appreciate if someone could shed some light on the wording "CO dissociation energy".


texts: Is “amount of substance” the same thing as “number of moles”?

texts:
Background:
Amount of substance is a fundamental physical quantity which has mole (mol) as it's SI unit. Therefore all expressions for amount of substance should have the unit mole on simplification.
If $A$ is the amount of substance (normally in moles), $m$ is the mass of the substance in a particular unit (normally in grams), $M$ is the mass per unit amount of substance (normally in grams/mole), then
\begin{align}
A &= \frac{m}{M}\tag1\label1
\end{align}
If the substance is a molecule then $M$ is known as molar mass of the substance.
But in my textbook and in many websites on the internet, I have encountered the phrase number of moles. I think it refers to the amount of substance or maybe the numerical part in the amount of substance. The formulas given there were strange.
If $n$ is the number of moles, $m$ is the mass of the substance in grams and $x$ is the atomic weight (for atoms of elements) or molecular weight (for molecules of elements and compounds), then,
\begin{align}
n &= \frac{m}{x}\tag2\label2
\end{align}
This equation is not dimensionally correct if I am right.
My questions:
First of all I would like to ask whether amount of substance and number of moles refer to the same thing, or is it that amount of substance has a unit along with a numerical value whereas number of moles does not have a unit and represents the numerical value in the magnitude of the amount of substance.
Secondly, between equations $\eqref1$ and $\eqref2$, which one is completely correct (both in meaning and dimension)?
Thirdly, since in some place I have encountered gram atomic/molecular mass in place of molar mass, I would like to know what are the differences between both and do they have the same units or different units?


texts: What's the smallest Hoberman sphere possible?

texts:
What is the smallest Hoberman sphere possible? Could it be possible on an atomic or molecular level?

Image courtesy of Hoberman Associates, Inc

I realize the issue with this will be the scissor joints. I am wondering how small these could be made and arranged. Would it be possible to create a functional Hoberman sphere with carbon nanotubes?

I am also curious if anyone has any opinion or knowledge about if it is possible to make a Hoberman “molecule” or rather a Hoberman sphere made of atoms? If so, what elements would make for the best Hoberman molecule? Could scissor joints be made functional at the molecular level both expanded and closed using something like redox reactions?

Thanks in advance for any answers!


texts:
In a talk by Frank Neese there was a slide with title "Nesbet's theorem" and an equation indicating something like "if your wavefunction has the double excitation amplitudes correct, then you can get the correct FCI energy for free". The caveat being that to get the doubles exactly correct you need the triples and quadruples, and to get the quadruples you need the pentuples and hexuples, etc.

Unfortunately I am not able to find this theorem stated precisely anywhere with a Google search. I have been told that the theorem can be found in the book Molecular Electronic Structure Theory by Helgaker, Jorgensen, and Olsen, however I do not have the book and need the precise statement of this theorem.

Does anyone know the precise statement of Nesbet's theorem and the original source?


texts: How does one refer to the amino acids in a peptide?

texts: Once a part of a peptide an amino acid is no longer an amino acid, so how do we refer to the part of the peptide that was once amino acid x?


texts: Why does Finkelstein reaction only work with R-Cl and NaI?

texts:
Why does Finkelstein reaction necessarily involve: R-Cl and NaI (in Acetone)? Why can it not be done with KI? How does potassium instead of Sodium affect the reaction? Why can't R-I react with KCl in the same way?

(I've not included R-I (Iodine) or Fluorine (in the ionic compound) since they are extremes and are very slow or violent in many reactions respectively.)


texts: Is the electron configuration redundant?

texts:
For example the electron configuration for oxygen is 1s2 2s2 2p4. But if an element can never have an element in the p orbital unless it has 2 full s orbitals*, then why can't we write 2p4 as the electron configuration for oxygen? Is it not implied that it has 1s2 2s2? I would think so because the noble gas configuration works on a similar principle.

*My teacher told me this.


texts: Does ethanol react with potassium to form potassium ethanolate and hydrogen gas?

texts:
I'm finding information in Google with the keyword (C2H5OH + K) to find the reaction between $\ce{C2H5OH}$ and $\ce{K}$ and found very little information about it. Just 2-3 related results with contradictory pieces of information.

The first one gave

$$
\ce{K + C2H5OH -> KOH + C2H5},
$$

the second one gave

$$
\ce{2C2H5OH + 2K -> 2C2H5OK + H2},
$$

and the third one gave

$$
\ce{C2H5OH + KOH -> C2H5OK + H2O}
$$

There are no trusted public sources so I'm very baffled. I think that $\ce{C2H5OH}$ will react with $\ce{K}$ to form $\ce{C2H5OK}$ because it looks like the reaction with $\ce{Na}$. But I'm not sure and just want to find a trusted source. Can anyone confirm the true result for this reaction?


texts: Why are Alcohol Dehydration Reactions Favored by High Temperatures?

texts:
If I go by the Gibbs' free energy formula, it makes sense that high temperatures make the dehydration of alcohols more feasible, as elimination reactions usually have a positive value for the change in entropy ($\Delta S$) and the hydration of the sulfuric acid used is highly exothermic ($\Delta H$). This decreases the value for the change in free energy ($\Delta G$).

However, if I go by the modified Vant Hoff's formula (relationship between an initial equilibrium constant at an initial temperature and a final equilibrium constant at a final temperature), the $K_2/K_1$ ratio would be higher at lower temperatures, owing to the product $\Delta H \Delta T$ being positive (rather than negative if the reaction mixture is heated).

These are the formulas I'm referring to:

\begin{align}
\frac{K_2}{K_1} &= \exp{\left(\frac{\Delta T \Delta H}{RT_1T_2}\right)} \tag{1}\\
\Delta G &= \Delta H -T \Delta S \tag{2}
\end{align}


texts: Are there ethanol and methanol analogues with more than one hydroxyl group?

texts: Ethanol and methanol are ethane and methane derivatives, respectively, with one hydrogen replaced by an hydroxyl group. Are there molecules based on either where more than one hydrogen atom has been replaced by an hydroxyl group? If so, what are they called?


texts: Shape of the container and the number of possible energy states

texts:
A question came up when studying the formula for calculating the total number of possible energy states of a particle within a container.

Why is the number of possible energy states independent of the shape of the container and merely dependent on the number of states in only 3 perpendicular container dimensions ($x$, $y$ and $z$), while a momentum vector can be directed at any direction within the container? Shouldn't the length of the container in that same direction as the momentum vector also determine the number of energy states in that direction?


texts: Reduction of amides with lithium aluminium hydride

texts: Since $\mathrm{p}K_\mathrm{a}$ of primary amides are close to alcohols, will there be an acid-base reaction between amides and $\ce{LiAlH4}$ besides reduction?


texts: Diffusion-controlled reactions, activation-controlled reactions and rate equation

texts:
I am confused as to where the rate equation can be applied and where not to be applied.
https://en.wikipedia.org/wiki/Rate_equation

In diffusion-controlled reactions from what I understand reaction rate is analogous to substrate concentration and the rate determining step is the supply of substrate.
https://en.wikipedia.org/wiki/Diffusion-controlled_reaction

But in activation-controlled reactions does the same apply?
Does reaction rate also depend on substrate concentration?


texts: Alternate pathway of Gabriel synthesis to prepare secondary amine

texts:
Can modifying the Gabriel synthesis, which is generally restricted to synthesis of primary amines, be used to synthesise secondary amines?
I have attached my idea regarding the synthesis (the final product obtained is a phthalic acid):


texts: What's the difference between Gibbs Energy and Work?

texts: Gibbs energy is usually defined as the maximum useful work that a system can do on its surroundings. So what's the main difference between Gibbs energy and work?


texts: Why is the force constant for double and triple bonds approximately double and triple of that of a single bonds?

texts:
I am new to spectroscopy, and I am referring to Donald Pavia's Introduction to Spectroscopy. I came across this statement in the book, under the chapter Infrared Spectroscopy:

  $K$ is a constant that varies from one bond to another. As a first approximation, the force constants for triple bonds are three times those of single bonds, whereas the force constants for double bonds are twice of those of single bonds.

As far as I know, double bonds are not considered as two single bonds. Double bonds are rather one $\sigma$ bond, and one $\pi$ bond. Neither the bond energies of double bonds are twice the energy of corresponding single bonds, nor is the bond length of double bonds half of the single ones. Then how is the force constant doubles as the bond order doubles?


texts:
I noticed after some use that a stainless steel spoon that I have started forming $\ce{FeO}$. Stainless steel is not supposed to rust like this. I don't know of any black iron hydroxides, chromium oxides, or chromium hydroxides so that lead me to deduce that it is Iron(II) Oxide.

But why would stainless steel oxidize? I mean it does not make any sense since I was told that stainless steel does not oxidize.

And how can I get rid of the oxide? Putting the spoon in phosphoric acid perhaps since phosphoric acid is a really good rust remover?


texts: How does an energy input actually change a molecule?

texts:
I'm reading an online biochemistry textbook for fun, and a question that has bothered me on chemistry before popped up again. The question here is not specific for the chemical process described, but I needed an example:

By adding energy to a molecule of formic acid ($\ce{CH2O2}$), it kicks out an O and becomes formaldehyde ($\ce{CH2O}$). More energy makes it methanol ($\ce{CH3OH}$), and more energy makes that methane ($\ce{CH4}$).

I get that energy allows the molecule to become a different molecule of a higher energy state; it essentially stores the energy as new or altered chemical bonds. What I never understood is why? It is natural for the molecule to try to go to a lower energy state, releasing energy in the bonds, as it does under oxidation/"burning". So why doesn't it just immediately release the added energy, rather than store it in bonds?

What prevents the formaldehyde from saying "I see your energy, but I'll just do what's easier for me and release some of my own, and become formic acid"? After all, no matter how much energy I use to blast a block of stone into the air, it's going to fall down again, unless someone up there catches it. What's "catching" the higher-energy molecule and preventing it from "falling back" into the more stable, lower-energy molecule?

The answer seems like it might be leaning on atomic theory more than chemistry, but I thought I'd give it a shot here.


texts:
An end-chapter problem posed in an 11-grade texbook asks to analyse whether a water solution of CuSO4 will be acidic.

The standard answer is yes, because "$\ce{H2SO4}$ is a strong acid, hence $\ce{SO_4^2-}$ is a weak base. As a weak base, it will not be too hot about grabbing $\ce{H^+}$ from the environment. On its part, $\ce{Cu^2+}$ will strongly attract $\ce{OH^-}$ groups, and overall protons will prevail over hydroxides."

But I was told in the chat that the real answer is more interesting and complicated, so I post this question in the hope that someone will explain the process in-depth.


texts:
I wrote a piece of code on RHF using Python a while back, and figured I'd extend it to also implement CNDO/2 (yes, I know it's old but I figured it'd be easier for me.)

The approximated Fock matrix elements, taken from the original paper, are as follows:

$$F_{\mu\mu} = U_{\mu\mu} + [(P_{AA} - Z_A) - 0.5(P_{\mu\mu}-1)]\gamma_{AA} + \sum_{B ≠ A}(P_{BB} - Z_B)\gamma_{AB} $$

$$F_{\mu\nu} = \beta_{AB}^0S_{\mu\nu} - 0.5P_{\mu\nu}\gamma_{AB}$$

where $U_{\mu\mu}$ is an empirical parameter measuring "orbital electronegativity", $P_{AA}$ measures the total electron population on atom $A$, and $P_{\mu\mu}$ measures the electron population of basis function $\mu$.

Unfortunately, I got quite unusual results (read: the lowest orbital energy being about $-50$ hartrees) when I tested this approximation on molecules like $\ce{CO2}$ or $\ce{H2O}$. (I used a STO-3G basis set from Basis Set Exchange).

For the population terms, I used the formula $$P_{\mu\mu} = 2\sum_{i, \mathrm{occ.}}c_{\mu i}^2$$

and

$$P_{\mu\nu} = 4\sum_{i, \mathrm{occ.}}c_{\mu i}c_{\nu i}S_{\mu\nu}$$

and accordingly defined $$P_{AA} = \sum_{\mu ∈ A}P_{\mu\mu}$$

Is there something wrong with my equations?


texts: Reason behind conversion of acid to acid bromide in Hell-Volhard-Zelinsky reaction

texts: Why in Hell-Volhard-Zelinsky (HVZ) reaction the acid is first converted to acid bromide by using $\ce{PBr3}$ and then alpha halogenation is carried out?


texts: Many diagrams of orbitals I've seen involve electrons moving through a center point—where the nucleus is. How can this be? Clearly they don't actually pass through the nucleus, so what does happen?


texts: Determine most electronegative element based on successive ionization energy data

texts:
X, Y and Z are three unknown elements whose first 5 ionization energies are given below. Which of the 3 is the most electronegative?$$
\begin{array}{|c|c|c|c|c|c|}\hline
&\text{IE}_1&\text{IE}_2&\text{IE}_3&\text{IE}_4&\text{IE}_5\\\hline
\ce{X}&577&1815&2740&11600&15000\\\hline
\ce{Y}&800&2427&3660&25026&32827\\\hline
\ce{Z}&738&1451&7733&10543&13630\\\hline
\end{array}
$$

Because of the IE ratios, I concluded that X and Y are in the third column and Z is in the second column. I know that EN increases from left to right for elements in the same row. Is there anything else I should know in order to solve this?


texts: Applying Henderson–Hasselbalch equation to amino acids: which pKa to use to calculate Z-/HZ ratio?

texts:
I was wondering which $\mathrm{p}K_\mathrm{a}$ to use when calculating the ratio of $\ce{HZ}$ to $\ce{Z-}$ of amino acids, the Henderson–Hasselbalch formula used:

$$\mathrm{pH} = \mathrm{p}K_\text{a} +\log\frac{[\ce{Z-}]}{[\ce{ZH}]}$$

Because most amino acids have two $\mathrm{p}K_\mathrm{a}$'s, one for the amino group and one for the carboxyl group (and sometimes a third $\mathrm{p}K_\mathrm{a}$ for the side chain). For example, leucine:

$$\begin{array}{cc}
\hline
\text{Residue} & \mathrm{p}K_\mathrm{a} \\
\hline
\ce{NH3} & 9.74 \\
\ce{COOH} & 2.33 \\
\hline
\end{array}$$

Let's say I want to know the ratio of $\ce{HZ}$ to $\ce{Z-}$ for a $\mathrm{pH}$ of $1.00$ and $11.00$, which $\mathrm{p}K_\mathrm{a}$ should be used in the Henderson–Hasselbalch equation and why?


texts: Why does nitric acid not turn yellow everytime?

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I have dilutions of different samples, which are made with 0.1 M $\ce{HNO3}$. Only I left them on the lab table for a few days and one turned yellow.

So my question is why would one turn yellow and not the other ones? They all have the same concentration of sample. The matrix in all the samples are the same. The difference is the concentration of $\ce{Cl-}$ in the samples. The one with the lowest concentration of $\ce{Cl-}$ turned yellow.

Any ideas why?


texts:
Our lab uses a sodium hydroxide solution of a (theoretically) known normality (0.8000 - 1.0000) to titrate product samples for quality control.  However, we suspect that the normality of the $\ce{NaOH}$ left in the burette/tubing connected to our container is changing if we let it sit (our tests come out wrong, and the answers seem to get better if we run a couple of burettes worth of $\ce{NaOH}$ out first).  I expect it's absorbing moisture from the air, but I don't know for sure.

We've tried different container types and we've put a desiccant in line with the tubing to absorb stray moisture (which it seems to be doing, there's been an observable color change), but the situation remains that we need to just throw out up to 200mL of $\ce{NaOH}$ any time we need to run a test.  Does anyone on here have any recommendations for countering this normality drift?


texts: If alkyl-substituted alkenes are more stable, how does one explain their increased addition reactivity?

texts:
My understanding is that in alkyl-substituted alkenes there is hyperconjugation between $(\ce{C−X})$ and $^∗(\ce{C=C})$. I also have read that more alkyl-substituted alkenes are many folds more reactive in addition reactions. I understand how hyperconjugation stabilizes alkyl-substituted carbocations.

However, based on the fact that alkyl-substituted alkenes are more "stable", and the fact that the hyperconjugation between their $(\ce{C−X})$ and $^∗(\ce{C=C})$ causing a delocalization of electrons at the $\ce{C=C}$ double bond, wouldn't the alkyl-substituted alkene be less reactive? Obviously stability comes into play, and additionally the loss of electron density at the $\ce{C=C}$ double bond should mean that the $$ bond is less of a nucleophile so would prevent attraction of electrophilic addition.

One way I came up to justify this is maybe that the stability from the hyperconjugation of the carbocation outweighs stability from hyperconjugation of alkene. Or that somehow the hyperconjugation between $σ(\ce{C-X})$ and   $π^∗(\ce{C=C})$ adds electron density to the $^∗$ making it more attractive to electrophiles that can break the $\ce{C=C}$ double bond. Of course, I am only using these as justifications to fill in misunderstandings.


texts: How do I heat my borosilicate reflux column?

texts:
I am gonna use a ceramic tape heater, but cannot wrap it around evenly. Is the glass column gonna be okay?

I am running some tests on plastic pyrolysis. I am using the reflux condenser to make the heavier hydrocarbons flow back into the boiling flask. I am also trying out various catalyst in the reflux condenser which will facilitate catalytic cracking.

I have decided to maintain the temperature at top of the reflux column to be of 150C and it will allow the lighter fraction to be removed off and the heavier fraction to be condensed back into the boiling flask.

The boiling flask is made up of quartz and the rest of the glassware is borosilicate.

I am gonna use the glass setup to test catalysts. If results are satisfactory, will get a microreactor made up of steel for further testing. I can better monitor and control temperature in a metal setup I think. Gonna try on only PE and PP types of plastic.

I am a structural engineer by profession and am new to organic chemistry. Thanks for you help in advance.


texts:
I've made a battery for middle school, and I want to figure out the chemistry, especially so I can say whether the little bubbles in there are $\ce{CO_2}$ or hydrogen.

In salt water, I have a strip of magnesium, and a graphite bar. They connect outside of the jar with wires to an LED, and the cell produces a little electricity. The magnesium strip slowly corrodes, and as it runs it produces little gas bubbles on the magnesium.

I think the bubbles might be hydrogen, but my partner thinks they might be $\ce{CO_2}$. We've tried googling for equations for magnesium and carbon, but haven't found someone who seems to be talking about a cell like this. What's going on? Also, what is the stuff forming on the magnesium? Some of it seems to be flaking down to the bottom of the jar. I think it's some kind of magnesium oxide, but that's a guess.  Can someone guide us? Thanks!


texts: What methods could be used to preserve scorpion venom?

texts:
As extracting scorpion venom goes, how would one most effectively store and preserve the venom for future research?

My thoughts are lyophilization, however I am not sure that would be the best of all methods in this case. Thoughts?


texts:
In analyzing the solubility among $\ce{CaF2, CaCl2, CaBr2}$, I found that $\ce{CaF2}$ is insoluble due to high ionization enthalpy.

But comparing among $\ce{AgF, AgCl, AgBr }$, it was said  that $\ce{AgF}$ is more soluble because of Fajans' rules (consequence of polarization). $\ce{AgCl, AgBr}$ have high polarizing effect and so they have high covalent characteristics.

Now question is why can't I use the Fajans' rules at $\ce{CaF2}$? Where can I use Fajan's Rule and Where should I use Lattice enthalpy rule?

This problem is also present at comparing the melting point of $\ce{NaCl, KCl}$. Fajans' rules cannot be applied here also.


texts: What is the difference between organosilyl, alkoxysilane and silane compounds?

texts:
What is difference between organosilyl, alkoxysilane and silanes?

How do these groups make a surface hydrophobic?


texts: Why does atomic charge not balance in nuclear reactions?

texts:
In the discovery of neutron, the bombardment of beryllium with alpha particles is well known.

$$\ce{^9_4Be + ^4_2He^2+ -> ^12_6C + ^0_1n}$$

I don't understand how the electrons add up. As alpha particles do not have electrons, the total electrons should be 4 accounting for the electrons of beryllium, but after bombardment, there is a deficiency of 2 electrons in carbon atom. Shouldn't the $\ce{^12_6C}$ atom be positively charged? Like:

$$\ce{^9_4Be + ^4_2He^2+ -> ^12_6C^2+ + ^0_1n}$$


texts: C-F bond lengths of octafluoropropane using Bent's rule

texts:
I was trying to predict different $\ce{C-F}$ bond lengths of octafluoropropane,  $\ce{CF3-CF2-CF3}$ :

Applying Bent's rule here, we see that

For $\ce{C^2}$, we have $\ce{C^3}$ and $\ce{C^1}$ towards which s-character of $\ce{sp^3}$ orbitals is richer. Hence $\ce{sp^3}$ orbital of $\ce{C^2}$ has lesser s-character directed towards $\ce{F}$.
For $\ce{C^1}$ (or $\ce{C^3}$), we have only  $\ce{C^2}$ toward which  s-character of $\ce{sp^3}$ orbitals is richer. Hence $\ce{sp^3}$ orbital of $\ce{C^1}$ has greater s-character directed towards $\ce{F}$.

Using this I think $\ce{C^2 - F}$ bond length is greater than $\ce{C^1 - F}$.

Q. Is this explanation reasonable?

Q. Can we use Bent's rule to predict bond-lengths here or we should consider steric effects of $\ce{CF3}$ (trifluoromethyl) groups ? (here both lead to same result)

I mean in general on which rule should we rely on? On wikipedia article on Bent's rule its written that often times Bent's rule prediction would contradict predictions based on other classical effects alone (steric effects etc). In such cases how can we justify any prediction?

(Wikipedia) Bent's Rule - Bond lengths

  A prediction based on sterics alone would lead to the opposite trend, as the large chlorine substituents would be more favorable far apart. As the steric explanation contradicts the experimental result, Bent’s rule is likely playing a primary role in structure determination.


texts: Free Electron-Bond Electron Interactions

texts:
I am reading an introductory textbook on electronics: Practical Electronics for Inventors by Paul Scherz and Simon Monk. In a section discussing the motion of electrons in circuits, the textbook mentions something called free electron-bond electron interactions:

  It is likely that those electrons farther "down in" the circuit will not feel the same level of repulsive force, since there may be quite a bit of material in the way which absorbs some of the repulsive energy flow emanating from the negative terminal (absorbing via electron-electron collisions, free electron-bond electron interactions, etc.).

I have never heard of such bonds/interactions, and a quick Google search reveals nothing of the same description.

The description seems odd to me, since electrons repel rather than attract/bond.

I wonder if this could be in reference to metallic bonds? Metallic bonds are formed by the attraction between metal ions (of which circuitry components comprise) and delocalized, or "free" electrons (which is what is pumped out from the battery, as a result of chemical reactions within).

I would appreciate it if someone could please take the time to explain what these are, and/or please direct me to a source (Wikipedia article?) on this subject.


texts:
With which group does the middle oxygen atom of an anhydride remain, on hydrolysis? As an example, let us say we have the following modification of ethanoic methanoic anhydride, with the middle oxygen atom being the $\ce{^18O}$ isotope:

On acid catalysed hydrolysis with normal water, is this isotope found in formic acid, or acetic acid, or in both (i.e., hydrolysis is random and hence the product contains both the acids with both types of oxygen atoms)?