texts:
What are the options that I might be missing for the purification of a molecule with the following characteristic:

Contains an activated ester that reacts with water (NHS)
Reacts readily with alcohols
Does not elute on silica gel (typical or spherical) with THF, Acetone, EtOAc, DCM, or Acetonitrile
Is not a solid that can be precipitated, rather some horrible gum
Decomposes rapidly in prep-LC on C18 0.1% TFA (10% back to acid after 20min run in best cases) typical loss of material is about 50% from initial mass.
Greasiest solvent that solubilises is DCM

Impurities are mainly side product from NHS coupling reagents or relatively uncharacterized impurities with properties similar to final product.

Honestly, I have not much hope left to find something there but if you know of conditions what could provide separation in reverse phase HPLC with aprotic solvent, I'm all ears.

Edit: I'm open also to hear about volatile buffer system that could be in a pH range that would allow greater stability of the NHS in water.


texts: Comparing rates of hydrolysis in cyclohexane ring (involving neighbouring group participation)

texts:
I need to compare the rates of hydrolysis of these three compounds.

MY ATTEMPT:

By definition hydrolysis is either $\ce{S_N1}$ or elimination.But water being a weak base (and weak nucleophile) $\ce{S_N1}$ is preferable.
$\ce{PhS^-}$ is a better leaving group than $\ce{Cl-}$ due to mesomeric effects.
Comparing with the middle compound the leftmost and rightmost compound will certainly have higher rate of hydrolysis due to presence of good leaving group $\ce{PhS^-}$
But how to compare between the leftmost and rightmost compound's rates?


texts: Why is there no non-bonding molecular orbital in the overlap between H1s and Be2s in BeH2

texts: I've only recently started learning about this and I'm stating to get confused. (The orbital in the middle belongs to Be) So you have a + (+) + which gives a sigma bonding orbital and a + (-) + which gives a sigma anti-bonding orbital. Why isn't there a + (-) - which would result in a non-bonding orbital?


texts:
The reactivity of the enolate ion is most frequent explained with reference to its system of $\pi$ molecular orbitals. The image below taken from Wikimedia Commons depicts this system of $\pi$ molecular orbitals. $\ce {C}$-alkylation is favoured when the orbital interaction with the $\ce {HOMO}$ of the $\pi$ system is dominant while $\ce {O}$-alkylation is favoured when the electrostatic interaction with the negative charge built up on the oxygen atom is dominant. This is the case because the coefficient of the $\ce {HOMO}$ is the largest on the terminal carbon atom while being more electronegative, oxygen naturally bears greater negative charge.

The explanation provided by Fleming (2010) on p. 160 is that in the lowest-lying $\pi$ molecular orbital, the oxygen atom exerts the strongest polarising effect on the electron distribution while for the second highest $\pi$ molecular orbital, the polarisation is in the opposite direction. I understand that these MO diagrams are grounded in quantum chemistry theory but is there any way that we could intuitively understand why the coefficient of the $\ce {HOMO}$ is indeed the largest on the terminal carbon?

Update

After discussion with some friends, I have more thoughts I would like to share. There is this connection between resonance structures and MO diagrams. For example, the MO diagrams of the allyl cation and allyl anion feature a node in the second MO, informing us that there is no sharing of the charge with the central carbon atom. This information is also reflected when we draw the two resonance structures. Can we perhaps, extend this connection a little further and say that the first MO for this enolate $\pi$ system reflects the charge distribution in the resonance structure with negative charge localised on the oxygen atom while the second MO reflects the charge distribution in the resonance structure with the negative charge localised on the carbon atom?

Image source

Reference

Fleming, I. Molecular Orbitals and Organic Chemical Reactions (Reference ed.). United Kingdom : Wiley, 2010.


texts: Find increase in OH- ion concentration after base is added

texts:
The pH of a solution is 7.00. To this solution sufficient base is added to increase the pH to 12.0. the increase $\ce{OH-}$ ion concentration is:

  (A) $5$ times
  (B) $1000$ times
  (C) $10^5$ times
  (D) $4$ times

The answer is (C) $10^5$ times.

Now, the temperature hasn't been mentioned ergo we can't assume that it's a neutral soultion, right? So, I tried doing it this way:

\begin{array}{llll}
&\mathrm{pH} &= 7 &\qquad &\mathrm{pH} &= 12 \\
&[\ce{H+}] &= 10^{-7} &\qquad &[\ce{H+}] &= 10^{-12} \\
& & &[\ce{OH-}]~\text{added} \\
& & &= 10^{-7} - 10^{-12} \\
& & &= 10^{-7} (1 - 10^{-5}) \\
& & &\approx 10^{-7}
\end{array}

$[\ce{OH-}]$ added is the increase in its concentration, or so I think. I don't know what I'm doing wrong. Please, help.

Also, can you please point out the loopholes I might have in my concept if it's obvious from my doubt, so I can look up and take care of it?


texts: Why is cyclopropenium aromatic but not cyclodecapentaene?

texts:
An $\ce{sp^2}$ hybridized carbon prefers a bond angle of $120^\ce{o}$. It would be willing to deviate if it acquires extra stability, for example through aromaticity. For this reason, the carbon atoms in cyclopropenium cation are happy with a bond angle of $60^\ce{o}$, which deviates from the standard angle of $120^\ce{o}$ by $60^\ce{o}$.

My question is, why doesn't cyclodecapentaene acquire a planar shape and become aromatic? I am specifically talking about this isomer:

In a regular decagonal structure, each internal angle would be $144^\ce{o}$. This deviates from the standard trigonal angle by $24^\ce{o}$, which is much less than the deviation for the cation.
My guess is that even though the deviation from the standard angle is much lower in the case of cyclodecapentaene, the number of carbon atoms experiencing the strain is far greater. This increases the overall strain in the molecule. Is my thinking correct?


texts: Explain volume contraction in mixtures of alcohol and water

texts: Could someone explain why volume contraction occurs when you mix an alcohol such as ethanol with water in relation hydrogen bonding and the dipole-dipole forces?


texts: It's very confusing that while $\ce{H2SO4}$ has an $n$-factor of 2, whereas $\ce{H3PO3}$ has $n$-factor 2 instead of 3. Many tried explaining it to me by molecular structures, but I don't know how to draw them. Could you please try explaining without the help of molecular structures?


texts: Why is there a mirror image effect in the absorbance and fluorescence spectra?

texts: I've read some answers online but I still can't seem to understand the mirror image effect. Why is the highest energy absorption (v" = 0 to v' = 4) the lowest energy fluorescence (v' = 4 to v" = 0)? Shouldn't the molecule that absorbs the highest-energy light emit the highest-energy light?


texts:
This question regarding appropriate handling of hot concentrated aqueous $\ce{NaOH}$ - with particular concern for avoiding dissolution of borosilicate glassware and contamination of the $\ce{NaOH}$ solution and other reagents - led me to think of two possible solutions:

Coat the glassware with a silane, providing say a polyfluorinated or other inert protective coat
Avoid using glass, choose instead metal or plastic, if possible

Is either of these choices reasonable or common, or is there a better alternative? If so, which is best (considering chemical inertness, safety, complexity (including potentially cost), in that order of priority)?

In the case of choice 2, what commercial sources are there for such labware (for handling hot caustic solution for extended period). A cursory search - eg google and Merck website - did not turn up such products.

Note this question is about relatively small-scale labware (benchtop), not for reactors and the like. Volume max $\pu{5 L}$, $\pu{1 M}$ $\ce{NaOH}$, $\pu{>100^oC}$, exposure time >1 h.


texts: Boiling points of v. similar organic molecules

texts: Given the similarity in formula between pentane ($\small\ce{CH3(CH2)3CH3}$, b.p. 36.2 °C) and neopentane ($\small\ce{C(CH3)4}$, b.p. 9.5 °C), why are their boiling points so different?


texts: Dipole and size of a thioether relative to hydrocarbon

texts:
I am an enzymologist and I would like to check whether the consensus of how enzymes tell thioethers from hydrocarbons on substrates is a fact or fiction.
So are any of these wrong?

S–π interactions are the sole discriminant (in enzymes at least)
They have the same dipole
They are the same size
A thioether and a hydrocarbon have the same angle

From what I can tell...
Point #1 is not really in question: even if it does not account for much, aromatic residues are often found with thiols and thioethers (1/3 of protein have a methione involved in a S–π interaction).
From what I can tell of point #2, 3.55 vs. 3.58 units in electronegativity (ref. wikipedia: electronegativity) won't make a difference. From point #3, while, yes, sulfide is 360 pm and methane is 380 pm (ref. wikipedia: kinetic diameter), but the former is R-S-R, R-CH2-R, so it might be different.

I am not saying they are very different: thialysine (thioether) is a toxic analog of lysine (alkane) and norleucine (alkane) of methionine (thioether; toxic for SAM usage only) due this reason. But nature has evolved to discern similar compounds.

An example, cystathionine (pictured below) is a thioether of cysteine + homoserine or homocysteine + serine (both routes exist) and one enzyme (cystathionine beta-lyase, CβL) can bind the amine on the shorter side, deprotonate the α-carbon and eliminate the thiol (homocysteine) and release the imine (hydrolysed to pyruvate), while a different enzyme (cystathione gamma-lyase, CγL) acts on the other (cysteine and ketobutyrate). The two enzymes do not catalyse both reacts as it would be wasteful (not much just a ATP>AMP). The evolution from one to the other has not be published, but from what I can tell S–π interaction is the driving force. AFAIK, the closest literature to this on cystathionine elimination is my own paper, so I know there is no answer there.


texts: Examples of Lewis base nature of sulfur dioxide

texts: I have read that sulfur dioxide acts as both Lewis base (due to presence of lone pair over $\ce{S}$ and/or $\ce{O})$ and Lewis acid (due to presence of vacant d orbital). I found many examples of $\ce{SO2}$ acting as a Lewis acid (towards $\ce{NMe3},$ $\ce{H2O},$ etc.), but could not find any for its Lewis base behavior. Could someone provide some reactions/equations, please?


texts: What causes the blackening of light bulbs

texts:
in 1878, Thomas Edison (or rather William Joseph Hammer) added an anode in a light bulb in order to catch the flux of electrons coming out from the carbon filament and reduce the phenomenon of blackening of the glass bulb.

However, am I right in saying that this was the wrong course of action? I understand the blackening is due to the accumulation of carbon oxides (such as CO and CO2) produced by the reaction between carbon (and, more recently, tungsten) vapour and the remainder of air present into the glass bulb. Thus, capturing electrons did not solve the problem of blackening (and that is why Edison did not find any use for the extra electrode).


texts: Can a low concentration of an acid disolve solids just as well?

texts:
I'm in the process of removing some hard water stains with vinegar.  It's not working so well.

The stains are in a large fish tank, which I have filled with water and vinegar.  I would expect a lower concentration of acetic acid to cause the acid to dissolve the calcified material slower, but it doesn't seem to be having any effect.

Is there a threshold-like effect on an acid's ability to dissolve such solids, such that a lower concentration would simply be unable to dissolve them (rather than merely dissolving them slower)?


texts:
If oxygen is more electronegative why doesn't it replace chlorine in compounds?

Example:

$\ce{2NaBr + Cl2 -> 2NaCl + Br2}$

works, while

$\ce{4NaCl + O2 -> 2Na2O + 2Cl2}$

doesn't.


texts: What is the distinction between alkyloxy and alkoxy prefixes, if any?

texts: The IUPAC nomenclature guidelines reference alkyloxy and alkoxy prefixes at different points. Is there any distinction, at the level of a principle or rationale, between the use cases for the two? For example, is there an underlying reason why cyclopentyloxybenzene is or isn't preferable to cyclopentoxybenzene?


texts: Why isn't there a third buffering zone in the pH curve of this titration?

texts: I'm in chem 30 right now and we were learning about pH curves and buffering zones. I was looking at a question on the titration of $\ce{H3PO4}$ with $\ce{NaOH}$. The curve showed two qualitative reactions occurring as seen in the two sudden changes in pH. It also showed two buffer zones. Shouldn't there be 3 buffer zones not 2? My understanding is that once the reaction of $\ce{HPO4^{-2}}$ and $\ce{PO4^{-3}}$ is occurring, a third buffer zone would occur.


texts: Molecular term symbols for excited state oxygen

texts: What are the possible term symbols for excited state oxygen with configuration $(1\pi_u)^3$,$(1\pi^*_g)^3$ (all other occupied orbitals are closed shell)? Based on the possible values of S and $\lambda$ it seems that $^1\Delta_u$, $^3\Delta_u$, $^1\Sigma_u$ and $^3\Sigma_u$ are possible. However, I am not sure in this case how to determine the +/- labels for the $\Sigma$ term symbols. For ground state oxygen, triplet states pair with - and singlet states with + to give overall antisymmetric wavefunctions. However, in this case, two different orbitals are involved, so does this rule no longer apply?


texts: What is the substance with the highest specific heat?

texts: I always learned that water has the highest specific heat, but I recently saw that Hydrogen has a specific heat as high as 14 cal/gC and helium has a specific heat of 5 cal/gC, which would be much higher than water? Is this true? and how can it be if there are so many "proofs" in nature , showing that water has the highest specific heat?


texts: Why does steel wool catch fire when rubbed with a battery?

texts: I was watching an episode of Man vs Wild where steel wool was rubbed with phone battery. To my surprise, the wool caught fire. What is the reason for this?


texts: An alternate purification process for sugar separation form bee honey?

texts:
Bee honey contains 75% sugars (Fructose, Glucose, Maltose, Sucrose and others), some water and low amount of different compounds (up to 5%) Wiki.

Basic purification is done by addition of phosphoric acid and calcium hydroxide to form calcium phosphate which is afterwards removed (after precipitation). Then is filtered through activated carbon or ion-exchange resin Sugar refinery.

I am looking for a separation process, that can separate the sugars. Is there any other technique or process for removing the rest form the sugars, e.g. some electrochemical separation? First idea would be chromatography, but I would like to separate kilogram(s) of bee honey.


texts: Why Isodecane (B.P.: 327 *C) has a higher boiling point than decane (B.P.: 174.1 *C)?

texts: Branched chain molecules have lower boiling point than straight chain molecules because branched chain molecules have a smaller surface area where they can be attracted by other molecules. Then, why Isodecane (a branched chain molecule) has a higher boiling point than Decane (a straight chain molecule)?


texts: Why do we neglect the protons from water's autoprotolysis?

texts:
Why don't we need to consider the $\ce{H+}$ ions of water when finding the $\ce{pH}$ of $0.01~\mathrm{M}$ of $\ce{HCl}$ solution?

The $\ce{pH}$ value of something is depending on the molarity of $\ce{H+}$ ions. But the teachers says the calculation is just $-\log(0.01)$, don't we need to consider the $\ce{H+}$ ions of water?


texts: Electrolytes in electrochemical half cells

texts: In most of the examples in my book I have come across, the electrolyte for an electrochemical half cell has always been the aqueous version of the metal used. For example, a silver electrode is immersed in a silver solution and so on, but is why is this necessary? Surely any positive metal ion will do?


texts: How do I convert salinity measured in mg/L Cl into parts per thousand as NaCl?

texts:
I have collected water data using a refractometer that records salinity in ‰ (parts per thousand) as $\ce{NaCl}$. I want to compare my data to other data but every journal article I read  has the results in $\pu{mg/L }\ce{Cl-}$

How do I convert my $\pu{ppt}$ data into $\pu{mg/L}$ or vice versa so I am comparing apples to apples?


texts: Among the halogens, why is it that the fluorine has the lowest bond dissociation enthalpy, considering the fact that fluorine is the smallest and the internuclear distance between the fluorine molecule is least and $2p-2p$ overlap should also very very strong ,the bond dissociation enthalpy should have been very high but it is lowest among the halogens. Why is it so??


texts: Compressibility factor (Z) of a real gas

texts:
I was wondering whether the compressibility factor of a real gas (given by $Z = V_{\mathrm{real}}/V_{\mathrm{ideal}}$) is supposed to be measured while keeping pressure constant?
I was attempting to answer the question below and got stumped at part (iii) because I had trouble finding out which was the dominating force being that when I tried calculating the compression factor I got a value of 1 (because $V_{\mathrm{real}}$ and $V_{\mathrm{ideal}}$ are the same, but the pressures are significantly different).

3.0 mol $\ce{CO2}$ behaving as a van der Waals gas, when it is confined under the following conditions: at 750 K in $\pu{150 cm^3}$. For $\ce{CO2}$ van der Waals coefficients, a: $\pu{3.610 atm L^{2} mol^{-2}}$, b: $\pu{4.29 \times 10^{-2} Lmol^{-1}}$. The universal gas constant R is $\pu{8.206 * 10^{-2} L atm K^{-1}mol^{-1}}$
i) Calculate the gas pressure (in atm), [5]
ii) What is the molar volume of the gas (in L/mol), [1]
iii) What is the pressure when it is ideal gas and use it to state the dominating force in the above gas?


texts: Calculation of total pressure given ratio of pressure equilibrium constants

texts:
The equilibrium constants $K_{\mathrm{p},1}$ and $K_{\mathrm{p},2}$ for the reactions $\ce{X(g) <=> 2 Y(g)}$ and $\ce{Z(g) <=> P(g) + Q(g)}$, respectively, are in the ratio of $1:9$. If the degree of dissociation of $\ce{X}$ and $\ce{Z}$ are equal then the ratio of total pressure at these equilibria are?

My Approach: Let the degree of dissociation be $\alpha$

So $K_\mathrm{c,1}$ for the first reaction is
$K_\mathrm{c,1} = \frac{(2\alpha)^2}{1+\alpha}$

Similarly, $Kc_2$ for the second reaction is $K_\mathrm{c,2} = \frac{(\alpha)(\alpha)}{1+\alpha}$

I don't know how to proceed from here and relate these to the ratio of $K_{\mathrm{p},1}$ and $K_{\mathrm{p},2}$. I need help here.


texts:
let’s take an example: if we have a glove-box filled with helium at 5 bars at room temperature which is far beyond its critical point, what actually it would be like ?
would it be like a normal gas ? would it be like a liquid ? or it will be like a condensed vapors ? can this supercritical fluid dissolve salts for example ? would it quench hot metals like water ?
if I put may hands inside this fluid would it feels like putting my hands inside a water ? or it feel like a normal air ?

is supercritical fluid a special types of a liquid ? if no, why then some SCFs used as a solvent ?

I searched a lot but really can’t find any clear answer explains what they ar exactly.

Note: this is not duplicate, I asking about the nature of SCFs while the "duplicated" question was asking about room temperature SCFs which is clearly different.


texts: What limits supersaturation in the absence of nucleation sites?

texts:
Imagine a scenario where we have a chamber with air that is supersaturated with water vapour. In this ideal scenario there are no nucleation sites (e.g no suspended particles or nucleation on the walls of the chamber).
What is the physical/chemical mechanism that limits further supersaturation?


texts:
What mass of copper, originally at $50\ ^{\circ}\text{C}$ must be added to $1\ \mathrm{kg}$ of $10\ ^{\circ}\text{C}$ water to raise the water temperature by $10\ ^{\circ}\text{C}$?

We can work out that the necessary energy gain by the water is $41.8\ \mathrm{kJ}$, but I'm not sure how to work out the mass of copper, since both the mass and the temperature change is unknown in the equation $\Delta E=mc\Delta T$? Or do we assume that the copper cools to $20\ ^{\circ}\text{C}$ also?


texts: How do I calculate lattice points per unit volume?

texts:
My professor was explaining simple cubic, body centered cubic, and face centered cubic lattices and I didn't quite understand the calculations below:

Simple Cubic: $8 \cdot 1/8 = 1$ lattice point per unit volume
Body Centered Cubic: $(8 \cdot 1/8) + 1 = 2$ lattice points per unit volume
Face Centered Cubic: $(8 \cdot 1/8) + (6 \cdot 1/2) = 4$ lattice points per unit volume

Can someone explain the reasoning behind these values in the equations?


texts: Does the salt bridge in galvanic cells resemble the ATP pump in the inner mitochondrial membrane? And if yes than did someone use this pH difference in harvesting this energy?


texts: A theoretical chemistry question about elements and their presence over time

texts:
I'm not a chemist myself, but I can't think of a better place to get some insight about elements and chemistry than from people who live and breathe it here on stackexchange. This is not any kind of homework problem just my personal curiosity, and I'd appreciate any input you might have on it.
Imagine we are travelling back in time towards the big bang. Universes being pulled back together, the density of energy is larger, atoms still have their neutral state but energy is colliding at a much higher frequency.
Is it possible that in these times, the amount of energy would permit atoms larger than we have observed in nature or been able to create in the lab?
If we then travelled to a far future, hundreds of millions of years from now, when the energy of the universe is much more spread out, and atoms have had more time to decay and lose electrons, wouldn't there be, at some point, a time where we no longer observe certain heavier elements in nature?
At either of these points in time wouldn't you expect to find more ionic elements in nature?


texts: Flory–Schulz type distribution with stoichiometric imbalance

texts:
In a typical step-growth polymerization, the Anderson–Schulz–Flory distribution is the probability mass function that describes the number fraction or weight fraction of polymers of length $x$ at a given extent of reaction $p$.  The extent of reaction, $p$, is a value between 0 and 1, and $x$ is the degree of polymerization for any given oligomer or polymer present in the system.

$$\begin{align}
\text{mass fraction} &= p^{x-1} \cdot (p-1)^2 \\
\text{weight fraction} &= x \cdot p^{x-1} \cdot (p-1)^2
\end{align}$$

A nice derivation of these equations can be found in this video.  Figure 1 illustrates a plot of the number fraction distribution as a function of the degree of polymerization for several extent of reactions.  Figure 2 illustrates the plot of the weight fraction distribution as a function of the degree of polymerization for several extent of reactions.

Note that high extents of reaction in step-growth polymerizations result in very broad distributions, and are also required for high molecular weight polymers.
Carothers' equation describes how stoichiometric imbalances necessarily limit the possible degree of polymerization:

$$x_\text{average} = \frac{1+r}{1 + r - 2rp}$$

where $x_\text{average}$ is the average degree of polymerization, $p$ is the extent of reaction, and $r$ is the mole fraction of the reacting functional groups. $r$ is always a number between 0 and 1.  The excess functional group is always taken to be in the denominator. When $r$ is equal to 1, stoichiometric balance exists, and the equation reduces to:

$$x_\text{average} = \frac{1}{1-p}$$

For example, if I react a diol and a diacid under step-growth conditions:

My goal is to purposely limit the degree of polymerization of a chemical reaction by introducing a stoichiometric imbalance in order to form short chain oligomers.  I'd like to predict/calculate the statistical distribution of molecular weights for a given extent of reaction, p and stoichiometric imbalance, r.

I'm having trouble convincing myself that the Flory–Schulz distribution is appropriate for modeling step-growth systems that contain stoichiometric imbalances. Is there a straightforward way to incorporate stoichiometric imbalance into these distribution functions? Any help would be appreciated.


texts: Why does a smaller bandgap correlate to increased absorption of visible light?

texts: I am currently involved in a project on metal organic frameworks in my AP chemistry class, and specifically their applications in $\ce{CO2}$ reduction into formate. All the explanations we can find on why a smaller bandgap correlates to higher absorption and quantum yields refers to PhD-level chemistry, e.g. the Density Functional Theory. Can someone provide a simplified version of this?


texts: Infrared absorption spectrum of primary amides?

texts: It's my understanding that the infrared absorption spectrum of primary amides beyond having a broad peak also has 2 sharp peaks representing the symmetric and antisymmetric stretch. My question is why isn't there a third peak representing a bending motion where the two hydrogen molecules bend towards each other?


texts: Why is the electrode potential for a cathode positive?

texts:
Electrode potential is the potential difference between the electrode and the surrounding electrolyte.
If the potential of the cathode is positive this means that the potential of the electrode is greater than the potential of the electrolyte, which means that the electrons will flow from the electrolyte to the cathode.
Shouldn't it be the other way around? shouldn't electrons flow from the cathode to electrolyte meaning the electrode potential should be negative?
Similarly, we can say that the electrode potential for an anode is positive.
Can someone point out the faults in this reasoning?


texts: Why can't HS- participate in E1 reactions?

texts: In my textbook (Organic Chemistry by Klein), it says that certain molecules can only act as nucleophiles and not as bases; thus they can only undergo substitution reactions, not elimination reactions. This group of molecules includes: $\ce{Cl- , Br- , I- , HS- , H2S , RS- , RSH}$. I know that while E2 reactions require strong bases, E1 reactions do not. Even a base like $\ce{H2O}$, which is pretty weak, can undergo E1 reactions. Then why can't something like $\ce{HS-}$ undergo a E1 reaction? For example, if we have a tertiary alkyl halide and $\ce{HS-}$, I would expect a mix of $S_N1$ and E1 products. However, my book claims there are only $S_N1$ products. Why is this the case?


texts: SN1 products for (1S,2R,4R)-1-chloro-2,4-dimethylcyclohexane

texts:
Question

Total number of SN1 products of given compound are
A) $3$
B) $4$
C) $5$
D) $6$

Answer

 (C) $5$

My attempt
I can find only $4$ products. The two stereoisomers formed from the carbocation, when chlorine leaves, and two stereoisomers formed when the hydrogen from the neighbouring carbon centre migrates (i.e. rearrangement occurs) and nucleophilic attack takes place from both sides.
I still am unable to find the fifth product. Moreover, I don't suppose the $\ce{-CH3}$ opposite to the point where the carbocation forms can interfere with the product. What would be the fifth product?


texts:
While studying dipole moment in organic chemistry, I got stuck at a particular statement written in the book :

  Symmetrical molecules without lone pairs of electrons will have $\mu = 0.$

The main problem was, why would they have $\mu =0$ ?

What type of Symmetrical molecules are possible?

The book gave the example of $\ce{BH3}$. How is this a symmetrical molecule?


texts:
The definition of phase :
Uniform chemical and physical composition.

So Alpha iron (0.001% carbon) and alpha iron (0.002% carbon)  are two different phases??


texts: In ESI-MS, why do we assume that the positive charge on the analyte must come from protonation from the solvent?

texts: In ESI-MS, we ionise the molecules using a high voltage. Why wouldn't this high voltage cause the ejection of an electron from the analyte itself, generating a M+ ion. Why do we have to assume the the positive charge comes from protonation of solvent molecules?


texts: What is the most common oxidation state of gold?

texts:
I had a test this morning which had the following question:

  What is the most common oxidation state for gold?
  (a) +1  (b) -1  (c) +2  (d) +3

Since the electronic configuration of $\ce{Au}$ is $\ce{[Xe] 4f^{14} 5d^10 6s^1}$. After removing the $\ce{6s^1}$ electron and gaining $+1$ charge, $\ce{Au}$ should have noble gas configuration and hence this should be the most stable configuration. So the answer has to be +1.
Could someone verify my reasoning?


texts: MO theory used in organic chemistry textbook

texts:
I'm currently using Clayden's organic chemistry textbook, and when he shows MO diagrams of functional groups of organic molecules, he sometimes treated it as if only orbitals on two atoms are interacting. For example, the carbonyl chemistry is reduced to looking at the interaction between C and O orbitals. (For conjugated systems the MO diagrams he created make more sense to me)

However, as far as I know, MO theory is used to construct wavefunctions that spread over the whole molecule. Hence, how is it justified that we are combining orbitals centered on a pair of atom rather than all atoms in the molecule? What is that powerful assumption that allows us to apply MO theory locally at functional groups?


texts: How do i make an molecular orbital diagram step by step?

texts: My professor explained me, but i'm still unable to do a correct molecular orbital, for a diatomic molecule


texts: Are there computer searches for new theoretical minerals in a similar vein to Folding@Home or SETI@Home?

texts:
As a surprise gift to a friend I would like to discover a new theoretical mineral and have it named after them. I have some understanding that not all minerals have been discovered, and some minerals exist in theory but have not been found on earth.

Is there a computer search that looks for new minerals? Would it be difficult to write one, if one does not exist?


texts: How to find out oxidation state when compound has multiple electronegativities

texts: How do I solve for oxidation state in something like CH3-O-F? The fluorine is more electronegative than the oxygen which is more electronegative than the carbon which is more electronegative than the hydrogen. In this case would everything except the fluorine be oxidized?


texts: Least likely product of a hydrocarbon cracking reaction?

texts:
The hydrocarbon $\ce{C17H36}$ can be cracked. Which compound is the least likely to be produced in this reaction?
A: $\ce{C3H8}$ B: $\ce{C4H8}$ C: $\ce{C8H16}$ D: $\ce{C16H34}$

Is it D because cracking's purpose is the breaking of long hydrocarbon chains into smaller ones?


texts: Comparison of standard reducing potential of Co3+ and Mn3+

texts:
$\ce{Co^3+(aq) + e- → Co^2+(aq)}$   +1.81 V

$\ce{Mn^3+(aq) + e- → Mn^2+(aq)}$ +1.51 V

This is the data of Standard reducing potentials I have found on internet. Why is reducing potential of $\ce{Mn^3+}$ is less than that of $\ce{Co^3+}$. $\ce{Mn^3+}$ converts to $\ce{Mn^2+}$ which is half filled configuration and hence more stable. Am I missing something?


texts: Sugar burning with the assistance of ash

texts: If a plain pile of sugar (or a sugar cube) is heated with a torch, it just melts and gives off smoke. However, if some paper or wood ashes are added, it burns quite easily. What are the ingredients of the wood ash that allow this to happen? If I just used sodium carbonate instead of wood ash, would it work as well?


texts: Is thin layer chromatography suitable to characterize distillate samples?

texts:
Would I be correct if I state: Thin layer chromatography (TLC) is a separation method for non-volatile mixtures. Because distillate samples are pure, this would not be appropriate.

I'm unsure and would like some insight into this.


texts: Seperating out iron from ferrous sulfate

texts: I don't need to necessarily seperate pure iron, but from a ferrous sulfate solution, I am trying to form a precipitate with iron. By getting a precipitation of an iron compound, I can find out the amount of iron in the solution. Any help would be appreciated. I'm completely new and tried finding information online but all of it was beyond my comprehension. I apologise for my ignorance, but help would really be great.


texts:
Chemical elements are typeset with upright font ($\ce{H2O}$ for water) while variables are typeset with an italic font ($V$ for volume).

But is there a convention what to do with multi-letter variables like IC50, EC50 (or others without subscripts)? Is there any official convention for this?

Special cases may be pH and pOH where on could read p as an operator and H and OH as chemical abbreviations, so I would always write them upright. But I am not sure about the others.


texts: Mechanism Permitting Proton Sponge Effect

texts:
The proton sponge effect is utilized as a drug delivery method to release contents packaged in micelles (usually coated in PEG or another protective polymer) into the cytoplasm of a cell after being endocytosed.

The micelle is able to attract hydrogen ions (which attracts chloride ions) into the endosome, decreasing the internal pH of the endosome. Water also follows the inward flow of ions and causes the endosome to burst, releasing micelle and contents into the cell.

I am wondering how ions are able to cross the endosome lipid membrane in order to attract water molecules and create swelling. I am aware that endosomes may have membrane bound hydrogen ATPases, but this doesn't explain chloride entry.


texts: Solvent leveling means that strong acids completely dissociate in that solvent so it is impossible to distinguish between two acids that completely dissociate in it. A solvent levels and acid if the $K_\text{a}$ of that acid is greater than 1. However, that’s not completely dissociated. An acid can have a $K_\text{a}$ of 2, 3 or 25 what’s the problem with being able to distinguish between them? In truth, whatever the $K_\text{a}$ it’s not actually COMPLETELY dissociated.


texts: How would I write an input Lammps command for continuous change in temperature?

texts: I'm going to study the thermal expansion of graphite. For this goal, I should change the temperature continuously. But I do not know how to code it by Lammps?


texts:
Higher the positive oxidation state of the central atom, more will be its polarising power which, in turn, increases the covalent character of bond formed between the central atom and the other atom.

This seems counter-intuitive to me. When the polarising power of the central atom increases, shouldn't the bond be more ionic instead of covalent? If not, can you tell me where I am wrong?


texts: Explain the difference between reaction intermediate and reactive intermediate

texts:
Wikipedia definitions of the terms:

Reaction intermediate:

https://en.m.wikipedia.org/wiki/Reaction_intermediate

Reactive intermediate:

https://en.m.wikipedia.org/wiki/Reactive_intermediate

What I don't really understand :

Are they defined just based on their stability?

What I mean is that, if an intermediate is stable is it reaction intermediate and if unstable is it reactive intermediate?

(Or) is there any deeper difference between them?...After reading the entire page I have an intuitive feeling that there is more to them than just stability.


texts: How do Electrons Cross Nodes in Orbitals?

texts:
I was wondering in orbitals that have nodes such as the p orbital, how does the electron move from one lobe to the other? I know that people say it is because of the wave/particle nature of electrons but they don't actually explain how they travel across the node without actually passing it.

My teacher says it is because that electrons are able to act like waves and hence like how EM waves can pass through a wall, electrons are able to pass through the node. However when he says that electrons are like a wave, does he mean that it is literally a wave so does an electron have a wavelength, amplitude, frequency, etc? Because I remember reading somewhere which stated that electrons aren't literally like waves. However they can be mathematically described using concepts that apply to waves. Is this true?

From the comments, they state that electrons can be thought as standing waves. After looking at the internet I came across the following image which explained how electrons act as a standing wave:

However this doesn't make sense to me. Don't electrons exist in orbitals not in orbits around the nucleus? If so, isn't this wrong? Also, since electrons move in orbitals, how can there be any end points as it can move anywhere and its movement isn't restricted to a close loop. Hence how can it act as a standing wave?


texts: Why is the boiling point of homologous primary > secondary > tertiary alcohols whilst their solubility in water is the reverse?

texts:
From my understanding, for homologous alcohols, primary alcohols have the highest boiling points, because the OH group is the most accessible for other molecules to hydrogen bond to, therefore stronger intermolecular forces result in higher mp/bp.

One the other hand tertiary alcohols have the highest solubility in water because the packed structure of branches means the non-polar part of the molecule is condensed and therefore water near any part of the molecule can receive these hydrogen bonds. Doesn't this mean tertiary alcohols have the most accessible hydrogen bonds and therefore should have the highest melting point too?

Alternatively does this have to do with water being small and alcohols being larger therefore 'access' requirements to hydrogen bonding are different as larger alcohols need to be even closer than water to make a difference therefore the packing is less relevant as even being slightly away from the molecule means failure to access hydrogen bonds but water will be ok with being slightly away.


texts:
Also good against fungi, amoeba, and enveloped viruses,[7] quats are believed to act by disrupting the cell membrane.

Quaternary ammonium cleaners have long-alkyl substituent chains. Why is this so?

Does this have anything do with increasing the ability of the cleaners to penetrate the phospholipid bilayer, which has its non-polar portion oriented outward and its polar phosphate backbone oriented inside the cell? Does the alkyl portion dissolve into the lipid bilayer and wreck havoc?

What is the exact mechanism?


texts: Potential energy expectation value and virial theorem

texts:
I have been trying to solve this problem

Part a) can be proved using the formula .
For part b), the expectation value of the potential energy can be calculated from the integral
,
where

Therefore, the integral to be solved is

which gets simplified using spherical polar coordinates into

However, I have seen that the expectation value for the potential energy should be

Obtained using the same integral that I used, but using this expression for the wavefunction

which, from my understanding, should be the same expression but not in atomic units.
I am not familiar with conversions using atomic units, Bohr radius, Hartree, and so on. So I am not sure if what I have done is correct or if there's something missing.
For part c), using the virial theorem, the expectation value of the kinetic energy is
[T] = [E] - [V] = -0.5 - [V]
I am also confused by the Hamiltonian and the Laplacian which I did not use in my solution, am I missing something?
If I am not being clear please let me know and I will try to explain myself better.
Thanks very much to whoever is willing to help me understand this problem better!


texts: In the simplest terms, what is exchange current density?

texts:
what is exchange current density, and ideally how does it relate to overpotential

I know it's related to the amount of dynamics in a reaction, so it can tell us how simple or complex a reaction mechanism is, but I don't have a clear idea of what exactly it means


texts: Relationship between the ideal gas constant and entropy

texts: So it dawned on me the other day that the ideal gas constant $$R = \pu{8.31 J mol-1 K-1}$$ has the same units as molar entropy. Is there some deeper meaning behind this or is it just a coincidence that this occurs?


texts: Is it possible for three carbon double bonds to form next to each other in a carbon chain?

texts: In a typical carbon double bond $sp^2$ hybidrization is used to explain the resulting bond. When two carbon atoms A and B form a double bond one $sp^2$ orbital from A bonds to another $sp^2$ orbital from B and one $p$ orbital from A bonds to a $p$ orbital from B. This leaves two $sp$ orbitals sticking out the end of the ethene-like molecule. I think one could stick two ethene-like molecules end to end to stick together with two $sp^2$ orbitals from each end but then I think one would have an interfering $p$ orbital that would subtract and leave a bond order of 1. I think one might then have further hybridization and end up with three 1.67 bonds (instead of one single and two double bonds) but not three double bonds. The second possibility is sticking together two $sp^2$ orbitals and one $p$ orbital from A to two $sp^2$ orbitals and one $p$ orbital from B leaving behind one $sp^2$ bond sticking out on each end. I think one could stick together such pair with another pair rotated at an angle. After hybridization I think one ends up with three net 2 bonds together but this is confusing to me. A third possibility is sticking together two ethyne-like molecules together but I think that would be a hybrid of two 3-bonds and a -1 bond which would be 1.67 again.


texts: How to find out the value of 'n' in the equation (ΔG = −nFE)?

texts:
I can figure out the value of 'n' in simple equations like
Fe³⁺ + e⁻ → Fe²⁺ (which would be n=1 here.)

But in equations like 2Cu⁺→ Cu²⁺ + Cu, I can't figure it out. I assumed the value of n would be 2 here as two electrons are involved in the disproportionation reaction, but my book says n=1 here. Can anyone help me understand what is the value of 'n' in this equation? Thank you.


texts: Why is AlF3 soluble in anhydrous HF only in the presence of KF?

texts:
I am pondering over that what must be the reason that $\ce{AlF3}$ is insoluble or less soluble in anhydrous $\ce{HF}$? And pageants it is soluble to a good extent only in the presence of $\ce{KF}$? Is there any other reagent in presence of which $\ce{AlF3}$ is soluble in $\ce{HF}$?

I guess a probable answer for the cause of insolubility could be:
"the nonavailability of $\ce{F-}$ ions because of the presence of intermolecular hydrogen bonding in $\ce{HF}$, which makes $\ce{AlF3}$ insoluble in $\ce{HF}$."

  Can someone elaborate the cause and mention other such reagents like $\ce{KF}$ which can be used for the same purpose?


texts: When we cannot use Friedel-Crafts acylation to insert alkyl group?

texts:
Questions:

Show a probable synthethic pathway to obtain the first molecule, I.
Will the same strategy be used to insert the alkyl group for J. Explain.

My answers (please tell me if there is any incorrect answer):

Friedel-Crafts acylation -> Clemmenson reduction -> Nitration -> Reduction of Nitro Benzene

No, to insert alkyl group for molecule J, it must undergo Friedel-Crafts alkylation. In Friedel-Crafts alkylation, there is carbocation rearrangement to ensure the carbocation is stable and tertiary. In J, the carbon that will directly attach to benzene is already stable, so the C(CH3)3 substituent will attach directly to benzene. (I'm not sure what to explain more)

Is this correct for alkylation step in J?

My questions:

For no. 2, is it true if we say that, in this case, no rearrangement will occur in Friedel-Crafts Alkylation step because the carbocation is tertiary and stable so it can proceed with this step (Friedel-Crafts Alkylation). Is it possible that rearrangement will not occur in Friedel-Crafts Alkylation?
Why we cannot use Friedel-Crafts acylation to insert alkyl group in J? I am confused, if we use (CH3)3Cl, there will be no carbocation rearrangement, but why the question asked about acylation, I think it is not possible to undergo acylation step because there is no carbocation rearrangement, so the substituent attached to J will be CH3CH2CH2???


texts: Effect of phenyl and vinyl substituents on Acidity of carboxylic

texts:
Recently I came across this statement in my textbook:

  Direct attachment of groups such as phenyl or vinyl to the carboxylic
  acid, increases the acidity of corresponding carboxylic acid contrary
  to the decrease expected due to resonance effect.

On researching online, I found this statement as an answer:

  Although we expect a decrease in acidity due to the resonance effect
  of phenyl and vinyl groups, but because of the greater
  electronegativity of the the $\ce{sp^2}$ hybridized carbon which is
  directly attached to the carboxylic carbon.

My Thoughts

Please keep in mind that the carbonyl carbon(here carboxylic carbon) is also $\ce{sp^2}$ hybridized. So $\ce{sp^2}$ hybridized carbon is directly attached to the carboxylic carbon. Therefore there is no electronegativity difference between the two carbons and as a result of this only +R effect should work and direct attachment of groups such as phenyl or vinyl to the carboxylic acid should not increase the acidity of corresponding carboxylic acid rather they should decrease its acidity due destabilization (due to electron donating nature vinyl and phenyl group by means of resonance) of conjugate base so formed.

The question

Kindly explain it theoretically by giving plausible reasons as to why the statement in my textbook is true?

Note: avoid quoting pKa values


texts: How to create .CIF file from DRX data in a paper, for compound not found in crystallographic database

texts:
I tried to recover a .CIF file with the crystal structure for the compound discussed in this 2006 paper, strontium hydroxide octahydrate - $\ce{Sr(OH)2·8H2O}$ - from Cambridge Crystallographic Data Centre (CCDC), but couldn't find it. The paper itself has tables with information recovered from x-ray diffraction data, as shown below.

Is there any free software or open source tool where I can just type the data from these tables to assemble a crystal structure like the ones I'm used to download from the database?


texts: How to prove at what pH the color of an indicator will change based on its pKa?

texts:
The equivalence point of an acid-base titration can be determined by choosing the appropriate colored indicator. This indicator is a weak acid $\ce{HA}$. The undissociated acid has a different color than it's ion $\ce{A-}$. The $\mathrm{p}K_\mathrm{a}$ value of a colored indicator is given to be $\mathrm{p}K_\mathrm{a}=6$. At what value of the $\mathrm{pH}$  will the color change? Please explain your answer. (Assume that both colors are equally well recognizable).

I've had this question on an exam and I can't seem to figure out what exactly the answer could be.

I would intuitively say that the color change happens at $\mathrm{pH}=6$. If the $\mathrm{pH}$ is lower than 6 then there are less $\ce{A-}$ ions and more $\ce{HA}$ (acid-indicator) in the solution. Hence the solution will take on the color of the undissociated acid-indicator. If the pH is higher than 6 then the $\ce{HA}$ starts to dissociate more to $\ce{H3O+}$ hence there being a higher $\ce{A-}$ concentration and the solution takes the color of the indicator's conjugate base. But I'm not sure if my thought process is right or how to 'prove' it's right.


texts: Mass transfert in process chemistry engineering, two film theory

texts:
I'm having troubles to understand a part of my lesson. I have no idea where to ask my question, but it is consider as chemistry so here we go.

Let me introduce some notations :
$x$ and $y$ are the mole fractions
of the same compound but respectively in liquid phase and in gas
phase.
$k_{c_l}$ and $k_{c_g}$ are the coefficient of exchange of matter in
$\ce{m.s^{-1}}$
$N_{1n}$ is the molar flux density of the compound $1$ in the normal position

Let now me introduce (translating from french to english) you the part of the lessons in which I have troubles :
No phenomenas of production or consommation of the compound $1$ occur in the interface $I$, and we are in stationnary state then the molar flux density is the same in both parts and we have $$N_{1n}=c_lk_{c_l}\left(x_1^{I}-x_1\right)=c_gk_{c_g}\left(y_1-y_1^{I}\right)$$
The fluids at the interface are supposed to be in thermodynamical equilibrum then we have $$y_1^I=K_1^{eq}x_1^I$$

We can for example define a fictive gas phase which will be in equilibrium with the liquid phase (or the contrary). The mole fraction of the compound $1$ is by definition $$y_1^*=K_1^{eq}x_1$$
The total driving force is then $$\begin{align} (y_1-y_1^*)&=(y_1-y_1^I)+(y_1^I-y_1^*)\\ &=(y_1-y_1^I)+ K_1^{eq}\left(x_1^I-x_1\right)\end{align}$$ if we suppose to have a unique average equilibrum constant in the liquid film.
Now I'm having troubles their :
We can then define a global transfer constant in the ralation to the driving force in gas phase : $$\frac{N_{1n}}{K_{c_g}c_g}=\frac{N_{1n}}{k_{c_g}c_g}+\frac{N_{1n}K_1^{eq}}{k_{c_l}c_l}$$
I really don't understand this last relation, if someone can help me, I would be glad. I apologize in advance for the troubles you can have too, to understand what I tried to translate here.
Thank you
PS : I have really no idea for the tags, feel free to edit them


texts: Can a Flame Ionization Detector be used with H2 as carrier gas?

texts:
In a Gas Chromatography instrument can a Flame Ionization Detector be used with $\ce{H2}$ as carrier gas?

My intuition says no, because I'd be afraid you'd set the whole column on fire (or worse).

Is this right? Or can an FID be used even with $\ce{H2}$ carrier gas safely?


texts: Should I use specific heat to calculate how much fuel is required?

texts:
Question:

  A backpacker wants to carry enough fuel to heat $\pu{3.0 kg}$ of water from $\pu{20 ^\circ C}$ to $\pu{100.0 ^\circ C}$. If the fuel he carries produces $\pu{36 kJ}$ of heat per gram when it burns, how much fuel should he carry? (For the sake of simplicity, assume that the transfer of heat is $100\%$ efficient.)

My hunch is that it involves the specific heat equation $Q_\mathrm p = m  c_\mathrm p  \Delta T$ where $Q$ is heat, $m$ is mass, $c_\mathrm p$ is the specific heat capacity (in this case $\pu{4.184 J/(g ^\circ C)}$) under constant pressure and $\Delta T$, but twice I calculated the wrong answer, and would like a more intuitive understanding of the problem.


texts: Complexes formed by lanthanides and actinides

texts:
A very simple test for the presence of alcohols in the lab involves adding ceric(IV) ammonium nitrate solution which gives a pinkish red colour in the presence of alcohol.

When I looked up the structure of this compound it turns out to be quite interesting. So a couple of questions about lanthanides came up in my mind (a Google search only comes up with very complicated research papers):

Wouldn't this compound be highly unstable since there 12 donor atoms (forming an icosahedral structure) surrounding it (but it is quite stable)?
Is the formation of complexes in lanthanides and actinides similar to that of transition metals? Do $\ce{f}$ orbitals undergo crystal field splitting just like $\ce{d}$ orbitals?
Are higher coordination numbers like 12 more common (than octahedral and tetrahedral structures) among lanthanides and actinides because they have more orbitals for bonding, or is this compound an exception?


texts: Some abnormalities in the Periodic Table

texts:
I observe some elements like $\ce{Cr}$ and $\ce{Cu}$. Some of them have strange oxidation numbers that don't really fit the purpose of making the element as stable as possible. Just Chromium, for example, it has one valence electron in 4s, the oxidation tells that it is gonna lose 2 electrons. Which obviously breaks the stability of half filled 3p orbitals.

If this can be explained by the fact that $\ce{Cr}$ has weak electronegativity, then what about $\ce{Cu}$? It is among the most electronegative transition metals, but still might lose two electrons despite having fully filled 4d orbitals.


texts: Are there any databases with rate constants for keto-enol tautomerism in small molecules? I'm looking for rate constants if possible.


texts: Quantitative determination of chemical composition of a simple unknown mixture

texts:
Unknown mixture A [$\ce{H2SO4}$ and $\ce{CuSO4}$]
Unknown mixture B [$\ce{H2SO4}$ and $\ce{HNO3}$] (ranged between $\pu{0.1 - 0.3 M}$ for the solution)

(E.g. if you are using Unknown mixture B [$\ce{H2SO4}$ and $\ce{HNO3}$], concentration of $\ce{H2SO4}$ will be $\pu{0.1 – 0.3 mol/dm3}$, and concentration of $\ce{HNO3}$ will be $\pu{0.1 – 0.3 mol/dm3}$.)

Sodium hydroxide [$\ce{NaOH}$] solution (approximately 2.0 M 1.0M)
Potassium hydrogen phthalate [$\ce{C8H5KO4}$] powder
Barium chloride [$\ce{BaCl2}$] solution ($\pu{0.3 M}$)
Copper sulfate pentahydrate [$\ce{CuSO4.5H2O}$] powder

You may choose to use spectrophotometric, titrimetric, or gravimetric methods to execute your analysis. There are no major restrictions apart from non-wasteful use of chemical reagents.

How do I approach this?
I tend to use the gravimetric method to perform crystallization of anhydrous copper sulfate so I can measure the mass of $\ce{CuSO4}$ in Mixture A, but for this experiment I will need $\ce{(NH4)2SO4}$, which not provided.
Using spectrophotometry, I will be able to find the concentration of $\ce{CuSO4}$ in the mixture as copper sulfate pentahydrate ($\ce{CuSO4.5H2O}$) powder is given, and I can make a blank out of the chemical is it true?


texts:
In the picture attached here, is the compound in water soluble or insoluble?

I get confused while identifying solubility of a solute in a solvent when a situation like this arrises. The crystals of the solid have become liquid, but they give a certain transluscent white colour to the solvent (water in this case). So in this picture, is the solute soluble in water?


texts: Why are regular plastic bags not smell-proof?

texts:
Due to the wide use of plastic bags as containers for almost everything in everyday life, I naturally use them to wrap and hold dirty diapers as a temporary stop before getting to throw them in the garbage outside. However, these bags do not stop the smell from spreading around the bags at all.

I wonder why is that? These bags seem to be tight enough to hold liquids (when intact), but they do not hold smells at all. I guess the obvious answer is that the plastic\nylon polymers have wide enough gaps between them for the passage of small clusters of molecules in the micro- or nano-level, but I was wondering if there was some other explanation and if anyone could elaborate on the matter.


texts: Finding partial pressure of a gas in a mixture

texts:
A mixture of argon and carbon dioxide was initially at a total pressure of $\pu{1.72 atm}$ in a volume of $\pu{1.72 L}$ at $\pu{17 ^\circ C}$. The carbon dioxide was then completely removed from the mixture by passing it through a solution of sodium hydroxide ($\ce{NaOH}$). The argon was collected in a $\pu{1.1 L}$ vessel and its pressure found to be $\pu{1.55 atm}$ at a temperature of $\pu{28 ^\circ C}$. What was the partial pressure of carbon dioxide in the original gas mixture?  Assume that argon and carbon dioxide behave as ideal gases.

So, initially I found the moles of argon in in a $\pu{1.1 L}$ vessel which is $\pu{0.06896 moles}$

Then, i subtracted $\pu{1.72 L}$ from $\pu{1.1 L}$ in order to get a volume of carbon dioxide and used it in $PV = nRT$ and i got $\pu{0.04474 moles}$ of carbon dioxide .

Finally, I used the formula for partial pressure

$\frac{\text{moles of carbon dioxide} \times\text{total pressure}}{\text{moles of argon} + \text{moles of carbon dioxide}}$ and got $\pu{0.6771 atm}$.

However, my answer is not correct according to the textbook. Where did i make a mistake?


texts: Does it matter what electrolyte we use for a Galvanic Cell?

texts:
A typical Galvanic Cell, say a Daniell cell, consitsts of two separate beaker, one containing Zn rod dipped inside aq $\ce{ZnSO4}$ and the other beaker containing Cu rod dipped inside $\ce{CuSO4}$. Does it matter what electrolyte we dip the metal in?

If we change the electrolyte of the beaker containing Zn rod to say $\ce{AgNO3}$. I would expect a displacement reaction to take place where a redox reaction occur between the Zinc rod and the Ag+ ions. No electrons will flow through the external wire. What if I replace the electrolyte with a solution of a metal that is less reactive then the metal dipped in? eg. $\ce{NaCl}$, $\ce{MgCl2}$, $\ce{KCl}$(aq). Would my cell still work?

Also, I don't understand the need of a porous pot OR salt bridge in a galvanic cell. Why would it matter if the solutions are mixed together? Why not just have one single beaker, containing an electrolyte $\ce{KCl}$(aq), and have the two different metals dipped into it. In fact, if the solutions are mixed together, there will not even be unbalance charge accumulation, and the porous pot/salt bridge would not be necessary?


texts: Luminescent materials under IR radiation?

texts: is there a database somewhere of materials that are luminescent  when exposed to Infra Red radiation?


texts: Propane Combustion in a Gas Grill with Irregular Flameouts

texts:
I'm troubleshooting a problem with a brand-new propane gas grill that is experiencing flameouts and making puffing/popping sounds.  I'm asking here because I want to understand the basic chemistry that would cause this problem.

The problem is demonstrated in this video.

I've already been through all the expected troubleshooting steps:

Replaced the gas regulator
Replaced the burner
Tried three different propane tanks

The grill was purchased about 3 weeks ago. The valve/regulator assembly was replaced last week, and the burner was replaced yesterday, so both parts are essentially new and unused.

It's hard to tell from the video if the puff causes the flameout or the flameout occurs first, followed by accumulation and detonation of a small amount of unburned propane.

I would like to understand the chemistry principles that govern the combustion of propane in a grill, and what design flaw(s) could cause this behavior.


texts: Why do metallic elements have a very small band gap while nonmetallic elements have a large band gap?

texts: I recently was going over solid state bonding and conductivity. I was wondering why metallic elements (such as sodium, iron, etc.) have a small band gap / no band gap (as conductors that have the fermi level in the overlap between the valence and conduction band) while elements such as carbon have such large band gaps. What distinguishes carbon and sodium, for example, such that carbon is an insulator while sodium/iron is a conductor of electricity? If you could explain in terms high school to undergraduate level chemistry, that would be great.


texts: Where to put the number in organic nomenclature?

texts:
Should one write 4-hydroxypentan-2-one or 4-hydroxy-2-pentanone?
It has been seen that both have been used frequently.


texts: Can nitric acid be used to create an acidic medium for redox reactions?

texts:
While reading about redox reactions, every time I found that $\ce{H2SO4}$ is used for creating an acidic medium.
My question is - can I use nitric acid to create an acidic medium?


texts: Are such high oxidation states as reported by Vojovodic et al. possible?

texts:
I am a student in theoretical chemistry and I am confused about the paper: Trends in adsorption of electrocatalytic water splitting intermediates on cubic $\ce{ABO3}$ oxides (Montoya, J. H.; Doyle, A. D.; Nørskov, J. K.; Vojvodic, A.; Phys. Chem. Chem. Phys. 2018, 20 (5), 3813–3818. DOI: 10.1039/C7CP06539F), where the authors report DFT calculations on the oxides:

$\ce{MgBaO3}$ ($\ce{Mg^3+}$ and $\ce{Ba^3+}$)
$\ce{NaLaO3}$ ($\ce{La^5+}$)
$\ce{CaBO3}$ and $\ce{SrBO3}$ ($\ce{B^4+}$)
$\ce{ZrNaO3}$ ($\ce{Zr^5+}$)
$\ce{ScSrO3}$ ($\ce{Sc^4+}$)
$\ce{CaCuO3}$ ($\ce{Cu^4+}$)

... and many more. Are these oxidation states even possible?


texts: Internal standard with low T1 for NMR quantification of ammonia

texts:
I am trying to quantify low levels of ammonia with NMR. The good news is that ammonia has a very low T1 (<0.5) which shortens d1 a lot. However, I cannot find any internal standard with a T1 that is as low as ammonia so that I can use absolute qNMR for quantification. For example maleic acid would require around 10 times longer relaxation, because the T1 is around 3-5s which reduces the LOD of cause.

Regards,
Martin


texts: Manganese oxide reacts with tin(IV) hydroxide?

texts: I have a problem on my chemistry summer homework in which it asks me to predict the product of “solid Manganese-Oxide when it reacts with tin(IV)-hydroxide in aqueous solution”. My issue is that there are multiple manganese oxides (https://en.wikipedia.org/wiki/Manganese_oxide) And that, normally,  neither hydroxide nor tin are water soluble.  How do I solve this?  I am allowed to answer that there will be no reaction, but how do I prove this, and how am I sure?  This is for A.P. Chemistry summer homework.


texts: absorption spectrum of water at different wavelengths

texts:
I know I can get the visible absorption spectrum of water https://en.wikipedia.org/wiki/Water_absorption But how does one go about getting and testing what the absorption spectrum is for a glass of water in the audio range of (0hz to 20000hz) I know nasa uses water to absorb sound https://youtu.be/08aHEmuzMLI.
How can I measure what the sound absorption spectrum is in a glass of water?


texts:
Find threshold frequency, in $\mathrm{Hz}$, of a metal if it emits an electron with kinetic energy of $2.74 \times 10^{-19}~\mathrm{J}$ when illuminated with light with frequency of $1.49 \times 10^{15}~\mathrm{Hz}$.

I am not sure what to do with this.


texts:
I read in the paper that:

  The reduction of diphenyl diselenide using lithium aluminum hydride generates a selenolate ion having Lewis acid character due to the oxygenophilic nature of the aluminium.

Can any one explain me the meaning of the bold expression, please


texts:
Here it writes that nitrohydrochloric acid (possibly Aqua Regia) is of the ratio of $18:82$, which is $1:4.56$ in a simpler form. On Wikipedia and every other source i found the ratio $1:3$. So what's the truth behind this?
Also is Aqua Regis a valid way to call the mixture? On Wiktionary it says that this is a synomym of Aqua Regia but why would it have such a different ratio then?


texts: Stability of alkenes by hyper conjugation

texts:
I have learnt that for carbocations, electrons are delocalized from the $\ce{C-H}$ $\sigma$-bond to the empty p-orbital of carbon.

Moreover, alkenes are stabilized by the delocalization of electron from $\ce{C-H}$ $\sigma$-bond to the empty anti bonding $\pi$ molecular orbital.

But, don't electrons in anti bonding molecular orbitals lead to instability? So, how does hyper conjugation lead to stability of alkenes?

I believe this question has already been asked before, but I couldn't find any satisfactory and/or relevant answers.


texts: Reaction between Salicylaldehyde and 2-Benzoylpyridine

texts:
In a paper by Sheng et al (10.1016/j.dyepig.2018.07.036) the authors synthesize the compound MZC as shown in the scheme below.

I'm looking for information about what the reaction mechanism is that underpins this reaction. If anyone can share some insights it is much appreciated.

In the experimental section  it is written

  2-Benzoylpyridine (4 mmol, 0.732 g) and ammonium acetate (22 mmol, 1.70 g)
  was dissolved in acetic acid (30 mL) and followed by the addition of salicylaldehyde
  (6 mmol, 0.733 g). The reaction was refluxed for 6 h. The resulting solution mixture
  was cooled to room temperature and cold water was then added to the mixture. The
  solid was collected by filtration and washed with a small amount of cooled water,
  which was purified via recrystallization using acetonitrile to give MZC (0.687 g, 60 %
  yield).


texts: Determine rate law from experimental data

texts:
For the reaction A -> B + C we have the following experimental data.

\begin{array}{cccc}
\text{Experiment} & \ce{P_A} &\ce{P_B} &\ce{P_C} & \text{Reaction rate}\ce{}\\\hline
1 & 1 & 1 & 1 & 3.5\\
2 & 5 & 1 & 1 & 1.1\\
3 & 10 & 1 & 1& 0.7\\
4 & 2 & 5 & 1& 1.9\\
5 & 2 & 10 & 1& 1.6\\
6 & 3 & 0 & 5& 1.5\\
7 & 3 & 0 & 10& 1.2\\
8 & 0 & 5 & 8& 0\\
9 & 3 & 3 & 3& 1.4\\
\hline
\end{array}

I have been searching around the internet, but it seems like many of the examples that I found include fewer experiments and/or different chemical reactions.
I am thus wondering what method one can use to find the appropiate rate law, and if one uses all of the experimental data? Looking at all the data at once it is harder to see the pattern.

Supposedly this should be possible to do without using regression with Excel or other computer software.

Any suggestions are highly appreciated!


texts: How can I find the symmetry labels of atomic orbitals in a molecule?

texts:
What are the symmetry labels for the p and d orbitals of platinum in $\ce{[PtCl4]^2-}$?

I understand how to find the point group of a molecule, but am not sure how to use the character table to find the irreducible representations corresponding to the orbitals.


texts: Spatial Wavefunction Symmetries and Identical Particles

texts:
I was reading this and it mentions in the 3-electron section, that for a spacial wave function to be symmetric under fermion swapping, it must be a function of even parity. Similarly for anti-symmetry under fermion swapping, it must be a function of odd parity.

It is not immediately obvious to me why parity symmetry $(-1)^l$ has anything to do with the bosonic or fermionic properties of the spatial wave function. So I suppose my questions are:

Is it true that spatial inversion is the same symmetry as swapping?

And if so, why?


texts:
What is a water blank?

I am doing some research and I am suppose to prepare a solution. I should mix 10g of soil with 95ml of water blank in order to create a soil suspension.

My problem is I am not English and I have no idea what a water blank is. I have a feeling the type of water is pretty important here though. (can't find what it is on the internet).

Help please. A simple definition/description will do.


texts: Are there chiral carbons in PVC polymers?

texts:
PVC polymers are formed from the monomer CH2=CHCl.
Below picture is a section of PVC molecule.
Is there any chiral carbon centre in this polymer molecule. If yes, then how?

I have a source of CAIE examination paper implying carbon bonded to Cl group is chiral, but as in the picture the group on both sides of that carbon is same.
(Source, Qno:38)


texts: Are all degenerate d-orbitals identical?

texts:
This discussion spun off from the comments to another question. The basic idea of that question was that electrons don't have a preferred order of filling in $p$ orbitals, i.e. the first electron will fill in the $p_x$ orbital just as well as it will fill in the $p_y$ or $p_z$ oribtal. This is because in the absence of electromagnetic fields, all p-orbitals are degenerate, and the coordinate axes are things we arbitrarily assign, so, the degenerate $p$ orbitals are all identical.

I wonder if the same can be said about $d$-orbitals. Four of them ($d_{xy}$, $d_{xz}$, $d_{yz}$, $d_{x^2-y^2}$) feel identical to me, as they all have four perpendicular and coplanar lobes (but I could be wrong). The fifth one - $d_{z^2}$ - doesn't look identical to me. Its positioning of the lobes is wildly different from the other four.

This makes me wonder,

  Are all degenerate $d$-orbitals identical?

By identical, I mean that the electron filling order has no preference. (but this might not be the best definition of identical orbitals please mention if you have a better one)

Remarks:

I didn't mention $f$-orbitals because they have even ridiculous orbital structures (4 types have six lobes, 2 have 8 lobes, and 1 seems to be a advanced version of $d_{z^2}$ with two rings. Crazy!), but in case their answer is remotely similar, please consider mentioning them in your answer for completeness.
I have talked about atomic orbitals and not molecular orbitals (just in case that made the answer different).


texts:
I was looking at a poster for an international chemistry olympiad. Its background contains some random elements as periodic table tiles.

One of them said "Estrontium." A google search returned nothing but clip art.
Is this an accepted spelling internationally (similar to the way Spanish speakers prefix "e" on words starting with "s" followed by a consonant) or a careless typo on their part? My chemistry teacher was equally confused.


texts:
The formula for the work done by adiabatic expansion of gas is
$$W = C_V\,\mathrm dT.$$
Why the volumetric heat capacity $C_V$ is constant and not the heat capacity at constant pressure $C_p?$ If the system is at constant volume, it is a isovolumetric process and hence no work can be done in that case.


texts:
The first line of the Wikipedia article on Organic Chemistry says:

"Organic chemistry is a subdiscipline of chemistry that studies the structure, properties and reactions of organic compounds, which contain carbon in covalent bonding."

This suggests that carbon compounds with no covalent bonds are excluded but what are these compounds?  I am aware that other types of bonds may occur and be important but, even when they do, the compound still seems to be regarded as organic.

What is an example of a carbon compound excluded by the clause "which contain carbon in covalent bonding"?


texts: Pool Water Electrolysis for Rust Removal

texts:
I had an old tool I was trying to remove rust from using electrolysis.  I used a solar panel and chlorinated pool water.  I have had a difficult time online finding what the products of the reaction should be.  After hours in the sun the water turned to an orange reddish color and then almost green.  I had read about doing this with salt water and it producing chlorinated gas, does pool water go through the same reaction?

Thanks & Regards


texts:
At the supermarket they sold tea for hard water. (Hard water is water with limestone/calcium carbonate in it).

There appears to be a chemical modification for foods using this type of water.

My question is: What is chemically different about tea for hard water?

Edit: here is the list of ingredients: tea (only)

Edit 2:
- it appears hard water is more basic so a tea mix that is more acidic is required (perhaps)


texts:
(JUST A HEADS UP I’m 15 years old and new to chemistry) So I was recently looking around the house looking for products that I can extract chemicals from and I found a bottle of cleaning Vinegar ( 5% acetic acid), so I decided to make some acetate compounds, but when I first started I thought it would be a simple 1 step synthesis. I was wrong. I soon realized you must have hydrogen peroxide and acetic acid to make zink and copper Acetate.

So I tried making nickel acetate, with no luck. So then I tried to make nickel chloride knowing this new hydrogen peroxide step. I took a pure nickel sheet and put it in a beaker then added calcium hypochlorite and hydrogen peroxide. And it worked! The solution turned light green over a few hours, and it had a gas being produced. And also a black Precipitate which was most likely nickel oxide (I filtered the precipitate off before taking the picture)

But just to check myself I tried to find this process online, to no avail. So now I’m wondering if I did something wrong and got the wrong product or no one does it through this process. If you can check my process to make sure it’s possible and I didn’t waste my time I would Appreciate it. Thanks in advance.


texts:
Which substance can be easily adsorbed by charcoal?

$\ce{CO2}$
$\ce{SO2}$
$\ce{H2}$
$\ce{He}$

I thought the answer was (3) because the intermolecular forces are weak. So charcoal can easily adsorb hydrogen. But answer given is (2) which has strong intermolecular forces. Is my reasoning wrong?


texts: When does a piston stop in an irreversible process?

texts:
Suppose we have an ideal gas filled inside a container fitted with a piston. The external pressure is equal to internal pressure.
If we suddenly decrease the external pressure, we say that the gas will expand until the internal pressure and external pressure become equal.
Considering an irreversible process, shouldn't the gas expand beyond that point because by that time the piston will have gained some velocity?


texts: What is the density of compressed natural gas (CNG) used in vehicles?

texts: I would like to know the density of the compressed natural gas used for natural gas vehicles in order to complete the formula in this Mathematics Stack Exchange post.


texts: What will be the arrangement of crystals if a solution of two salts, say, Sodium Chloride and Potassium Chromate, is dried? Will one salt crystallize before the other and become the crystallization nuclei of the other? Would both types of crystal form in a chaotic mixture? Or would they interact to form some new lattice?


texts: Scale to be considered for comparing electronegativities of nitrogen and chlorine

texts:
The Pauling scale gives the $\chi$ values of $\ce{N}$ and $\ce{Cl}$ to be $3.04$ and $3.16,$ respectively, but the Allen scale gives the $\chi$ values of $\ce{N}$ and $\ce{Cl}$ to be $3.066$ and $2.869,$ respectively.

Another point that should be made note of is that the most electronegative element as per Allen scale is $\ce{Ne}$. So, why is it accepted in the first place? And whose electronegativity is actually greater?


texts: Why the H+ ion remains with the molecule even though there is no bond between it and hyperconjugative structure?

texts:
In hyperconjugation, it is known that form an $\alpha$ hydrogen, one $\sigma$ electron goes to the corresponding carbon carbon bond, and there is apparently or practically, no bond between the hydrogen and carbon. I read in a textbook,

  although one $\ce{C-H}$ bond of the alkyl is shown to be broken in each hyperconjugative structure, $\ce{H+}$ is never free from the rest of the molecule.

But then, still there is no bond. Is there any specific reason why the $\ce{H+}$ ion remains with the molecule though there is no bond attaching the ion to the rest of molecule?


texts: CO2 + High humidity = transperent substance?

texts:
First I want to point out that I am not a chemist, sorry for bad description.
I have CO2 incubator. CO2 concentration is 10-20% and the humidity level is around 90%. I was using a humidity sensor to measure humidity and some kind of transparent substance have formed around the sensor. Sensor becomes unprecise and had a slow response time. Substance almost looks like plexiglass.
Is it possible that carbonic acid which is forming from CO2+H20 -> H2CO3 is somehow reacting with integrated circuit case or sensor and forming some kind of glass-like substance?
New sensor:

Used sensor:


texts: Why does light and heat yield different stereochemistry in electrocyclic reactions?

texts: In my organic chemistry II class, we started learning about electrocyclic reactions. We learned heat and light yield different products. So my question is, how do they work differently to yield those different products?


texts: Which solution has the highest total molarity of ions and why?

texts:
(a) 0.008 M $\ce{Ba(OH)2}$
(b) 0.010 M $\ce{KI}$

The answer is "a" but I do not understand why. The book says that "a" is a strong electrolyte with a total ion concentration of 0.024. How did they calculate the concentration from the information that they gave? And why is it a strong electrolyte based on that calculation. I thought strong electrolytes were (solutes) ions that dissolved completely in a solvent/solution?


texts:
Recently we learnt that there is a depression in the freezing point when a non-volatile solute is added to the solvent. Our teacher explained this phenomenon with a graph where the vapour pressure of the solution and pure solvent intersects with the vapour pressure of the solid solvent. my question is: wouldn't the vapour pressure of the solid solution be lower than the vapour pressure of the solid solvent(that would make another curve in the graph)? Because, the non-volatile solute is still blocking the surface of the solvent, thus reducing the vapour pressure.
The solution is of a solid non-volatile solute in a liquid solvent


texts: Distinguish between two possible configurations for angular momentum in carbon atom

texts:
Consider the possible values of $S$ and $L$ for carbon configuration $1s^2 2s^2 2p^2$ and the corresponding rapresentations with arrows indicating the spins (consider only $S=0,L=0$ and $S=0,L=2$, as for $S=1,L=1$ some are missing).

I can't understand which one of the two representations indicated in red belong to $S=0,L=0$ state and which one to the $S=0,L=2$ state (I took a guess making the picture).

The spin wavefunction is in all cases antysymmetric ($S=0$) and equal to
$$\chi =\left(\, |\!\uparrow_1 \downarrow_2\rangle-|\!\downarrow_1 \uparrow_2\rangle\,\right)\div\sqrt 2$$

Therefore the spatial wavefunction $(L)$ must be symmetric for Pauli principle and in the second red configuration is

$$\Psi =p_0 (1) p_0 (2)$$
in the first one  is

$$\Psi= \left[p_- (1) p_+ (2)+p_+ (1) p_- (2)\right]\div\sqrt2$$

The wavefunctions are different so there must be a difference between the two red configurations, but which of them should belong to $S=0,L=2$ and the other to $S=0,L=0$ and why?


texts:
I was making coffee with a cup of boiling milk which was 2 days old. I used instant coffee powder and some sugar for the making of it. Tried to make a very hot coffee but usually prefer medium hotness. When I mixed the hot milk with coffee powder, I immediately observed coagulation.
Then, I decided to use an unopened milk packet and boiled it the same way. But this time I used a relatively more roasted coffee powder with same amount of common sugar. Again I observed coagulation but the particles were smaller.

I know that milk is a colloid and can be coagulated by using an acidic compound.
The casein starts coagulating at pH 4.6,
But I don't think that coffee is acidic enough to lower the pH. As in my second experiment, I've used a lesser acidic coffee powder (more roasted) but still observe coagulation.

In fresh dairy milk, is there any relation between titratable acidity and heat coagulation?
Does hydrogen ion concentration determine the coagulation?
Is it the coffee power or the milk or the temperature?
How to avoid this effect?


texts:
Why is the oxidation potential given a positive sign and the reduction potential a negative one?

Also, in my book a bunch of formulas are given without any explanation:

$E^{o}_{cell}= $ Oxidation potential of anode + Reduction potential of cathode

$E^o_{cell}=$ Standard reduction potential of cathode - Standard reduction potential of anode

$E^o_{cell} =$ Oxidation potential of anode - Oxidation potential of cathode

I am unable to get any intuition for this and the physics behind these signs. Could someone please provide an intuitive explanation of what's going on?


texts: What is the IUPAC nomenclature of alkane with large numbers of C atoms (more than 200)?

texts: What is the IUPAC nomenclature for alkanes with large numbers of $\ce{C}$ atoms (more than 200)? For example, what is the IUPAC accepted name for $\ce{C_{205}H_{412}}$?


texts: Gaussian09 vs home made Hartree-Fock implementation

texts:
I implemented a restricted Hartree-Fock (RHF) calculation in the STO-3G basis set, as described in Szabo and Ostlund's book [1]. I managed to reproduce the energies of all their calculations ($\ce{H_2}$, $\ce{HeH^+}$, $\ce{H_2O}$, $\ce{CO}$, $\ce{CH_4}$ and $\ce{FH}$) with precision. For example, for $\ce{N2}$ I found
$$
E_\text{tot}^\text{HM} = -107.49583784393724 \text{ a.u.}
$$
while in the book they report the following (p. 192)
$$
E_\text{tot}^\text{Szabo} = -107.496 \text{ a.u.}
$$
The situation is analogous for all other molecules I tested.

Now I am trying to implement the calculation of forces, in order to perform Born-Oppenheimer molecular dynamics. I will start to compute the gradient of the PES by finite differences (computationally costly but easy to implement). In order to check my implementation I wanted to use Gaussian09 (for the first time!) as a benchmark because we don't find many force calculations on standar books. In order to check that my input file is correct (i.e. the options can reproduce my "dumb" implementation) I performed a single point calculation for the $\ce{N2}$ dimer. Surprisingly I found
$$
E_\text{tot}^\text{G09} = -106.765838750 \text{ a.u.}
$$
which is quite different from my result. The input file I used is the following:

%NProcShared=2
%Mem=1GB
#P RHF/STO-3G SP Symmetry=None Units=Bohr Pop=None Guess=Core

RHF

0 1
N 2.074 0.000 0.000
N 0.000 0.000 0.000

I tested the same structure on the input file for $\ce{H2O}$:

%NProcShared=2
%Mem=1GB
#P RHF/STO-3G SP Symmetry=None Units=Bohr Pop=None Guess=Core

RHF

0 1
H +1.4305507125e+00 +0.0000000000e+00 +0.0000000000e+00
H -1.4305507125e+00 +0.0000000000e+00 +0.0000000000e+00
O +0.0000000000e+00 +1.1072513982e+00 +0.0000000000e+00

In this case I find
$$
E_\text{tot}^\text{G09} = -74.9629400524 \text{ a.u.}
$$
wigh Gaussian09, while with my program I have
$$
E_\text{tot}^\text{HM} = -74.962937313769473 \text{ a.u.} = E_\text{tot}^\text{Szabo}
$$
For $\ce{H2O}$ everything seems to work fine. In a similar way, I get matching results also for $\ce{CH_4}$, $\ce{FH}$ and $\ce{CO}$.

There is a problem with the $\ce{N2}$ molecule (or simply with the input file) I am not considering?

Which is the best set of options for Gaussian09 that can emulate a home-made Hartree-Fock program (written following closely Szabo's book [1])?

[1] A. Szabo and N. Ostlund, Modern Quantum Chemistry, Dover, 1996.


texts:
Given that $\ce{Al2O3}$ is face-centered cubic (cubic-closest packed) with respect to oxide anions, I am instructed to find the oxidation state of each aluminum ion "fragment" in the unit cell.

Let's suppose that the picture above is of $\ce{Al2O3}$ and not $\ce{NaCl}$. The larger oxide ions are green; the smaller aluminum cations are purple.

There are a total of 4 oxide ions in a unit cell, and a total of 3 aluminum ions in the unit cell.

Given that 4 oxide ions impart a charge of -8, and that a unit cell must be neutral, then each of the "three" aluminum ions must have an oxidation state of +8/3 in the unit cell, correct?

I cannot find any textbook discussing the oxidation states of atoms in unit cells ... so I am at a loss at whether my work is correct or not.


texts: The conversion of energy during electroplating

texts: I've made a test and i've faced a problem with a part of a question which says: "What is the conversion of energy occuring in electroplating? " I answered that it is conversion from electric energy to chemical energy, since in electroplating, the anode is reduced to X^n+ and n+, where n+ ions are transferred through DC power supply into the cathode and then combines with X^n+ to give again X and plates the cathode, so the electric energy(transfer of electrons through the DC power supply) is converted into chemical one(change  X^n+ to solid). I want to know if my answer is correct or not and why? Helping is appreciated


texts: Mechanism for the conversion of dimethyl cyclohexa-1,4-diene-1,2-dicarboxylate to dimethyl benzene-1,3-dicarboxylate using bromine

texts:
Question

Convert the first compound into the second using only $\ce{Br2}$

I tried solving it by making a 3-ring with $\ce{Br+}$, and then making one of the oxygens break that ring. Than I used $\ce{Br-}$ to steal an $\ce{H}$ and get a lone pair on one of carbons. Lastly, I used the lone pair to create a double bond. Am I on the right track?


texts: How to determine which ions will pair to form a compound in an aqueous solution?

texts:
Let us assume we have an aqueous solution with the ions $\ce{A+}$, $\ce{B+}$, $\ce{C-}$ and $\ce{D-}$. Which ions will form a bond and why? Will the compound formed be $\ce{AC}$ and $\ce{BD}$ or $\ce{AD}$ and $\ce{BC}$?

Is there any general rule to identify the compounds we have at the end?


texts: which conformer stable of piperazine, when hydrogen of N in axial or in equatorial, or lone pair? why?


texts:
I recently learnt that the reason for low solubility of mucic acid as compared to glucaric acid was more hydrogen bonding in the crystal state of mucic acid as compared to glucaric acid.

I would like to know why mucic acid has more hydrogen bonding? Does symmetry of the molecule play a role? If so how?


texts: Mechanism of the reaction of cyclohexanone and nitric acid to form Adipic acid

texts:
Can I get some help in figuring out the mechanism for this reaction.
Adipic acid is a molecule with two carboxylic groups,but I can't see how that happens. My initial thoughts involved that the carbonyl group in cyclohexanone is protonated,but I couldn't get any further as I couldn't figure out what would happen after that.


texts: Why do we use different arguments for determining the strength of hydracids and solubility of ionic compounds?

texts: HI is a stronger acid than HF. Why? Because when dissolved in water, the bigger iodide ion handles the negative charge way better than the small fluoride ion. So Iodide ion is a weak conjugate base making HI a strong acid.  Which one is more soluble in water, AgF or AgI? Answer is AgF. Why? It is an ionic compound and by Fajans' rules, an ionic bond shows more covalent character if it is more polarised. The smaller the anion, the less polarisation there will be, thus more ionic character, hence more solubility. But what if I said that AgI is more soluble in water, because what happens when AgI dissolves in water? It turns into Ag+ ion and I- ion. And I- handles the negative charge better than F-. What's wrong with that?


texts: Three stacked arrows, what does it signify?

texts:
I was checking the mechanism for the Lossen Rearrangement, when I came across the chemical reaction denoted as follows:

I couldn't find any resource where this notation was talked about.
What do the three arrows stacked as follows mean? A possible example where this is applied in literature would be appreciated.


texts: How does baking soda works as an desiccant?

texts:
The thing is that I did a project from a website which is about the science of mummification and I can't find a way to explain the process of desiccation of the hot dog with the baking soda.

By this I mean to answer questions like: Does the baking soda absorb or adsorb water? If it adsorbs then which type of adsorption is it? What's happening in details between the hot dog and the surrounding baking soda?

Here is the link to the project

My results did show a decrease in mass and size which is explained in the lost of water from the hot dog but how?


texts: What is the origin of the transferred oxygendianion in redox reactions?

texts:
How come the oxygens transferred in redox reactions are always the $\ce{O^{2-}}$anion?

For example, I have this set of rules, and the rules are implicitly referring to the $\ce{O^{2-}}$  anion, a potent base (otherwise the rules wouldn't make sense; for example, it makes sense that a base in acidic solution is protonated to water, and that a strong base in basic solution is leveled to hydroxide ion).

In other words, how come, when electrons are transferred, such as in this unbalanced reaction:

$\ce{ClO_{3}^- + 6I^- \leftrightharpoons 3I_2 + Cl^-}$

The $\ce{O^{2-}}$ anion is formed (if only to be consumed again)? I remember my prof would say that specifically 3 $\ce{O^{2-}}$ anions "disappear".

Why not the $\ce{O^{-}}$ anion or simply $\ce{O}$? Does this have to do with stability?


texts: In a test I was asked why the hydrolysis equilibrium of Urotropine (Hexamethylenetetramine) in neutral solution lies far on the side of the reactants. Well I had no idea and I'd be very glad if somebody could give me an answer on that question.


texts: What lab equipment did Marie Curie use to isolate radium?

texts: My experience in growing crystals for condensed matter physics has been sealing grams of material in ampoules which get heated in laboratory furnaces, so I don't have the experience to understand how Marie Curie managed to go through tons of pitchblende to isolate radium, especially given her limited resources. How were the samples heated, and how would she have kept her samples from getting oxidized? It seems like making lots and lots of ampoules would be impractical.


texts:
I'm not totally sure which Stack Exchange community this would go in, but Chemistry seemed best.
I've been thinking for a long time now, that it would be cool to have a program where you could design your own atomic models, from the sub-atomic scale and up, then test them in a real situation. You could create anything from simple molecular structures to...anything.
I've looked around online, but there aren't any programs that you can build your own atomic structure. Anyone know if there are any out there like this?

EDIT: I've tried a few other programs, including Avogadro, this, and another one by PHET.


texts: Reaction of potassium cyanide with 2-(chloromethyl)furan

texts:
What would the mechanism for the reaction between 2-(chloromethyl)furan and potassium cyanide be, as detailed below?

I know that for 6-membered rings like pyridine, a $\mathrm{S_NAr}$ reaction can occur. However, I'm not sure as to how the mechanism differs between the two in a way that the cyanide group is added at the 5-position instead of the methyl group.


texts: Are these chemical reactions with amino acids possible, and if so, what are they called?

texts:
In high school, I am taught that the synthesis of two amino acids of the form $\ce{H2NR1COOH}$ and $\ce{H2NR2COOH}$ is a condensation reaction that produces a polypeptide $$\ce{H2NR1COOH}+\ce{H2NR2COOH}\to\ce{H2NR1CONHR2COOH}+\ce{H2O}$$ where $\ce{R1}$ and $\ce{R2}$ are arbitrary components within each acid. Then I started experimenting with different positions that yield isomers of the polypeptide.
Examples

Water is formed though the pairing of the two $-\ce{OH}$ groups $$\ce{H2NR1COOH}+\ce{HOOCR2NH2}\to\ce{H2NR1COOCOR2NH2}+\ce{H2O}$$ which forms something that resembles an ester?

Water is formed through the pairing of the $-\ce{OH}$ and $\ce{H2N}-$ groups but the oxygen atom is taken instead from $\ce{C=O}$ $$\ce{H2NR1COOH}+\ce{H2NR2COOH}\to\ce{H2NR1C(OH)NR2COOH}+\ce{H2O}$$ where essentially the hydrogen atom from $-\ce{CONH}$ has shifted one place.

Are these reactions directly possible? If so, are there special names for
a) the reaction and
b) the type of product formed?

I am at an elementary level in chemistry so more detailed explanations would be appreciated.


texts: Effect of water viscosity (increased due to NaCl concentration) on dissolution rate of CO2

texts:
We did an experiment involving different $\ce{NaCl}$ concentration(ranging, 1-4%) on 100 mL of water. Our aim of the experiment was to find the dissolution rate of $\ce{CO2}$in the brine solvent. We did some research and found that $\ce{NaCl}$ increases the viscosity of the solvent, which in-turn decreases the dissolution rate. We want to explain how the entire process works, in a microscopic level.

Answers with good source would be good.


texts: Why is the lanthanide element Thulium malleable?

texts:
I was doing some research about Thulium and every website says that it is malleable, but doesn't explain why.

What chemical properties does Thulium possess which makes it malleable?


texts:
What is the pH of a solution of $3.4 \times 10^{-10}$ moles of $\ce{HCl}$ in a volume of $\pu{150.7L}$?

This is dilute so I expect pH to be high.

$$\frac{3.4 \times 10^{-10}\ \mathrm{mol}}{150.7\ \mathrm L} = 2.26 \times 10^{-12} \frac{\mathrm{mol}}{\mathrm L}$$

Then pH is 11.65. Is this correct?


texts: Concentration of product at a time t in a reaction

texts:
A reaction was given $\ce{A<=>B}$ The rate constants for forward and  backward reactions were given as $k_\mathrm{f}$ and $k_\mathrm{b}$. The initial $\ce{[A]}$ was given as $a_{0}$ and the $\ce{[B]}$ at a time t (before equilibrium is attained) was to be calculated.

I tried solving it as follows -

For A I wrote -

$$\frac{\mathrm{d}[\ce{A}]}{\mathrm{d}t} = k_\mathrm{b}\ce{[B]}-k_\mathrm{f}\ce{[A]}$$

and similarly for B -

$$\frac{\mathrm{d}[\ce{B}]}{\mathrm{d}t} = k_\mathrm{f}\ce{[A]}-k_\mathrm{b}\ce{[B]}$$

Combining these two I got a 2nd order differential equation and wasn't able to proceed further. Is there something wrong with my approach or my equations?


texts: What is the fabric in heating mantles made of?

texts:
An ordinary lab heating mantle often has a white fabric coating for the flask compartment, which looks like an inorganic fiber:

Image source

I'm pretty sure that for some time in the past asbestos was used for that; these days I think it's some kind of woven fiberglass (assuming the heating element produces elevated temperatures up to about $\pu{400^\circ C}$), but I'm having hard times finding an exact chemical composition.

Also, what kind of chemicals can react with this coating? I guess something like molten $\ce{NaOH}$ and the melts of alkali metals can cause some damage, but I'm not sure.


texts: Formation of a pH gradient using carrier ampholites

texts: In a technique called isoelectric focusing, the crucial part is the formation of a pH gradient using carrier ampholytes. What is the exact principle by which the gradient is formed? How do the ampholytes "know" exactly where to migrate, since they are the only protonizable chemical species in the solution?


texts: Spin of electrons about it's own axis, release of energy & COLLAPSE of atom?

texts: An electron spins about it's own axis. So it has rotational accln. Thus, according  to Maxwell's Electromagnetic Theory , Rotational Kinetic energy must be released. Thus, at some pt. of time , shouldn't the energy of an electron become 0 & then shouldn't the electron move out of  the atom, eventually leading to the atom only having the nucleus .


texts: I know that in diamond carbon atoms occur in 3d geometry but i want to ask that why it is in shape of diamond not like some other 3d geometrical shape like cube or cuboid?


texts:
Are graphite and hexagonal boron nitride aromatic?

Graphite has a planar network of 6-membered rings with each carbon connected to three other carbons. Since the valency of carbon is not satisfied, there will be some $\pi$-bonds. Can graphite act like an aromatic system? Can I explain this using Hückel's rules?

Hexagonal boron nitride has a similar structure. So if graphite exhibits aromatic character, then so will boron nitride (like inorganic benzene and benzene).


texts: Propose a reaction mechanism that explains the rate law for the formation of dinitrogen pentoxide

texts:
The reaction is:

$$\ce{NO(g) + NO2(g) + O2(g) -> N2O5(g)}$$

From the experimental data, I have found the rate law to be: $$\ce{Rate~=~k[NO][NO2]}$$

This means the overall reaction does not depend on $\ce{O2(g)}$.

Can someone suggest how I go about building the elementary steps to form the reaction mechanism?


texts:
According to my Organic Chemistry Textbook:

Benzene can be reduced to 1,4-cyclohexadiene by treating it with an alkali metal (sodium, lithium, or potassium) in a mixture of liquid ammonia and an alcohol. This reaction is called the Birch reduction.

Why the conjugated 1,3-cyclohexadiene is not formed in this reaction (as conjugated molecules are more stable)?


texts: Why does ozone disproportionate on reaction with potassium iodide?

texts:
In this redox reaction, iodide ion is oxidized to iodine and ozone reduces to hydroxide ion.

$$\ce{2KI + O3 + H2O -> I2 + O2 + 2KOH}$$

This seems like a redox reaction since iodide ion is getting oxidized and ozone is getting reduced. Then why is $O_{2}$ formed in this reaction?


texts: What are the currently most accurate sources for lists of the values for elemental properties

texts:
I have a hopefully simple question. I am a tutor working with a student that wants to know where to find the most recent accurate measurements for elemental properties. He's only in Chemistry I, so he's not looking for every property out there calculated multiple ways. I think he (and I) just like looking at the best sources. So we're looking for the following:

Latent heat of fusion
Latent heat of vaporization
Melting point
Boiling point
Density
Specific heat
Ionization energy
Atomic radius (metallic and covalent)
Atomic mass
Electronegativity
Commonality and uncommonality of charges (like oxygen is commonly -2 but is also -1 in peroxide)

I can point him to wikipedia or https://ptable.com/#Properties/Series for some of the information, but I myself don't know where the most legitimate sources for these values can be found. My CRC handbook (97th edition) lists ionization energies, but for atomic weight it doesn't list the weight of the most common isotope of elements like Ac. Also, it's a few years old.
My question is, what are the current best sources of accurate values for each of these properties?


texts: How to compute the NMR shift in Gaussian09 for only one specific atom in a bigger unit cell?

texts:
I am trying to compute the NMR shift for a specific atom in the middle of the surrounding crystal unit cell (1 surrounding anion sphere and 1 cation sphere) in Gaussian09. I only need the chemical shift for the middle atom.

How can I only compute the shift for this atom, and leave out the rest? And would it even save any computation time if I did?


texts: Hi any suggestions for a solvent for aroma oils, that has low evaporation and high diffusivity (low molecular weight and hence spreads well in the air). The solvent should also be soluble in water and should have a low evaporation rate


texts: Can I use silica gel to perform column chromatography at home?

texts: While this question has been asked and answered, it may indicate that a column chromatography qualitatively is possible. At home, is it possible after collecting silica gels from small bags of them from snack packages? Secondly, if qualitative analysis is possible, how about quantitative?