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>Is ethanoic acid most acidic in DMSO, water or methanol?
I suspect that the conjugate base would be most stabilized by a polar protic solvent (meaning it's weakest in DMSO), however, water and methanol are both protic and polar. Which causes ethanoic acid to be most acidic lowest $\mathrm{p}K_\mathrm{a}$? This was ... |
![enter image description here][1]
[1]: https://i.stack.imgur.com/wwTN1.png
The left hand species is clearly the kinetic product and the right hand product is the thermodynamically favoured product. However, I have no idea why. Can you explain? |
As Klaus and I mentioned, the first reactions seem very strange from a chemical perspective, even if they are correctly balanced. This is where a chemist needs to exercise their intuition and experience.
Balancing reactions is nothing but solving a linear system of equations, so it is entirely possible to propose re... |
![enter image description here][1]
[1]: https://i.stack.imgur.com/wwTN1.png
The left hand isomer is clearly the kinetically favoured product and the right hand isomer is the thermodynamically favoured product. However, I have no idea why. Can you explain? |
Quantum numbers give information about the location of an electron or set of electrons. A full set of quantum numbers describes a unique electron for a particular atom.
Think about it as the mailing address to your house. It allows one to pinpoint your exact location out of a set of $n$ locations you could possi... |
Quantum numbers give information about the location of an electron or set of electrons. A full set of quantum numbers describes a unique electron for a particular atom.
Think about it as the mailing address to your house. It allows one to pinpoint your exact location out of a set of $n$ locations you could possi... |
Quantum numbers give information about the location of an electron or set of electrons. A full set of quantum numbers describes a unique electron for a particular atom.
Think about it as the mailing address to your house. It allows one to pinpoint your exact location out of a set of $n$ locations you could possi... |
Quantum numbers give information about the location of an electron or set of electrons. A full set of quantum numbers describes a unique electron for a particular atom.
Think about it as the mailing address to your house. It allows one to pinpoint your exact location out of a set of $n$ locations you could possi... |
Quantum numbers give information about the location of an electron or set of electrons. A full set of quantum numbers describes a unique electron for a particular atom.
Think about it as the mailing address to your house. It allows one to pinpoint your exact location out of a set of $n$ locations you could possi... |
Is de-ionized water more corrosive to metals than tap water? I have read that it "wants" the removed ions back and will aggressively take them from any available source. |
Which substituent should be placed first (in case of alphabetisation)?
1. **isopropyl-**
2. **methyl-**
I have come across two compounds: **1-methyl-3-methoxy-4-isopropylbenzene** and **1-isopropyl-4-methylcyclohexane**
So, is “iso” taken care of in case of alphabetisation? And, are there any special criter... |
For metal complexes with $A_{2}$ or $E$ ground state terms there is angular momentum contribution to the magnetic moment which is generally positive for more than half-filled subshells and negative otherwise, and related to the spin-only magnetic moment by
$$m_\mathrm{eff} = m_\mathrm{SO}\left(1-\frac{\alpha\lambda}{... |
As Klaus and I mentioned, the first reactions seem very strange from a chemical perspective, even if they are correctly balanced. This is where a chemist needs to exercise their intuition and experience.
Balancing reactions is nothing but solving a linear system of equations, so it is entirely possible to propose re... |
What makes a molecule a good initiator of collisionally induced ISC ? Dinitrogen, dioxygen and methane have been mentioned as examples
I imagine the most important factor is ability to quench vibrational excitation so that the Franck-Condon factors for non-radiative decay are optimized. |
In potentiometric titration between ascorbic acid and iodine, when we plot the graph of EMF with volume of iodine consumed, we get a sudden decrease in EMF at equivalance point, Why? It is also negative why?
Using Nerst equation at equivalance point we get
$$E_{cell}=E_{STP}~~~(volatage ~at ~STP)$$
What is... |
In potentiometric titration between ascorbic acid and iodine, when we plot the graph of EMF with volume of iodine consumed, we get a sudden decrease in EMF at equivalance point--why? It is also negative--why?
Using Nernst equation at equivalence point we get
$$E_{cell}=E_{STP}~~~(voltage ~at ~STP)$$
What i... |
How to determine which salt will precipitate from a solution containing multiple ions? |
What makes a molecule a good initiator of collisionally induced ISC? Dinitrogen, dioxygen and methane have been mentioned as examples.
I imagine the most important factor is the ability to quench vibrational excitation so that the Franck-Condon factors for non-radiative decay are optimized. |
The closest I could think of are nozzle cover lids. Wouldn't such tool be ineffective at 'filter'-ing substances nonetheless? |
I'm learning how to apply the VSEPR theory to Lewis structures and in my homework I'm being asked to provide the hybridization of the central atom in each Lewis structure I've drawn.
I've drawn out the Lewis structure for all the required compounds and figured out the arrangements of the electron regions, and figure... |
What makes a molecule a good initiator of collisionally induced ISC? $\ce{N2}$, $\ce{O2}$ and $\ce{CH4}$ have been mentioned as examples.
I imagine the most important factor is the ability to quench vibrational excitation so that the Franck-Condon factors for non-radiative decay are optimized. |
Can we get chloroquine from 7-chloro-3-aminoquinoline by adding $\ce{CH3CHCl(CH2)3N(Et)2}$ ?
![proposed chloroquine synthesis][1]
[1]: https://i.stack.imgur.com/2TluG.png |
I have a solution containing $0.2\:\mathrm{mol}$ of $\ce{Br^-}$ ions and $\ce{SO_4^2-}$ ions each.
Now if I add excess $\ce{AgNO3}$ in this solution,
what will precipitate?
$\ce{Ag2SO4}$ or $\ce{AgBr}$ or both?
And if I add just $0.2\:\mathrm{mol}$ of $\ce{AgNO3}$, what will precipitate?
... |
Which carbocation is more stable, the ethyl or 1-propyl carbocation? |
I'm learning how to apply the VSEPR theory to Lewis structures and in my homework I'm being asked to provide the hybridization of the central atom in each Lewis structure I've drawn.
I've drawn out the Lewis structure for all the required compounds and figured out the arrangements of the electron regions, and figure... |
What is the reason why oxalic acid has its second $\ce{-COOH}$ group flipped?
I'm guessing it's something to do with steric repulsions between the $\ce{-COOH}$ groups but I'm not sure. |
I did a short experiment in which I connected a $1.5\:\mathrm{V}$ battery with 2 paper clips into a bowl of water to which I added salt. After a while, I saw a yellowish-greenish cloud inside the water around one of the paper clips, and when I took it out, the part that was in the water was more black than the rest of ... |
Identity of a green substance formed during electrolysis reaction? |
$\ce{C2H5+ vs \ C3H7+}$
There are two conflicting trends here.
Inductive effect of ethyl will be higher than that of methyl so carbocation attached to ethyl (3 carbons in total) should be more stable.
On the other hand 3 hyperconjugation structures can be drawn for the carbocation attached to methyl (2 carbons i... |
Which carbocation is more stable, the ethyl- or 1-propyl-carbocation? |
So I have an unsaturated air parcel in the atmosphere that ascends adiabatically from the $1000\:\mathrm{mb}$ level to the $700\:\mathrm{mb}$ level with its initial temperature being $10°\mathrm{C}$.
I have to find the initial specific volume in $\mathrm{m^3}\:\mathrm{kg^{-1}}$.
I know that the specific volume fo... |
I know that in acyl chlorides, there is partial triple bond character in the $\ce{C=O}$ bond *not* because the chlorine is electronically donating (due to size mismatch with carbon) but because the chlorine is highly electron withdrawing and this stimulates the oxygen into partially donating one of its lone pairs to th... |
Consider calcium carbonate *saturated* in $1.0\:\mathrm{M}$ ammonium chloride solution. I have calculated the $\mathrm{pH}$ of this solution analytically (with mass and charge balance) to be $6.92$.
Now, how would the _actual_ solution $\mathrm{pH}$ compare to the theoretical, calculated $\mathrm{pH}$ - in a genera... |
Calculate the pH of a mixture of $75\:\mathrm{cm^3}$ of methanoic acid solution of concentration $0.10\:\mathrm{mol\:dm^{-3}}$ and $75\:\mathrm{cm^3}$ of sodium hydroxide solution of concentration $0.050\:\mathrm{mol\:dm^{-3}}$. The $\mathrm{p}K_\mathrm{a}$ of methanoic acid is $3.75$.
I got $0.00375\:\mathrm{mol}$ ... |
Explain, using a chemical equation to aid your answer, why a mixture of $50~\mathrm{cm^3}$ of $0.10~\mathrm{mol\:dm^{-3}}$ ammonia solution and $50~\mathrm{cm^3}$ of $0.10~\mathrm{mol\:dm^{-3}}$ hydrochloric acid cannot be used as a buffer solution.
So writing the equation down: $$\ce{NH4OH + HCl -> NH4Cl + H2O}$$
... |
Why can't this mixture be used as a buffer solution? |
Why does $\ce{C=O}$ stretching frequency increase with ring strain?
Why does conjugation decrease $\ce{C=O}$ ring strain?
I am told that cyclopropanone exhibits a higher $\ce{C=O}$ stretching frequency than does cyclohexanone. I know that higher stretching frequencies are correlated with a shorter, stiffer, and ... |
Rotation around the double bond of azobenzene is restricted because it would distort the P orbital overlap between the nitrogen atoms. However, in the n -> pi* excited state (S1), the rotation is no longer hindered and it can isomerize.
I don't understand why this is the case. You are taking an electron from the no... |
Rotation around the double bond of azobenzene is restricted because it would distort the P orbital overlap between the nitrogen atoms. However, in the n -> pi* excited state (S1), the rotation is no longer hindered and it can isomerize.
I don't understand why this is the case. You are taking an electron from the no... |
During bond formation in Carbon, one of the electrons from the **2s** orbital jumps to one the empty ***p*** orbitals creating a hybrid orbital as seen in the figure below.
<p>
![enter image description here][1]
[1]: https://i.stack.imgur.com/hyRiO.png
Now clearly one electron from the ***2s*** orbital jump... |
Change of electron spin in Carbon after Hybridization? |
Rotation around the double bond of azobenzene is restricted because it would distort the P orbital overlap between the nitrogen atoms. However, in the $n \rightarrow \pi^*$ excited state ($S_1$), the rotation is no longer hindered and it can isomerize.
I don't understand why this is the case. You are taking an elec... |
What is a non-classical carbocation?
How is it different from a classical carbocation(if that means something)? I am confused as I have come across this term many a times on CSE but there seems to be nothing of my level of understanding on the Internet! |
What is a non classical carbocation? |
I was wondering whether the following order ([from here][1]) is correct:
- In the **first inequality**, why did 9 hyperconjugations dominated resonance effect of benzene ring?
- In the **last inequality** doesn't the 2 hy... |
So I have an unsaturated air parcel in the atmosphere that ascends adiabatically from the $1000\:\mathrm{mbar}$ level to the $700\:\mathrm{mbar}$ level with its initial temperature being $10\:°\mathrm{C}$.
I have to find the initial specific volume in $\mathrm{m^3}\:\mathrm{kg^{-1}}$.
I know that the specific vol... |
Can the compound butane-2,2,3,3-tetraol, $\ce{C4H10O4}$, be oxidized by $\ce{KMnO4}$? If so, in what conditions? As I have learnt in class, normally the hydroxy group would oxidize to form a ketone, but what about this particular case? |
Can butane-2,2,3,3-tetraol be oxidized by potassium permanganate? |
I have a wave number question which I have partially solved
**The question is:-**
What transition in He+ ion shall have the same wave number as the first line in Balmar series of H atom?
(a)7->5
(b)5->3
(c)6->4
(d)4->2
**Here's how I sovled it:-**
Note: symbol Z is the atomic number
![enter ima... |
I have a wave number question which I have partially solved
**The question is:-**
What transition in He+ ion shall have the same wave number as the first line in Balmar series of H atom?
(a)7->5
(b)5->3
(c)6->4
(d)4->2
**Here's how I sovled it:-**
Note: symbol Z is the atomic number
also 1/la... |
I have a wave number question which I have partially solved
**The question is:-**
What transition in He+ ion shall have the same wavenumber as the first line in Balmer series of H atom?
(a) 7->5
(b) 5->3
(c) 6->4
(d) 4->2
**Here's how I solved it:-**
Note: symbol Z is the atomic number
also 1... |
For those who have never had the pleasure of personally doing this, see [this][1] video. It has been known since 1807 that dissolving sodium in liquid ammonia results in a beautiful color. It was originally thought the color was due to some familiar complex instead of a solvated electron. A similar phenomenon happens w... |
In [Gaussian][1] the SCF convergence criteria is set to $10^{-N}$ by
SCF=(Conver=N)
Note that this criteria applies to the root mean square change in density matrix between two SCF cycles, while the maximum change convergence criteria is set to $10^{-N+2}$. For instance, for the default case of $N=8$ the outp... |
What is the exact meaning of GAMESS (US) SCF density convergence criteria? |
Crystals have inspired a great many chemists because they are fascinating *for a good reason*. Not only are they aesthetically pleasing, but they serve as an excellent subject to tour a variety of theoretical subjects important for understanding high-level chemistry.
Crystalline materials are made up of periodic str... |
A general rule is: crap goes in, crap comes out. A large-sample low-field 1D NMR at room temperature is usually only minimally affected by using a cheap NMR tube. There are important differences though and I’ll highlight a few.
The first distinction between prices is what the tube is constructed from: quartz obvious... |
Why signals of carbon and hydrogen atoms (in NMR spectra) are split by coupling to 19F? Some spectra books only states that "19F (natural abundance 100%) has a spin quantum number I of 1/2. The signals of carbon and H atoms up to a distance of about four bonds are split by coupling to 19F.", but there is no explanation... |
Why signals of carbon and H atoms (in NMR spectra) are split by coupling to 19F? |
Formula for calculating age by using carbon-14 (source: [HowStuffWorks](http://science.howstuffworks.com/environmental/earth/geology/carbon-142.htm))
$$
t = \frac{ln (N_f/N_o)}{-0.693}t_{1/2}
$$
The page doesn't explain what the $-0.693$ represents. What is $-0.693$?
Secondly, it says that $N_o$ is the original le... |
Carbon Dating: What to compare the new value against? |
Large elements of my answer is drawn from my own notes that I use for teaching General Chemistry II.
-----------
**What is −0.693?**
Radioactive decay processes follow first-order kinetics. A first-order reaction is one where the rate depends **only** on the concentration of one of the reactants raised to the... |
Large elements of my answer is drawn from my own notes that I use for teaching General Chemistry II.
-----------
**What is −0.693?**
Radioactive decay processes follow first-order kinetics. A first-order reaction is one where the rate depends **only** on the concentration of one of the reactants raised to the... |
When a functionalized cyclohexenyl halide undergoes $\ce{S_{N}1}$, does a racemic product form (due to ring flipping) ? |
Formula for calculating age by using carbon-14 (source: [HowStuffWorks](http://science.howstuffworks.com/environmental/earth/geology/carbon-142.htm))
$$
t = \frac{\ln (N_f/N_o)}{-0.693}t_{1/2}
$$
The page doesn't explain what the $-0.693$ represents. What is $-0.693$?
Secondly, it says that $N_o$ is the original l... |
I know that when you have $\ce{HCl}$, $\ce{H2O}$, and $\ce{NaOH}$ that you produce $\ce{H2O}$ and $\ce{NaCl}$.
However some people say water does react and so would think that this 2 step reaction is correct and the 1 step reaction is wrong.
$\ce{HCl + H2O + NaOH -> H3O+ + Cl- + NaOH -> 2 H2O + NaCl}$
However ... |
Water reacts or doesn't react? |
why the melting point p-toluenesulfonic acid monohydrate higher than p-toluenesulfonic acid anhydrous? But the melting point of Benzenesulfonic acid hydrate lower than Benzenesulfonic acid anhydrous? |
Why is the melting point of p-toluenesulfonic acid monohydrate higher than that of anhydrous p-toluenesulfonic acid?
Compare for example the melting point of benzenesulfonic acid hydrate, which is lower than for anhydrous benzenesulfonic acid. |
Why is the melting point of p-toluenesulfonic acid monohydrate higher than that of anhydrous p-toluenesulfonic acid? |
Why do we only consider the $\mathrm{p}K_\text{a}$ value of a drug regardless of whether it is an acid or base? Why do we not use the $\mathrm{p}K_\text{b}$ value?
|
What is the importance of using a pKa value instead of a pKb value when describing drug chemistry? |
On the acid catalysed hydration of allene, acetone is obtained as the major product. This is because of electrophilic addition of H+ across a double bond to give a vinyl carbocation, and subsequent addition of water and then tautomerism to yield ketone. What I'm confused about is that why does not an allyl carbocation ... |
Your calculations of the double bond equivalents seems correct, and there is also another hint towards a $\ce{C=O}$ double bond: the corresponding $\ce{^{13}C}$ chemical shift.
Also, while it says you have $\ce{^1H}$ decoupled $\ce{^{13}C}$ data, this is clearly wrong, because they’re showing you multiplets. The $\c... |
What is a non-classical carbocation?
How is it different from a classical carbocation (if that means something)? I am confused as I have come across this term many a times on CSE but there seems to be nothing of my level of understanding on the Internet! |
What is a non-classical carbocation? |
I did a lab about spectrophotometry and right now I need the molar absorptivity(ε) of thymol blue in acidic solution and also in basic solution. I have tried looking online but I haven't found the data I need.
What is the molar absorptivity of thymol blue in acidic solution and in basic solution?
**information**
... |
Rearranging the Eyring equation leads to the following:
$$\Delta^\ddagger S^\circ = R \ln{\frac{k \times h}{{k_\text{B}}{T}}}+\frac{\Delta^\ddagger H^\circ}{T}$$
where $k$ is the rate constant, $h$ is the Planck constant, $R$ is the universal gas constant, $k_\text{B}$ is the Boltzmann constant, $T$ is temperatur... |
What is the correct nomenclature for $\ce{CN^-}$ and $\ce{Cl^-}$ ligands in coordination compounds?
[Wikipedia][3] says the coding name(?) as cyanido and chlorido while [this][1] suggests cyano and chloro.
[1]: http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Coordination_Chemistry/Basics_of_... |
I have the absorption spectrum of a specific phycobiliprotein. Its maximum wavelength is 620.6 (nm),this is the only data I have. How can I know what type of phycobiliprotein it is? |
I've been taking an chemistry class online (for fun only) and one of the questions in the homework threw me a bit. Here's the wording:
"Draw the Lewis structure for a nitrogen atom attached to. two methyl groups (CH3) and one oxygen atom."
OK, so I know that NO is a free radical due to the odd combined valence, i... |
Lewis Structure on (CH3)2NO? |
Here is a picture of a "classical" carbocation, there is an electron deficient carbon bearing a positive charge.
![enter image description here][1]
There are many examples of "non-classical" carbocations, but the [2-norbornyl carbocation][2] is among the best known.
![enter image description here][3]
([imag... |
What is a non-classical carbocation? How is it different from a classical carbocation? I am confused as I have come across this term many times on CSE but there seems to be nothing for my level of understanding on the Internet! |
In the acid catalysed hydration of allene, acetone is obtained as the major product. This is because of electrophilic addition of $\ce{H+}$ across a double bond to give a vinyl carbocation, and subsequent addition of water and then tautomerism to yield the ketone. What I'm confused about is that why does not an allyl c... |
If the longest carbon chain is symmetric numbering-wise (meaning the numbering schemes are identical both ways) and has all alkyl substituents, should one prioritize the largest alkyl group? |
The textbook answer for why water can't mix with oil is to use the rule 'like dissolves like'. But a rule in science is none other than summarizing a few collected facts. Answering a question with a rule is like pointing a single fact - why water can't mix with oil - to a collection of facts instead. This easily invite... |
Why signals of carbon and hydrogen atoms (in NMR spectra) are split by coupling to $\ce{^{19}F}$? Some spectra books only states that
>$\ce{^{19}F}$ (natural abundance 100%) has a spin quantum number *I* of ½. The signals of carbon and H atoms up to a distance of about four bonds are split by coupling to $\ce{^{19}F}... |
Why are signals of carbon and hydrogen atoms (in NMR spectra) split by coupling to 19F? |
Here is a picture of a "classical" carbocation, there is an electron deficient carbon bearing a positive charge.
![enter image description here][1]
There are many examples of "non-classical" carbocations, but the [2-norbornyl carbocation][2] is among the best known.
![enter image description here][3]
([imag... |
I've been taking an chemistry class online (for fun only) and one of the questions in the homework threw me a bit. Here's the wording:
"Draw the Lewis structure for a nitrogen atom attached to. two methyl groups ($\ce{CH3}$) and one oxygen atom."
OK, so I know that $\ce{NO}$ is a free radical due to the odd combi... |
The $\mathrm{p}K_\text{a}$ is the $-\log_{10}$ of the $K_\text{a}$ value for the disassociation of an acid. So how do you get a $\mathrm{p}K_\text{a}$ value for a base? The base produces no hydrogen ions so can’t you only have a $\mathrm{p}K_\text{b}$? |
Here is a picture of a "classical" carbocation, there is an electron deficient carbon bearing a positive charge.
![enter image description here][1]
There are many examples of "non-classical" carbocations, but the [2-norbornyl carbocation][2] is among the best known.
![enter image description here][3]
([imag... |
Your calculations of the double bond equivalents seems correct, and there is also another hint towards a $\ce{C=O}$ double bond: the corresponding $\ce{^{13}C}$ chemical shift.
Also, while it says you have $\ce{^1H}$ decoupled $\ce{^{13}C}$ data, this is clearly wrong, because they’re showing you multiplets. The $\c... |
I've been taking an chemistry class online (for fun only) and one of the questions in the homework threw me a bit. Here's the wording:
"Draw the Lewis structure for a nitrogen atom attached to. two methyl groups ($\ce{CH3}$) and one oxygen atom."
OK, so I know that $\ce{NO}$ is a free radical due to the odd combi... |
Valence electrons experience an electrostatic force from the nucleus. The nucleus has its character positive charge, but due to *[shielding][1]* by core electrons the total positive charge is not completely felt by the electrons, so the actual net positive charge felt by the valence electron has its own name and is cal... |
Valence electrons experience an electrostatic force from the nucleus. The nucleus has its character positive charge, but due to *[shielding][1]* by core electrons the total positive charge is not completely felt by the electrons, so the actual net positive charge felt by the valence electron has its own name and is cal... |
Part (a)
I agree with the previous comments that a Wittig reaction is the best way forwards especially in terms of regioselectivity of the double bond. PPh3, MeI and NaH would be an excellent combination. Perhaps draw the mechanism and you'll see how/why this work so well?
If you are interested, you could use (Cp... |
What things become crystals? |
My friend is installing copper pipes in his house, which is going to be in a humid area, and he says that copper will only be oxidized by the air and the excess water vapor in the humid air won't affect it. However, it is to my understanding that since water vapor is H2O, which contains oxygen, there will be more oxida... |
Does water vapor in the air oxidize copper? |
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