12
votes
Accepted
Monoepoxidation of 1,2-dimethylcyclohexa-1,4-diene using m-CPBA
The interaction of the alkene with m-CPBA is primarily nucleophilic/electrophilic in nature, i.e. the π MO of the alkene attacks the O–O σ* orbital. Therefore, the more electron-rich alkene (i.e. more ...
- 71.9k
8
votes
m-CPBA Selectivity between Baeyer Villiger Oxidation and Epoxidation?
The answer appears to be "it depends" (perhaps this should not surprise an experienced organic chemist).
According to the abstract of the paper by Mendelovici and Glotter [1] in steroid chemistry:
...
- 23k
8
votes
Why does the Rosenmund reduction stop at the aldehyde stage?
In general, the Rosenmund reduction isn't actually used very often, mainly since the catalyst is also very good at reducing other functional groups which may be present in the molecule (the catalyst ...
- 17.2k
6
votes
Accepted
Why is a Grignard reagent not protonated by chloramine?
The $\ce{N-H}$ protons are relatively weakly acidic and this makes deprotonation kinetically less favored if an alternative nucleophilic attack mechanism is available. With $\ce{NH3}$ no such ...
- 62.6k
6
votes
Accepted
Will a Grignard reagent react with an epoxide or episulfide first?
There are quite a few reasons why the episulfide might open before the epoxide:
Sulphur is less electronegative than oxygen. Therefore, by Bent's rule , more atomic s-character will be directed by ...
- 3,226
5
votes
m-CPBA Selectivity between Baeyer Villiger Oxidation and Epoxidation?
The selective Baeyer-Villiger Oxidation of unsaturated ketones is definitely depends on the conditions used. I do not want to eloborate this fact any further because it was well documented in ...
- 42.1k
5
votes
Accepted
Reaction of hydrazine and hydroxylamines with carboxylic acids
For simplicity, I will consider the reaction of acetic acid with ammonia, because the same principles apply. The two alternatives are:
$$
\underbrace{\ce{CH3C(O)NH2}}_{\mathrm{amide}} + \ce{H2O} \...
- 7,039
4
votes
Accepted
Single electron reduction of ketone by Na or Zn
Let the carbonyl compound under consideration be acetone.
Case I: Hydrogen Abstraction
The species formed are NaH and an allyl-type radical. The resonating system includes an electronegative oxygen ...
- 1,526
4
votes
Will a Grignard reagent react with an epoxide or episulfide first?
I'm not sure I buy the strain argument either. Is there enough difference between the reactivities that you would get selectivity? In the real world I think you would get a mixture, possible complex ...
- 23k
3
votes
Accepted
Are alkenes or alkynes reduced first with diimide?
Your given answer to the textbook question is seemingly correct. I said seemingly, because this reaction is not well understood to date, even though its first introduction was given at time as far as ...
- 42.1k
3
votes
Why does magnesium prefer to insert into C–Br bonds over C–Cl bonds?
As noted earlier, the determining factor is the greater strength of the carbon-chlorine bond versus carbon-bromine, which leads to a higher activation energy for the magnesium to react with the former....
- 62.6k
3
votes
Accepted
Can an ether be selectively hydrolysed in the presence of an ester?
There are certain ethers which are somewhat easier to remove than others. If you stipulate that the ether must have a CH2 group immediately adjacent to oxygen, then a couple of possibilities, off the ...
- 71.9k
3
votes
Why does bromine add to a double bond instead of a triple bond if both are present?
I'm going to take "more reactive" as in the alkene undergoes bromination at a faster rate than the alkyne, which seems to imply that the activation energy of the transition state is greater.
A ...
- 226
2
votes
How can an aromatic ketone be reduced in the presence of a nitro group?
A discussion about alternative reduction methods was here Clemmensen reduction vs. Wolff-Kishner reduction. I've not seen nitro groups reduced by the acid-triethylsilane or tetramethyldisiloxane ...
- 2,221
2
votes
nBuLi and tBuLi can take part in halogen metal exchange OR deprotonate. Is there any way to predict which it favours?
According to Bordwell $\mathrm{p}K_\mathrm{a}$ Table, $\mathrm{p}K_\mathrm{a}$ of $\ce{PhCH2COSPh}$ is $16.9$, which is compatible with alcoholic $\ce{OH}$. We all know that Grignard reagents and ...
- 42.1k
2
votes
Performing a reaction on one side of piperazine ring
Making your own BOC piperazine is not hard, the general principle is to do the reaction with the monohydrochloride - there is a good procedure here from piperazine, piperazine di-HCl, t-BuOH and ...
- 23k
1
vote
Can organocuprates do SN2 reactions with tosylates?
Cuprates (also known as Gilman reagents) do not generally react with isolated ketones. If they did the widely used reaction of cuprates with alpha/beta unsaturated ketone would not work to give the ...
- 23k
1
vote
Accepted
Why is the nitrile group not hydrolyzed as well during hydrolysis of imine in Thorpe reaction?
It has to do with hybridization. The nitrogen in a nitrile is sp hybridized; imine sp2 and ammonia sp3. The more s-character in hybrid orbitals, the less basic the electron pair (protonated nitrile ...
- 17.5k
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