Questions tagged [aldol-reaction]

This tag should be applied to questions about mechanisms, selectivity, or other aspects of aldol reactions.

Filter by
Sorted by
Tagged with
-2
votes
0answers
41 views

During of Formation of aldol why Enolate ion react from carbon double bond end even though carbonyl group is a hard electrophile

When we are reacting 2 moles of an aldehyde /ketone ( with alpha H ) with OH- as base to form aldol first step is formation of Enolate ion by reaction of OH- with acidic alpha H, second step is ...
2
votes
0answers
23 views

Sn(II) compound stereoselectivity in aldol reactions

In "advanced organic chemistry: part B" fifth edition, page:130, the authors state that chiral proline-like additives to Sn(II) compounds can further increase stereoselectivity of aldol ...
0
votes
0answers
41 views

Dehydration of aldol

In my book it is written that to dehydrate an aldol the product of aldol condensation is heated in an iodine environment. But what is the role of Iodine here and how does it catalyse the dehydration ...
0
votes
2answers
81 views

Acidity of alpha hydrogens in enolate formation

I am interested in why the most right alpha hydrogen is removed to form the carbanion prior to intermolecular aldol condensation (2nd row first molecule). Why is it that the alpha hydrogen from the ...
4
votes
1answer
163 views

What is the correct reaction mechanism?

I came across this question: I propose two things to happen: It can undergo Aldol condensation or it can undergo SN by replacing $\ce{-Cl}$ with $\ce{-OH}$. But apparently, both these mechanism ...
0
votes
1answer
54 views

Effect of +I on the alpha hydrogen in aldol reaction [duplicate]

We have $\ce{(CH3)2CHCHO}$. Is the alpha-hydrogen acidic enough to react with a base? There is +I effect of two methyl groups, however there the carbanion is getting stabilised through resonance. And, ...
4
votes
0answers
40 views

Why is the reverse aldol cleavage of fructose 1,6-bisphosphate highly endergonic under standard conditions?

I have another question similar to this one. I just don't have intuition for why reactions are thermodynamically favorable or unfavorable and I'd like to build it. This time I'd like to ask about ...
1
vote
1answer
101 views

Decide major product for first order elimination reaction

This is my own created question. The favourable thing for (c) to be a major product is conjugation of double bonds and highly acidic nature of hydrogen (resulting in elimination of hydrogen at a ...
3
votes
0answers
38 views

The safest and easiest way of working with solid LDA

I have a 25-gram bottle of solid LDA (lithium diisopropylamide), factory sealed. I'm going to setup an aldol reaction with it, but I don't know how to organize work properly. I think of quickly ...
0
votes
0answers
13 views

Can aldol reaction using Evan's auxiliary yield diastereoselective products for ketone substrates?

Evan's diastereoselective aldol reaction commonly uses aldehyde as a substrate and I have never come across an example that uses ketone yet.
0
votes
0answers
49 views

Aldol Condensation Product selection

It is known that the enol form double bond tends to attack the electrophilic carbon centre in an aldol reaction. But what will be the majour product in this reaction. The latter one may be enol attack ...
1
vote
0answers
62 views

Can Diels-Alder reaction occur using reagents of Robinson annulation?

Robinson annulation seemed somewhat like the Diels-Alder reaction to me, if all ketonic groups were to be represented as enol then cyclohexanone would be like diene and the Michael acceptor as a ...
8
votes
2answers
3k views

What does the intramolecular aldol condensation of 6-oxoheptanal form?

I know that when 6-oxoheptanal is treated with NaOH, an intramolecular aldol condensation will take place. But will a five-membered ring or seven-membered ring be formed? I know that the five-...
0
votes
1answer
76 views

What would be the aldol condensation products in B

In this question (13) I figured out A,C were wrong and D would be correct choice but I am stuck at finding out products formed in B and also why it would be wrong? Please help.
0
votes
0answers
66 views

Does 1,3-diphenylprop-2-en-1-one give a positive Tollens test?

If we have 1,3-diphenylprop-2-en-1-one, will it give positive Tollens test? I think aldol reactions are reversible under basic conditions. Here there are mildly basic conditions, so will we get back ...
0
votes
1answer
435 views

How would I synthesize ethyl 2‐oxocyclohexane‐1‐carboxylate from cyclohexanone? [closed]

I thought the 1st step would be deprotonation of a H atom to form the enolate. Then an aldol reaction, but the product I end up with is the alcohol, not the ketone.
-3
votes
1answer
188 views

How to avoid cannizaro reaction during aldol reaction? [closed]

I am doing some Aldol reaction in lab,problem is **basically one of my Aldehyde is converting largely in cannizzaro products.**Please suggest me which base I can use so that I will not get cannizzaro ...
0
votes
0answers
56 views

Will cyclopenta-2,4-dienecarbaldehyde undergo aldol condensation or cannizzaro reaction?

The following question was given in an exam.Which of the following undergo aldol condensation ? Given answer : a,b,c My answer: b,c My Logic : Cyclopenta-2,4-dienecarbaldehyde(1) on reaction with ...
1
vote
0answers
41 views

Aldol Reaction on an intermediate

I was given the following reaction to prove a mechanism for: and I managed to prove the first step with ease. The second step, forming the "base-catalysed aldol" is the part that's rather confusing ...
2
votes
2answers
872 views

Does 4-methylbenzaldehyde give haloform and aldol reactions?

The following question was asked in JEE Advanced 2017: The answers given are option A and B. I was able to get B as the correct answer but A look like the wrong option to me. My approach for ...
1
vote
0answers
451 views

1,4-addition vs 1,2-addition aldol/aldol type reactions

In the aldol/cross aldol reaction, of $α,β$-unsaturated carbonyl compound, under what circumstances does a 1,2-addition i.e. aldol condensation (carbanion formed directly attacking carbon of carbonyl ...
1
vote
1answer
268 views

How can one distinguish an IR spectroscopy alcohol band on an organic molecule versus the alcohol bands from water in the sample?

I'm reading this IR spectra and trying to determine if the large broad band at 3388 is alcohol from an intermediate or from water in the sample. The details of the reaction, conditions, and mechanism ...
0
votes
1answer
50 views

Aldehyde and ketone reactions

Reagents to carry out above conversion, P, Q, R respectively are: (a) $\ce{H2C=CH-CH2-Br}$, $(\ce{HO-})$, $[\ce{HO-}, Δ]$, Wacker process. (b) $\ce{H2C=CH-CH2-Br(HO^-)}$, Wacker process, $\ce{HO-}$, $...
4
votes
1answer
4k views

Determination of major product in crossed aldol condensation

The title speaks for itself really. I know that if we have a conventional ketone (with 3+ α-hydrogens) and an aldehyde with less than or equal to 3 α-hydrogens, the ketone acts as the nucleophile and ...
1
vote
2answers
420 views

Acetone Enolate-HaloBenzene Reaction

A reaction I am trying to perform says to use a strong base like Sodium Amide with Acetone and Iodo-Benzene as reactants with DMSO as the solvent to form Phenylacetone. The main idea is to use the ...
1
vote
1answer
221 views

What reaction takes place here? [duplicate]

Upon reading the given question, I realized that: The first reaction is an aldol condensation reaction between the given compound and formaldehyde. So the product after 1st step is: Now, the ...
4
votes
2answers
790 views

How does dehydration of an alcohol occur in alkaline medium?

During aldol condensation reaction the aldol formed reacts further to give alkene (which is probably called enone) I am really struggling with this part of the reaction as my textbook says nothing ...
2
votes
1answer
726 views

Reduction using hydrazine and glycol in alkaline medium

Question: This question was asked in my exam and I have done it properly until the third step. Unfortunately, although the last step looked like Wolff-Kishner reduction to me, I could not do it. My ...
-1
votes
1answer
774 views

Why is the carbanion resonance structure being used in the aldol condensation mechanism?

In the above mechanism's first step, what motivates the use of the carbanion resonance structure of the enolate ion if the negative charge is better localized on the more electronegative oxygen? Edit:...
5
votes
1answer
2k views

Major product for aldol condensation between acetophenone and acetaldehyde

Crossed aldol condensation is done between acetaldehyde and acetophenone by using NaOH as the base. So, here we can get 4 possible products. But which one would be the major? I know that acetaldehyde ...
7
votes
1answer
228 views

How does this ring expansion on a steroid system occur?

The correct answer is supposedly B, as shown by Gravestock et al.[1] In this reaction after ozonolysis of the C=C double bond, two ketones are formed. How is a rearrangement or expansion of the ring ...
3
votes
0answers
183 views

Claisen-like condensation with acid chloride

In the Claisen condensation, an ester enolate attacks an ester, with an alkoxide anion leaving subsequently to give a $\beta$-keto ester. Is it possible for a typical enolate of an aldehyde or ketone ...
4
votes
1answer
1k views

Why cyclohexane-1,4-dicarbaldehyde does not give aldol condensation?

I was recently came to know as a fact that cyclohexane-1,4-dicarbaldehyde does not give the aldol condensation reaction in spite of possessing α-hydrogens. I was told that this is due to steric ...
0
votes
0answers
5k views

P2NP synthesis ammonium acetate catalyst?

I am going to try to prepare some P2NP from benzaldehyde and nitroethane following this procedure: The aldehyde (5g), 5 ml. of the nitroalkane, and 2g of ammonium acetate were added to 20 ml of ...
0
votes
1answer
219 views

Aldol Condensation with Cyclic Molecule [closed]

How does one solve this mechanism? Why doesn't the negatively charged oxygen on the non-cyclic molecule remove an alpha hydrogen from the cyclic one?
9
votes
2answers
376 views

Selectivity in aldol condensation of 7-oxo(6,6-²H₂)octanal

I am supposed to find the product of the following reaction: I know that six-membered rings are more stable than five-membered rings, but the C-D bonds are stronger, so it confuses me where will the ...
0
votes
2answers
856 views

Product of an intramolecular aldol condensation

When nonane-2,8-dione is treated with base, the product 1-(2-methylcyclopent-1-en-1-yl)ethan-1-one forms according to the following scheme: The arrow denotes the hydrogen that is first attacked by the ...
1
vote
1answer
76 views

Is one syn aldol product preferentially formed over the other?

In Carruthers' Modern Methods of Organic Synthesis, the following aldol reactions of two (Z)-enolates with benzaldehyde are shown: The two transition states shown seem to be different, and lead to ...
5
votes
1answer
344 views

Base-promoted rearrangement of β-ketoester

Propose a reasonable mechanism for the following transformation: I guess an enolate probably forms first, but then what does it attack to give something like the product in the question?
4
votes
1answer
2k views

Acidity of aldehydes and ketones and enolate formation

In most academic courses you'd learn that aldehydes are more acidic (lower $\text{p}K_\text{a}$) than ketones due to the lower electron donating effect of the proton compared to the alkyl group of the ...
-1
votes
2answers
587 views

Which Alpha-H will be extracted in intramolecular condensation rxn between ester and ketone

In this problem, which hydrogen will be extracted - the one near the ketone group (Marked 2) or the one near the ester (Marked 1)? My approach:- In intramolecular reactions between aldehydes and ...
6
votes
1answer
1k views

Regioselectivity in Claisen condensation and aldol reaction

I'm having a hard time determining regio-selectivity in those two reactions. At the image above I've drawn one example for each on of them. My question is how do we choose where the deprotonation ...
8
votes
0answers
536 views

Why are lithium (Z)-enolates more stereoselective than (E)-enolates in aldol reactions?

In aldol reactions, it is apparently a general rule of thumb that (Z)-enolates give higher stereoselectivity (for the syn aldol product) than (E)-enolates do for the anti product. Quoting Carey & ...
0
votes
1answer
114 views

Deciding which α-Η gets abstracted in aldol condensation

Consider the base catalysed aldol condensation of methyl ethyl ketone. The first step involves the abstraction of a proton by the base. However I am having trouble deciding whether the proton will be ...
6
votes
1answer
280 views

Chelation-controlled aldol: why is the α substituent pseudo-axial?

In this Mukaiyama aldol reaction, taken from a 1999 paper by D.A. Evans,1 when $\ce{TiCl4}$ was used as the Lewis acid catalyst, the aldehyde 4a formed a chelated intermediate whereas 4b did not (due ...
3
votes
0answers
118 views

Can aldol reaction occur during α-halogenation of ketone?

I know both aldol and $\alpha$-halogenation reaction well. I know that in and aldol reaction, the carbonyl containing molecules like ketones and aldehydes attacks themselves when base like $\ce{OH-}$...
0
votes
1answer
561 views

What products did this aldol condensation create?

I followed a procedure in my organic chemistry lab, but I don't understand what product the procedure created. Can someone tell me what chemicals reacts with which to create the product? First $\ce{...
7
votes
2answers
3k views

Will cinnamaldehyde undergo self-aldol condensation?

Will cinnamaldehyde undergo self-aldol condensation? My book says it won't, but since it has an α-hydrogen, I'm confused.
4
votes
2answers
331 views

Regioselectivity of deprotonation of 1,4-dicarbonyl

In the intramolecular aldol condensation of hexane-2,4-dione (above), why does the base abstract one of the $\ce{-CH3}$ protons instead of one of the $\ce{-CH2}$ protons? Both sets of protons are α to ...
3
votes
1answer
1k views

Will 2-methylbutanal undergo aldol condensation

Will 2-methylbutanal undergo aldol condensation? We are taught that it will not because the +I effect makes the carbanion unstable, but if we make an enolate ion, isn't it resonance stabilized by the ...