Questions tagged [aldol-reaction]

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

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Benzoin condensation, byproducts [closed]

I have read that some byproducts appear during benzoin condensation catalysed by thiamine and sodium hydroxide. What are they?
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Various pathways of an alpha diketone reaction

This is a question from JEE Advanced 1997. I have found two possible products of the reaction: By intramolecular aldol condensation: By benzil-benzilic acid type rearrangement: Which reaction takes ...
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What is the mechanism of aldol condensation between two diketo-compounds with sodium bicarbonate?

In particular, what is the mechanism of aldol condensation of dimethyl-1,3-acetonedicarboxylate and 2,3-butanedione with sodium bicarbonate? I'm trying to work out the mechanism of this aldol ...
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When does the Mukaiyama-Addition follow which transition state and how does it affect the stereochemistry?

in the course on enantioselective organocatalysis, we discussed the route to hexoses via organocatalytic aldol addition and subsequent Mukaiyama addition. The use of either TiCl4 or MgBr2 leads to ...
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Aldol Cyclization Cascade Reaction between Two Ketones in Basic Alcoholic Solution

My professor gave a hint that the reaction scheme is a multiple carbonyl reaction which involves cyclization. He emphasizes that the reactivity of carbonyl compound in terms of C-H acidity and ...
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What is the condition to have a schiff base precipitate for sulfonamides?

In the sulfonamides group we observe that some category (like sulfanilamide, sulfamethizol) gives products of condensation with carbonyl so a precipitate, whereas other category (like sulfaguanine, ...
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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 ...
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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 ...
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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 ...
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4 votes
1 answer
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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 ...
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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, ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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-...
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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.
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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 ...
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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.
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1 answer
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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 ...
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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 ...
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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 ...
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2 votes
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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 ...
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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 ...
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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 ...
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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, $\ce{HO-}$, $...
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6 votes
1 answer
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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 ...
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1 vote
2 answers
457 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 ...
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1 answer
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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 ...
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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 ...
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2 votes
1 answer
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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 ...
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-1 votes
1 answer
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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:...
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5 votes
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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 ...
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7 votes
1 answer
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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 ...
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3 votes
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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 ...
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4 votes
1 answer
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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 ...
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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 ...
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1 answer
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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?
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8 votes
2 answers
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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 ...
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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 ...
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1 vote
1 answer
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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 ...
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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?
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1 answer
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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 ...
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-1 votes
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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 ...
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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 ...
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8 votes
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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 & ...
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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 ...
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6 votes
1 answer
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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 ...
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3 votes
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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 $\ce{OH-}$...
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