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
3
votes
0answers
28 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 ...
-2
votes
0answers
15 views

Why can't the following product be formed in the given Intramolecular Aldol Condensation? [closed]

In the final step I have extracted the hydrogen from the alpha carbon, please tell me where I am wrong. Thanks
0
votes
0answers
12 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
45 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
49 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 ...
7
votes
2answers
2k 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
52 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
49 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
290 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
152 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
53 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
38 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
694 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
383 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
237 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
47 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, $\ce{HO-}$, $...
2
votes
1answer
3k 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
359 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
193 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 ...
3
votes
2answers
676 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
598 views

Reduction with NH2-NH2 , OH-, and glycol

this question was asked in my exam and I have done it properly until the very third step but unfortunately, although the last step looked like wolfkishner reduction to me I could not do it. My ...
-1
votes
1answer
520 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
202 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
148 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 ...
3
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
4k 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
194 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
350 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
754 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
71 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
303 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?
3
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
501 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
476 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
106 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
266 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
112 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
516 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{...
6
votes
2answers
2k 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
311 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 ...
2
votes
2answers
8k views

Self aldol condensation of butanal under basic conditions

The reaction is such: I've counted the number of carbons on each side: LHS=4, RHS=8 My working is such:
5
votes
2answers
4k views

Product of intramolecular aldol condensation of 3-methyloctane-2,7-dione

What is the major product formed when 3-methyloctane-2,7-dione is treated with sodium hydroxide? My main issue is where the base deprotonates. Two enolates are possible (I neglected the other ...
4
votes
2answers
402 views

Why do Zr, Sn, and Ti enolates form syn aldols selectively?

In Organic Chemistry (2nd ed.) by Clayden, Greeves, and Warren, it is stated that (p 869) [...] the enolates of some metals [Sn(II), Zr, Ti] give syn aldols regardless of enolate geometry. There ...
17
votes
1answer
1k views

Why does acetate aldol with Evans auxiliary give almost no diasteroselectivity?

The following acetate aldol reaction gives no diasteroselectivity: Because I don't know what the basis of above statement is (I heard it in a lecture and read it on some internet web pages), I expect ...
7
votes
1answer
234 views

What determines whether an aldol reaction will occur again or eliminate?

The product of an aldol reaction is a $\beta$-hydroxy ketone. This can go on to eliminate to form an alkene thus: However, the species on the far left of the above diagram (the $\beta$-hydroxy ketone ...
2
votes
0answers
136 views

Does the amine used to generate the enolate affect the selectivity of an Evans aldol reaction?

In an Evans aldol reaction, the enolate is typically generated by addition of a boron Lewis acid (e.g. $\ce{(n-Bu)2BOTf}$) and an amine, which acts as a weak base. I'd like to know whether there's any ...
6
votes
3answers
507 views

Aldol of 7-oxooctanal

I want to do intramolecular aldol condensation of 7-oxooctanal: I am talking about the major product. Clearly, a 6-membered ring would be a major product, but there are 2 possibilities: taking ...