Questions tagged [aldol-reaction]

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

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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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47 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 ...
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33 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 ...
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2answers
203 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 ...
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0answers
129 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 ...
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1answer
112 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 ...
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1answer
40 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, $\...
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1answer
387 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 ...
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2answers
165 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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1answer
146 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 ...
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2answers
236 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 ...
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217 views

Predict the aldol condenation product given IR and H-NMR spectra

An aldol condensation product would have a ketone and at least one alkene in the form of R1-C(=O)-C(R2)=C(R3)-R4 H-NMR: 7.09ppm 1H doublet, 7.42ppm 3H triplet, 7.64ppm 2H quartet, 7.75ppm 1H doublet. ...
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1answer
194 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 ...
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1answer
165 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:...
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945 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 ...
6
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1answer
109 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 ...
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62 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
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1answer
460 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 ...
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2k 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 ...
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1answer
114 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?
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1answer
241 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 ...
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2answers
414 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 ...
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61 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 ...
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188 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?
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413 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 ...
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320 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 ...
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1answer
479 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 ...
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334 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 & ...
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1answer
87 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 ...
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172 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 ...
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92 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 $\ce{OH-}$...
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439 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{...
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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.
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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 ...
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1answer
691 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 ...
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7k 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:
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2answers
2k 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 ...
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287 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 ...
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866 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 ...
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210 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 ...
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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 ...
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3answers
360 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 ...
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1answer
2k views

Does aldol condensation give different products in different conditions?

I know the mechanism of aldol condensation and general method to determine products in crossed aldol reactions, or reactions between dissimilar molecules. But the following statement in my class notes ...
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1answer
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Selectivity in aldol condensation between pivaldehyde and acetone

In a crossed aldol condensation (condensation between aldehyde and a ketone), the primary products are such, that the carbonyl group of the ketone remains intact, and the $\alpha$-hydrogen of ketone ...
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What is the product formed in the reaction of dimedone and benzaldehyde?

I'm having a hard time deducing the structure of the product formed when dimedone and benzaldehyde react in the presence of catalytic piperidine. I think that a Knoevenagel reaction will get me to ...