Chapter 22 - Enolate Chemistry Flashcards
Alkylation of an enamine generates what kind of product?
A ketone with the alkyl group on the less-substituted a-carbon.
A ketone is reacted with what type of amine to form an enamine?
A secondary amine
Why does Keto-Enol tautomerization cause a mixture of cis and trans products?
A chiral carbon loses its stereochemistry when it is in the enol form, so an alpha proton can return to the carbon at either angle.
In equillibrium deprotonation, how does the reaction end up going to the products if the ketone is the preferred form (over the enolate?) What problem arises from this?
The enolate is slowly consumed when it reacts with an electrophile, which pushes to reaction to the right to form more enolate? The problem is that the base used to deport ate can also react with the electrophile, which is wny we use LDA.
What is the expected product of enolate alkylation using LDA?
Alkyl group attaches to less-substituted alpha carbon
Why is dehydration of the Aldol favorable?
B/c it leads to a stable, conjugated product, which drives the whole condensation.
In a crossed Aldol condensation, why is it necessary to have only one carbonyl with alpha hydrogens?
B/c otherwise we will get a mixture of products from variation in which carbonyl becomes the enclave and attacks the other.
What is one molecular that could be used for crossed Aldol?
Benzaldehyde - no alpha protons.
What occurs when a ketone is treated with X2 in basic conditions?
Multiple halogenation followed by haloform reaction.
What is the product of a ketone treated with Br2 in acidic conditions?
Mono-substituted bromoketone.
What size range of rings is possible to make with a dicarbonyl?
5-6 due to ring strain or entropy of other ring sizes.
Which has more acidic protons; a ketone or an ester?
How about a ketone and a B-Keto ester?
- Ketone
- B-ketoester
What drives the claisen condensation?
Deprotonation of the B-keto ester product forms a very stable enolate ion.
What is important about the base used in claisen condensation?
The OR group should match that of the ester.
