Enolates and aldols

Question 1

Aldols

Answer 1

An aldol is a compound with both an aldehyde and an alcohol.

Aldol condensation reactions are important reactions where an aldehyde/ketone acts as both an electrophile (keto form) and a nucleophile (enol form)

Question 2

Aldols

Aldol addition

Answer 2

First step of aldol condensation:
Nucleophile, an enol form aldehyde/ketone + electrophile, which is keto form aldehyde/ketone.
Creates a C-C bond.

Question 3

Aldols

Dehydration

Answer 3

Second step of aldol condensation is dehydration (loss of water), which creates an enone with a double bond

Question 4

Aldols

Retro-aldol reactions

Answer 4

Reverse aldol reaction. Cleavage of bond between alpha and beta carbon. Seen in glycolysis.

Question 5

Enols

Keto/enol tautomerization

Answer 5

Aldehydes and ketones have keto and enol isomer forms.
The enol form has the double bond and hydrogen switched.
The keto form is more stable and common.

Question 6

Enols

Enolates

Answer 6

An anion formed by the removal of an α-hydrogen via reaction with a base from the enol form of aldehyde/ketone, stabilized by resonance.
This form is more nucleophilic but less stable.

Question 7

Enols

Kinetic and thermodynamic enolates

Answer 7

Kinetic is favored at low temperatures with strong bases with faster reactions.
Thermodynamic is favored at high temperatures with weak bases with slower, irreversible reactions.