Ketone from acid chloride and cuprate: practice and mechanism
The cuprate replaces the Cl of the acid chloride by CH₃ and stops at the ketone, because it hardly reacts with ketones.
Example
Cuprates are less reactive than Grignard reagents: they replace the chloride of the acid chloride by a methyl group but do not attack the ketone formed. The reaction therefore stops at the ketone instead of the tertiary alcohol.
Mechanism step by step
- 1
The cuprate transfers a methyl group to the carbonyl carbon of the acid chloride (often via a copper(III) intermediate).
- 2
Chloride leaves and the ketone forms.
- 3
At −78 °C the cuprate does not react with the ketone; the reaction stops.
Practice tasks
Which product forms, which reagent is needed? After each answer you see the explanation.
Which main product forms?
Typical mistakes
- That would be the Grignard product (two additions). Cuprates do not react further with the ketone formed.
- Hydrolysis to the acid would be the reaction with water. Here the cuprate transfers a methyl group.
Often confused with: Grignard reaction · Ester from acyl chloride
Frequently asked questions
What other routes to ketones are there?
Nitrile + Grignard, Weinreb amide + Grignard, Friedel–Crafts acylation (aryl ketones) and oxidation of secondary alcohols.
Why does Grignard react twice?
The ketone is reactive and still present in the mixture, so a second Grignard adds and gives the tertiary alcohol.