Carbonyls

Question 1

Outline two tests for carbonyls

Answer 1

Brady’s reagent - where 2,4-DNP is dissolved in methanol and sulfuric acid. It tests for all carbonyls, and a positive result will give an orange precipitate.
Tollen’s reagent - AgNO3(aq) in dilute ammonia. This only tests for aldehydes and will produce a silver mirror.

Question 2

Nucleophilic addition with NaBH4 creates

Answer 2

Alcohols

Question 3

Nucleophilic addition with hydrogen cyanide (made in situ) creates

Answer 3

hydroxynitriles

Question 4

Are halogen substituted carboxylic acids stronger or weaker?

Answer 4

Stronger, as the halogens withdraw electron density, so make it easier for the hydrogen to be lost.

Question 5

How are acyl chlorides produced?

Answer 5

A carboxylic acid is reacted with anhydrous SOCl2, with products HCl and SO2, both gases.

Question 6

How are acid anhydrides synthesised?

Answer 6

A carboxylate salt is reacted with an acyl chloride under anhydrous conditions.

Question 7

What are the pros and cons of using acyl chlorides in esterification?

Answer 7

The yield is much higher as the reaction goes to completion, but HCl gas is produced in the process.