F324 - Carbonyl Compounds

Question 0

Aldehydes can be made by oxidising what type of alcohol? Include the conditions and reagents needed.

Answer 0

Primary alcohols
Acidified dichromate
Distillation

Question 1

Aldehydes and ketones contain what functional group?

Answer 1

Carbonyl functional group

Question 2

Ketones can be made from oxidising what type of alcohol? Include the conditions and reagents needed.

Answer 2

Secondary alcohol

Acidified dichromate

Question 3

Describe the colour change of acidified dichromate.

Answer 3

Orange to green

Question 4

Carbonyl compounds can be reduced back to alcohols using what reducing agent?

Answer 4

NaBH4

Question 5

What is a nucleophile?

Answer 5

An electron pair donor

Question 6

Describe a test that shows the presence of an aldehyde or a ketone.

Answer 6

Brady’s reagent, 2,4-dnph, is added to aldehyde or ketone; a deep yellow or orange precipitate is made if the compound is an aldehyde or a ketone; solid product is impure so recrystallise; record melting point of recrystallised solid; compare value to chemistry literature to identify original aldehyde or ketone.

Question 7

Describe a test to distinguish between an aldehyde or a ketone.

Answer 7

Use Tollens’ reagent. This can be made by adding aqueous sodium hydroxide to aqueous silver nitrate until a brown precipitate is formed; add dilute ammonia until the precipitate just dissolves; the colourless solution is the Tollens’ reagent. Add this to the unknown sample and heat; if positive for an aldehyde a silver mirror will form. This is because the silver ions in the Tollens’ reagent are reduced to silver and the aldehyde is oxidised to a carboxylic acid