carboxylic acids

Question 1

Carboxylic acids are organic compounds identified by the functional group…

Answer 1

-COOH

Question 2

the functional group -COOH contains…

Answer 2

a carbonyl group (C=0) and an -OH acid group

Question 3

When naming carboxylic acids, the suffix …. is used.

Answer 3

-anoic acid

Question 4

what are 3 ways that carboxylic acids are prepared ?

Answer 4

• Carboxylic acids can be prepared by the oxidation of primary alcohols or aldehydes under reflux.
• Acidified potassium dichromate(VI) is commonly used as the oxidising agent.
• They can also be produced by the hydrolysis of nitrile compounds.

Question 5

are carboxylic acids soluble in water?
why?

Answer 5

• They can form hydrogen bonds with water, meaning they are soluble in water.
• As chain length increases, their solubility decreases since CH, groups do not form hydrogen bonds with water - only van der Waals forces.

Question 6

can carboxylic acid molecules form hydrogen bonds between each other?

Answer 6

The -COOH functional group allows carboxylic acid molecules to form hydrogen bonds between each other.
- with both the C=O and O-H parts of the functional group

Question 7

why are the boiling and melting points of carboxylic acids higher than those of alcohols, aldehydes and ketones?

Answer 7

Since carboxylic acids can form hydrogen bonds between molecules, with both the C=0 and
O-H parts of the functional group, their boiling and melting points are even higher than those of alcohols, aldehydes and ketones.

Question 8

how can you produce a primary alcohol from a carboxylic acid?
- type of reaction?
- nucleophile?
- conditions + why?

Answer 8

Carboxylic acids are first reduced to aldehydes. However, aldehydes can not be isolated from this reaction as they are more reactive than carboxylic acids, so they are immediately reduced further to primary alcohols

• type of reaction = reduction
• reducing agent + nucleophile = lithium tetrahydridoaluminate(III) (lithium aluminium hydride, LiAIH4) can be used to produce primary alcohols from carboxylic acids
• conditions = reaction is carried out in solvent of dry ether, this is because LiAIH4 is a very reactive compound and will react violently with water and alcohols

Question 9

neutralisation reaction with carboxylic acids (weak acid) and bases (e.g- NaOH & NH3)

Answer 9

Carboxylic acids are weak acids and therefore react with bases in a neutralisation reaction to produce a salt

e.g:
СН3COOH + NaOH → CH3COONa + H20

CH3CH2COOH + NH3 → CH3CH2COONH4