Propeties of carboxylic acids and esters

Question 1

Are carboxylic acids soluble?

Answer 1

• the carboxylic acid group can form hydrogen bonds with water molecules
• however larger carboxylic acids cannot as the carboxylic group is deeper within the molecule
• up to 4 carbon chain

Question 2

describe the melting point of carboxlyic acids?

Answer 2

• much higher melting points than alkanes of a similar Mr
• this is because they can form hydrogen bonds between one another

Question 3

How are carboxylic acids identified?

Answer 3

• measure its melting point and compare it with tables of known melting points
• A Thiele tube amy be used or found electrically

Question 4

What are esters?

Answer 4

derived from carboxylic acids

the -OH group of the acid is replaced by a hydrocarbon group

Question 5

What is the general formula of an ester?

Answer 5

RCOOR’

Question 6

How are esters named?

Answer 6

• based on that of the parent acids
• e.g. esters from ethanoiuc acid are called ethanoates
• the name always begins with the alkyl (or aryl) group that has replaced the hydorgen of the acid
• e.g. methyl ethanoate

Question 7

What are the properties of ester and uses of short chain esters?

Answer 7

• fairly volatile
• pleasent, fruity smells
• flavouring and perfume
• e.g. octyl ethanoate is orange flavoured
• also used as solvent and plasticisers
• fats and oils are esters with longer carbon chains