6.1.3 Carboxylic Acids And Esters

Question 1

How can carboxylic acids be formed?

Answer 1

• oxidation of primary alcohols or aldehydes under reflux
• hydrolysis of nitriles compounds

Question 2

Are carboxylic acids soluble in water?

Answer 2

• can form hydrogen bonds with water due to -COOH functional group
• as chain length increases, solubility decreases since CH2 groups do not form hydrogen bonds with water

Question 3

What are the melting points of carboxylic acids?

Answer 3

• can form hydrogen bonds between molecules with both the C=O and O-H parts of the functional group, their melting and bpts are even higher than those of alcohols, aldehydes and ketones

Question 4

How do carboxylic acids react with bases?

Answer 4

• weak acids react with bases in a neutralisation reaction to produce a salt

Question 5

What is the ester functional group?

Answer 5

• C double bond O and O bonded in chain

Question 6

How are esters named?

Answer 6

• formed from alcohol and carboxylic acids
• first part of name is from the alcohol and the second part is from the carboxylic acid

Question 7

How are esters formed?

Answer 7

• esterification reaction
• in presence of concentrated acid catalyst carried out under reflux
• conc H2SO4 often used
• condensation reaction

Question 8

Where does the molecule of water come from in esterification?

Answer 8

• -OH from acid and H from alcohol

Question 9

What are the properties of esters?

Answer 9

• sweet smelling compounds used in food flavouring and perfume
• low bpts
• good solvent for polar molecules

Question 10

How are acid anhydrides used?

Answer 10

• 2 molecules of a carboxylic acid are joined together (H2O removed)
• can be used to esterification alcohols
• don’t produce side products (apart from acid) so preferred reagent

Question 11

What are the products of the hydrolysis of esters under acidic conditions?

Answer 11

• carboxylic acid and alcohol
• simple reverse reaction

Question 12

What are the products of the hydrolysis of esters under alkaline conditions?

Answer 12

• carboxylate salt and an alcohol

Question 13

What is the functional group for acyl chlorides?

Answer 13

• COCl
• have the suffix -oyl chloride

Question 14

How are acyl chlorides produced?

Answer 14

• carboxylic acid + SOCl2 forms acyl chloride, SO2 and HCl

Question 15

What are the reactions of acyl chlorides?

Answer 15

• +water -> carboxylic acid
• +alcohol -> ester
• +ammonia -> amide
• +amines -> N-substituted amide
• acyl chlorides can also be used to esterify phenol which is not readily esterified by carboxylic acids