Unit 3-Ethers, Carboxylic Acids And Amines

Question 1

What general structure is present in ethers?

Answer 1

R’ – O – R’’, where R’ and R’’ are alkyl groups.

Question 2

How are ethers named?

Answer 2

named as substituted alkanes.

The alkoxy group is named by adding the ending ‘oxy’ to the alkyl substituent, and this prefixes the name of the longest carbon chain

Question 3

How are ethers prepared

Answer 3

nucleophilic substitution reaction between monohaloalkane and an alkoxide.

Question 4

Explain the difference in boiling points between an ether and the corresponding isomeric alcohol.

Answer 4

Due to the lack of hydrogen bonding between ether molecules, they have lower boiling points than the corresponding isomeric alcohols.

Question 5

What happens to the solubility of ethers are molecular size increases?

Answer 5

Solubility decreases

Question 6

Give a use of an ether.

Answer 6

Solvents

Question 7

Preparation of carboxylic acids

Answer 7

• oxidising primary alcohols using acidified permanganate, acidified dichromate and hot copper(II) oxide
• oxidising aldehydes using acidified permanganate, acidified dichromate, Fehling’s solution and Tollens’ reagent
• hydrolysing nitriles, esters or amides

Question 8

Reactions of carboxylic acids include:

Answer 8

• formation of salts by reactions with metals or bases
• condensation reactions with alcohols to form esters in the presence of concentrated sulfuric or concentrated phosphoric acid
• reaction with amines to form alkylammonium salts that form amides when heated
• reduction with lithium aluminium hydride to form primary alcohols

Question 9

Explain the difference between primary, secondary, and tertiary amines.

Answer 9

classified according to the number of alkyl groups attached to the nitrogen atom.

Question 10

What type of reaction happens when an amine reacts with an acid?

Answer 10

Neutralisation

Question 11

Primary and secondary amines have higher boiling points than isomeric tertiary amines.

Explain

Answer 11

Primary and secondary amines, but not tertiary amines, display hydrogen bonding.

Question 12

Why are shorter chain length amines soluble in water?

Answer 12

They can hydrogen bond with water molecules.

Question 13

Are amines like ammonia weak acids or bases?

Answer 13

weak bases and dissociate to a slight extent in aqueous solution. The nitrogen atom has a lone pair of electrons which can accept a proton from water, producing hydroxide ions