MR - Amines, Amides and Hydrolysis

Question 1

Describe the structure of a:

i) primary amine
ii) secondary amine
iii) tertiary amine

Answer 1

i) Nitrogen bonded to an R group and 2 Hydrogen atoms
ii) Nitrogen bonded to 2 R groups and a Hydrogen atom
iii) Nitrogen bonded to 3 R groups

Question 2

What Prefix/Suffix is given to:

i) amine groups
ii) amide groups

Answer 2

i) Amino-

ii) -amide

Question 3

Explain why an amine is a base

Answer 3

It has a lone pair of electrons so can accept protons and form dative covalent bonds with an H⁺ ion

Question 4

What is formed when an amine is reacted with an acid?

Answer 4

An ammonium salt

Question 5

State what group amides have and give the functional group for amides

Answer 5

Amides contain carbonyl groups

-CONH₂

Question 6

Why do amides behave differently to amine groups

Answer 6

The carbonyl group pulls electrons away from the rest of the amide group

Question 7

What is formed when amines are acylated?

Answer 7

N-substituted amides

Question 8

Give the products for the reaction between ethanoyl chloride and aminomethane

Answer 8

N-methylethanamide and HCl

Question 9

Give the products for hydrolysing an amide with:

i) dilute acid
ii) dilute alkali

Answer 9

i) A carboxylic acid and an ammonium salt

ii) A carboxylate ion and ammonia gas

Question 10

Give the products for the acid hydrolysis of esters

Answer 10

A carboxylic acid and an alcohol

Question 11

Explain why large volumes of water may be needed to hydrolyse an ester

Answer 11

Because the hydrolysis of esters is a reversible reaction, so large volumes of water are needed to push the equilibrium towards the products

Question 12

State the function of the H⁺ ions in the acid hydrolysis of esters

Answer 12

To act as a catalyst

Question 13

Give the products for the base hydrolysis of esters

Answer 13

A carboxylic acid salt and an alcohol

Question 14

State a method to purify organic solutions

Answer 14

Recrystallisation

Question 15

Define saturated solution

Answer 15

A saturated solution is where the maximum possible amount of solid is dissolved in the solution

Question 16

Describe how recrystallisation is carried out

Answer 16

1) A very hot solvent is added to the impure solid until it just dissolves
2) This gives a saturated solution of the impure product
3) The solution is left to cool down slowly. Crystals of the products form as it cools
4) Impurities stay in the solution. They’re present in much smaller amounts than the product, so they’d take much longer to crystallise out
5) The crystals are removed by filtration and washed with ice-cold solvent. They are then dried - leaving you with crystals of your product that are much purer than the original solid

Question 17

When choosing a solvent for recrystallisation, under what conditions do you want the solubility of the product to be highest and lowest?

Answer 17

Very soluble in hot solvent

Nearly insoluble in cold solvent

Question 18

For recrystallisation, explain what will happen if your product isn’t soluble enough in the hot chosen solvent

Answer 18

You will not be able to dissolve it at all

Question 19

For recrystallisation, explain what will happen if your product is too soluble in the cold chosen solvent

Answer 19

Most of the product will stay in the solution, even after cooling. When you filter it, you’ll lose most of your product, giving a very low yield