PL3 - Breaking Down Polymers

Question 1

What is the reverse process of esterification?

Answer 1

The hydrolysis of esters

Question 2

What molecule can be added to esters to break them down?

Answer 2

Water

Question 3

How do esters and water normally react?

What can be done to this process and why?

Answer 3

React very slowly so a catalyst usually added

Question 4

Which direction do catalysts added to esters work in (esterification/hydrolysis)?

Answer 4

The catalyst works both ways

Question 5

What type of catalyst is usually used for esterification/hydroysis?

Answer 5

A sulfuric acid catalyst

(Or any other acid)

Question 6

What is produces by the acid hydrolysis of an ester?

Answer 6

An alcohol and a carboxylic acid

Question 7

Why does an acid catalyst speed up the (acid) hydrolysis of an ester?

Answer 7

Excess water displaces the equilibrium position to the right and so the yield of products is improved

(Equation: Ester + Water ⇌ Alcohol + Carboxylic Acid)

Question 8

How would you make the hydrolysis of an ester go as far to completion as possible?

Answer 8

Add an excess of water or dilute acid (which also provides water)

Question 9

What type of reaction is the hydrolysis of esters?

Answer 9

Reversible

Question 10

What are the products of alkaline hydrolysis of esters?

Answer 10

An alcohol and a carboxylate salt

Question 11

Why is the alkaline hydrolysis of esters usually preffered?

Answer 11

Because the reaction goes to completion

Question 12

What causes the alkaline hydrolysis of an ester to form a carboxylate salt?

Answer 12

Nucleophilic substitution, caused by nucleophilic attack by the OH^-

Question 13

What type of reaction results in the breaking of amides?

Answer 13

Hydrolysis

Question 14

Which bond is hydrolysed in amides?

Answer 14

The C-N bond

Question 15

What are the conditions for the acid hydrolysis of an amide?

Answer 15

Amide is heated with moderately concentrated sulfuric/hydrochloric acid

Question 16

What are the products of the acid hydrolysis of a primary amide?

Answer 16

Primary amide + H₂O + H⁺ → (Carboxylic acid + Ammonia + H⁺) → Carboxylic Acid + Ammonium-anion salt

(Depending on acid used)

Question 17

What are the products of the acid hydrolysis of secondary amides?

Answer 17

Secondary amide + H₂O + H⁺ → Carboxylic acid + Amine salt

Corresponding anion for amine salt depending on acid:

E.g. CH₃NH₃⁺Cl^-

Question 18

What are the conditions for the alkaline hydrolysis of amides?

Answer 18

Heating with a moderately concentrated alkali

Question 19

What are the products of alkaline hydrolysis of a secondary amide?

Answer 19

Secondary amide + Alkali → Carboxylate Salt + Amine

(Salt dependant on cation from alkali)

Question 20

What are the products of the alkali hydrolysis of a primary amide?

Answer 20

Primary amide + Alkali → Carboxylate salt + Ammonia