Scottish Highers Chemistry Fats and Oils: 7. Esters can be synthetic or na

Question

7. Esters can be synthetic or natural.

(a) The synthetic polyester PET, poly(ethylene terephthalate), has many ester links. PET can break down by a free radical reaction. One of the steps involved in breaking down PET is shown below:

H   H   O   H   H   H   H   H
|   |   ||  |   |       |   |
H---C---C---O---C---C---C---C---H
|   |   |   |   |       |   |
H   H   O   H   H   H   H   H

(i) State the name for this step.

(ii) Name the component of sunlight that can cause plastics such as PET to break down.

(iii) Name the type of substance that can be added to plastics to prevent them breaking down in this way.

(b) Natural cyclic esters called lactones can be formed from hydroxycarboxylic acids.

5-hydroxypentanoic acid is a hydroxycarboxylic acid that when heated, with dilute acid, will form a cyclic ester.

Name product Y in this reaction.

(ii) Draw the structure for the cyclic compound formed when 4-hydroxypentanoic acid is heated with dilute acid.

H   H   O   H
|   |   ||
H---C---C---C---C---H
|   |   |   |  
H   H   H   H

4-hydroxypentanoic acid

(iii) Name the hydroxycarboxylic acid shown below:

H   H      O
|   |      ||
H---C---C---C---C---OH
|   |      |   |      |
H   H      H   H      OH

7. Esters can be synthetic or natural - Scottish Highers Chemistry - Question 7 - 2019

Worked Solution & Example Answer:7. Esters can be synthetic or natural - Scottish Highers Chemistry - Question 7 - 2019

(i) State the name for this step.

(ii) Name the component of sunlight that can cause plastics such as PET to break down.

(iii) Name the type of substance that can be added to plastics to prevent them breaking down in this way.

(i) Name product Y in this reaction.

(ii) Draw the structure for the cyclic compound formed when 4-hydroxypentanoic acid is heated with dilute acid.

(iii) Name the hydroxycarboxylic acid shown below.

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