Introduction to Organic Chemistry

5 marks · Easy

Butanoic acid and butanol are both organic molecules with different functional groups.

(a)

State the functional group present in butanoic acid.

[1 mark]

(b)

What type of formula is shown by this representation: CH3CH2CH2COOH?

[1 mark]

(c)

Explain how the functional group in butanol affects its chemical properties.

[2 marks]

(d)

Give one similarity and one difference between the general formulae of carboxylic acids and alcohols.

[1 mark]

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

(a) Carboxyl group (–COOH)

(b) Condensed structural (structural) formula

(c) Butanol has the –OH functional group, making it an alcohol. This allows it to react with sodium, dissolve in water and be oxidised to acids.

(d) Similarity: Both general formulae contain the –OH group. Difference: Carboxylic acids contain an extra oxygen and have the –COOH group; their formula contains one more O than alcohols.

Common mistakes: Calling –COOH a carboxy rather than carboxyl group

Show mark scheme and worked solution

Marking points

B1 (a) · 1 mark · Correctly identifies –COOH as the carboxyl functional group.

B1 (b) · 1 mark · States 'condensed structural' or 'structural' formula.

B1 (c) · 2 marks · Explains effect of alcohol (–OH) group: 1 mark for identifying group, 1 mark for describing effect on chemical properties (e.g. reactions, solubility).

B1 (d) · 1 mark · States one similarity and one difference between the general formulae of carboxylic acids and alcohols, e.g. both have –OH, but acids have –COOH and one extra O.

Worked solution

a) The functional group in butanoic acid is the carboxyl group (–COOH).

b) The formula CH3CH2CH2COOH is a condensed structural (or structural) formula.

c) The –OH group in butanol makes it an alcohol, allowing it to react with sodium, dissolve in water, and be oxidised to a carboxylic acid.

d) Both types contain –OH in their formulae, but carboxylic acids have an extra O and the carboxyl group (–COOH), not just –OH.