Chemistry 2005 JAMB Past Questions - Question 14: Which of the following are structural isomers?

Correct Answer

B

Explanation

Structural isomers are molecules that have the same molecular formula but different structural arrangements of atoms. Let's analyze the given pairs:

1. Propanoic acid and propan-1,2-diol:
  - Propanoic acid: CH₃CH₂COOH
  - Propan-1,2-diol: CH₃CHOHCH₂OH

  These molecules have different structures and are structural isomers.

2. Propanal and propanone:
  - Propanal: CH₃CH₂CHO
  - Propanone (acetone): (CH₃)₂CO

  These molecules have different structures and are structural isomers.

3. Ethanoic acid and propanoic acid:
  - Ethanoic acid (acetic acid): CH₃COOH
  - Propanoic acid: CH₃CH₂COOH

  These molecules have different structures and are not structural isomers.

4. Ethan-1,2-diol and ethanoic acid:
  - Ethan-1,2-diol (ethylene glycol): HOCH₂CH₂OH
  - Ethanoic acid (acetic acid): CH₃COOH

  These molecules have different structures and are not structural isomers.

So, the pairs that are structural isomers are:
- Propanoic acid and propan-1,2-diol
- Propanal and propanone