Question

Differentiate between the following:
(i) Propanal and Propanone,
(ii) Phenol and Benzoic acid.

Hint:

Remember that aldehydes and ketones are differentiated by the position of the carbonyl group, and phenol and benzoic acid are differentiated by the functional group attached to the benzene ring.

Answer 1

(i) Propanal and Propanone:
- Propanal (C\(_3\)H\(_6\)O): Propanal is an aldehyde with the structure CH\(_3\)CH\(_2\)CHO. The carbonyl group (\(C=O\)) is at the end of the carbon chain, making it an aldehyde. In this structure: - The carbonyl group is attached to a hydrogen atom and a CH\(_2\)-CH\(_3\) group. - The functional group in aldehydes is always a terminal carbonyl group, meaning the group is always attached to a carbon atom at the end of the molecule. - Propanone (C\(_3\)H\(_6\)O): Propanone is a ketone with the structure CH\(_3\)COCH\(_3\). The carbonyl group is attached to two methyl groups (CH\(_3\)), making it a ketone. - The carbonyl group is in the middle of the carbon chain, unlike in aldehydes. - In ketones, the carbonyl group is attached to two other carbon atoms, which makes it a characteristic feature of ketones. Key Difference: The key difference between propanal and propanone lies in the position of the carbonyl group: - In propanal, the carbonyl group is at the end of the molecule (making it an aldehyde). - In propanone, the carbonyl group is in the middle of the molecule (making it a ketone). (ii) Phenol and Benzoic acid:
- Phenol (C\(_6\)H\(_5\)OH): Phenol is an aromatic compound with a hydroxyl group (\(-OH\)) attached to a benzene ring. - The functional group in phenol is the hydroxyl group, which is directly attached to the aromatic ring. - Phenol has mild antiseptic properties and is used in the production of resins and other chemicals. - Benzoic acid (C\(_6\)H\(_5\)COOH): Benzoic acid is also an aromatic compound, but it contains a carboxyl group (\(-COOH\)) attached to the benzene ring. - The carboxyl group consists of a hydroxyl group (-OH) attached to a carbonyl group (\(C=O\)). - Benzoic acid is commonly used in the production of dyes, perfumes, and preservatives. Key Difference: The functional groups in these two compounds are different: - Phenol has a hydroxyl group (\(-OH\)) attached to the benzene ring. - Benzoic acid has a carboxyl group (\(-COOH\)) attached to the benzene ring. - This difference in functional groups leads to different chemical and physical properties for phenol and benzoic acid.