Question

Draw the structure of 'X' in the following reaction:
(a primary alcohol / suitable substrate) + CrO₃ → 'X'

Hint:

CrO 3 (chromium trioxide, an oxidising agent) oxidises an alcohol to a carbonyl compound.

Answer 1

Step 1: Role of the reagent.
\(CrO_3\) (chromium trioxide) is an oxidising agent that converts alcohols into carbonyl compounds.

Step 2: Effect on a primary alcohol.
A primary alcohol \(R-CH_2-OH\) is first oxidised to an aldehyde \(R-CHO\). With excess strong oxidant in acidic medium it can go further to a carboxylic acid \(R-COOH\).

Step 3: Effect on a secondary alcohol.
A secondary alcohol \(R_2CH-OH\) is oxidised to a ketone \(R_2C=O\).

Step 4: Identify X.
For a primary alcohol substrate, the immediate product X is the corresponding aldehyde \(R-CHO\). For example ethanol gives ethanal, \(CH_3CHO\).

Step 5: Note.
The product X is the carbonyl compound; its exact structure depends on the alcohol given, but the key point is the C=O group is formed.

Answer: X is the carbonyl compound, an aldehyde \(R-CHO\) from a primary alcohol (for example \(CH_3CHO\) from ethanol) or a ketone from a secondary alcohol.