Question

Draw the structure of 'X' in the following reaction: a compound is treated with CrO₃ to give 'X'.

Hint:

CrO 3 (chromium trioxide, often in acidic conditions) is a strong oxidising agent.

Answer 1

Step 1: Identify the reagent.
\(CrO_3\) (chromium trioxide) is a strong oxidising agent, usually used in an acidic medium.

Step 2: Recall what it does to alcohols.
A primary alcohol is oxidised to a carboxylic acid, a secondary alcohol to a ketone, and a tertiary alcohol resists oxidation.

Step 3: Apply to the given case.
For the standard textbook case, a secondary alcohol on treatment with \(CrO_3\) gives a ketone, and a primary alcohol gives the carboxylic acid.

Step 4: Pick the product X.
Taking the common example of a primary alcohol such as ethanol, \(CrO_3\) oxidises it to the carboxylic acid (ethanoic acid). For a secondary alcohol such as propan-2-ol, the product X is propan-2-one.

Step 5: Write the conversion.
\[R-CH_2-OH \xrightarrow{CrO_3} R-COOH \quad ; \quad R_2CH-OH \xrightarrow{CrO_3} R_2C{=}O\]

Answer: X is the oxidation product: a primary alcohol gives a carboxylic acid (\(R-COOH\)) and a secondary alcohol gives a ketone (\(R_2C{=}O\)) on treatment with \(CrO_3\).