Possible isomers of $C_3H_6O$ that react with Grignard reagent

The molecular formula $C_3H_6O$ can correspond to:

• propanal: $CH_3CH_2CHO$
• propanone: $CH_3COCH_3$

Both aldehydes and ketones react with methylmagnesium bromide ($CH_3MgBr$).

Reaction of each with $CH_3MgBr$

(i) Propanal $CH_3CH_2CHO + CH_3MgBr \xrightarrow[]{ether} CH_3CH_2CH(CH_3)OMgBr \xrightarrow[]{H_3O^+} CH_3CH_2CH(OH)CH_3$ Product is butan-2-ol, a secondary alcohol.

Let this product be $C$ or $D$.

(ii) Propanone $CH_3COCH_3 + CH_3MgBr \xrightarrow[]{ether} (CH_3)_3COMgBr \xrightarrow[]{H_3O^+} (CH_3)_3COH$ Product is tert-butanol (2-methylpropan-2-ol), a tertiary alcohol.

Let this be the other product.

Chemical test distinction

So the two products formed must be:

• one secondary alcohol: butan-2-ol
• one tertiary alcohol: tert-butanol

These are distinguished by standard alcohol tests such as:

• oxidation test: secondary alcohol oxidizes, tertiary does not
• Lucas test: tertiary reacts immediately, secondary more slowly

Thus $C$ and $D$ respectively must correspond to

• $C =$ butan-2-ol
• $D =$ tert-butanol

matching the option that lists secondary alcohol first and tertiary alcohol second.

Comparison with stored answer

The stored correct answer is D, and this matches the derived result.