Read the passage carefully and answer the Questions.
Aldehydes and ketones are important organic compounds prepared mainly by oxidation of alcohols. Primary alcohols give aldehyde and secondary alcohols yield ketones. Aldehydes can also be formed by partial reduction of acid chlorides, reduction of esters or by Gattermann-Koch reaction. Ketones are prepared via Friedel-Craft's acylation, hydration of alkyne and reaction of Grignard's reagent with nitriles. Chemically, aldehydes and ketones are reactive in nature due to the carbonyl group and undergo nucleophilic addition reactions. Aldehydes are more reactive than ketones and can be oxidized to carboxylic acids, while both can be reduced to alcohols or hydrocarbons and exhibit condensation reaction.
The correct structure of the product in the following reaction is;
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 1-phenylpropan-1-one (ethyl phenyl ketone)
The carbon atom of the \( \ce{C#N} \) group is electrophilic. In a Grignard reagent the carbon bonded to magnesium carries a partial negative charge, so it acts as a nucleophile and adds to the nitrile carbon, giving the magnesium salt of an imine. Acid hydrolysis of the imine replaces the =N– part by =O, so a nitrile and a Grignard reagent together give a ketone.
Here the phenyl group of \( \ce{C6H5MgBr} \) adds to the nitrile carbon of propanenitrile (ethyl cyanide), in dry ether:
\( \displaystyle \ce{C2H5-C#N + C6H5MgBr} \xrightarrow{\text{dry ether}} \ce{C2H5-C(=NMgBr)-C6H5} \)
Hydrolysis with dilute acid then gives the ketone:
\( \displaystyle \ce{C2H5-C(=NMgBr)-C6H5 + 2H2O} \xrightarrow{\ce{H3O+}} \ce{C2H5-CO-C6H5 + NH3 + Mg(OH)Br} \)
The carbonyl carbon is the old nitrile carbon, now bonded to the ethyl group and to the phenyl group. So A is \( \ce{C6H5COCH2CH3} \), 1-phenylpropan-1-one (propiophenone), the structure in Option (1).
Why the other options are incorrect
Option (2) 1-phenylpropan-2-one — Incorrect. Here the carbonyl carbon is bonded to a methyl group and a benzyl group (\( \ce{C6H5CH2-} \)); the product of this reaction has the phenyl ring directly on the carbonyl carbon.
Option (3) 3-phenylpropanal — Incorrect. This is an aldehyde with the ring at the far end of the chain. A nitrile gives an aldehyde only on reduction (Stephen reaction, \( \ce{SnCl2}/\ce{HCl} \)), not with a Grignard reagent.
Option (4) 1-phenylpropan-1-ol — Incorrect. This secondary alcohol is formed when \( \ce{C6H5MgBr} \) adds to an aldehyde (propanal); hydrolysis of the imine salt from a nitrile stops at the ketone.
NCERT (2026-27 edition):
From Nitriles
