Question

Benzene nitrile on reaction with reagent (A) gave product (X). In another reaction with reagent (B) gave product (Y). \(X\) and \(Y\) both form oxime but only \(Y\) gets oxidized with ammoniacal silver nitrate solution. The correct reagents \(A\) and \(B\) respectively are \[ \begin{aligned} \text{I. }&\mathrm{CH_3CH_2MgBr,\ H_2O} \qquad;\qquad \mathrm{DIBAL\!-\!H,\ H_2O} \text{II. }&(\mathrm{CH_3CH_2})_2\mathrm{Cd} \qquad;\qquad \mathrm{SnCl_2+HCl,\ H_2O} \text{III. }&\mathrm{CH_3CH_2MgBr,\ H_2O} \qquad;\qquad \mathrm{SnCl_2+HCl,\ H_2O} \text{IV. }&(\mathrm{CH_3CH_2})_2\mathrm{Cd} \qquad;\qquad \mathrm{DIBAL\!-\!H,\ H_2O} \end{aligned} \] The correct answer is

• A. III, IV
• B. I, II
• C. I, III
• D. II, IV

Hint:

Important reactions of nitriles: \[ \boxed{ \begin{aligned} \mathrm{RCN} &\xrightarrow{\mathrm{RMgX}} \text{Ketone} \mathrm{RCN} &\xrightarrow{\mathrm{DIBAL\!-\!H}} \text{Aldehyde} \mathrm{RCN} &\xrightarrow{\mathrm{SnCl_2/HCl}} \text{Aldehyde (Stephen reaction)} \end{aligned} } \]

Answer 1

The Correct Option is C

Step 1: Identify product \(X\). Reaction of benzonitrile with \[ \boxed{\mathrm{CH_3CH_2MgBr}} \] followed by hydrolysis gives a ketone. \[ \mathrm{C_6H_5CN} \rightarrow \boxed{\mathrm{C_6H_5COC_2H_5}} \] Ketones form oximes but do not reduce Tollens' reagent.

Step 2: Identify product \(Y\). Both \[ \boxed{\mathrm{DIBAL\!-\!H}} \] and \[ \boxed{\mathrm{SnCl_2/HCl}} \] (Stephen reduction) convert benzonitrile into benzaldehyde. \[ \mathrm{C_6H_5CN} \rightarrow \boxed{\mathrm{C_6H_5CHO}} \] Benzaldehyde forms oxime and gives a positive Tollens' test. Hence, \[ \boxed{\text{Sets I and III are correct}.} \] Therefore, \[ \boxed{(C)} \] is the correct answer.