question_answer

Benzaldehyde is converted to benzyl alcohol by

A) Wurtz reaction

B) Cannizaro reaction

C) Fittig reaction

D) Wurtz-Fittig reaction

Correct Answer: B

Solution :

Key Idea: Write every reaction to find which of them is used to convert benzaldehyde to benzyl alcohol. (i) Wurtz reaction: In this reaction two molecules of alkyl halide react with sodium in presence of ether to form alkane having double the carbon atoms as present in alkyl halide. \[\underset{\begin{smallmatrix}  \text{alkyl}\, \\  \text{halide} \end{smallmatrix}}{\mathop{R-}}\,\underset{\begin{smallmatrix}  \text{alkyl} \\  \text{halide} \end{smallmatrix}}{\mathop{-R}}\,\xrightarrow{Ether}\] \[\underset{\text{alkane}}{\mathop{R-R}}\,+2NaX\] (ii) Fittig reaction: In this reaction two molecules of aryl halide react with sodium to form aromatic hydrocarbon. (iii) Wurtz-Fittig reaction: In this reaction one molecule of aryl halide and one molecule of alkyl halide react with sodium to form alkyl substituted benzene. (iv) Cannizaro reaction: This reaction is given by aldehydes which do not have \[\alpha -\]hydrogen atoms. This is disproportionation reaction in which half of the molecules are oxidised and other half are reduced. \[\therefore \] Cannizaro reaction is used for conversion of benzaldehyde into benzyl alcohol.