Q. Benzaldehyde is converted to benzyl alcohol by
VMMC MedicalVMMC Medical 2007
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.
