question_answer

Ketones can be prepared by

A)  Rosenmund reduction

B)  Etard reaction

C)  Cannizaro reaction

D)  Friedel-Craft reaction

Correct Answer: D

Solution :

(i) By Rosenmund reduction aldehydes are formed. \[\underset{acid\,\,chloride}{\mathop{R-\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-Cl}}\,+{{H}_{2}}\xrightarrow[Boiling\,\,xylene]{Pd,\,\,BaS{{O}_{4}},\,\,S}\]                                                 \[\underset{aldehyde}{\mathop{R-\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-H+HCl}}\,\] (ii) By Etard reaction, benzaldehyde is formed.                                                 (iii) By cannizaro reaction, alcohols and salts of carboxylic acids are formed. \[\underset{formaldehyde}{\mathop{2H-\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-H}}\,\xrightarrow{NaOH(aq)}\underset{methyl\,\,alcohol}{\mathop{C{{H}_{3}}-OH}}\,\]                                                 \[\underset{sod.\,\,formate}{\mathop{H-\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-ONa}}\,\] (iv) By Friedel-Crafts acyladon, aromatic ketones are formed.