Question

Write chemical equations of the reactions of five methods of preparation of aldehyde.

Hint:

Aldehydes can be prepared from alcohols, acid chlorides, nitriles, and hydrocarbons.

Answer 1

(i) Oxidation of primary alcohol: \[ RCH_2OH + [O] \rightarrow RCHO + H_2O. \] (ii) Rosenmund reduction: \[ RCOCl + H_2 \xrightarrow{Pd/BaSO_4} RCHO. \] (iii) Stephen reaction: \[ R-CN + 2[H] \xrightarrow{SnCl_2/HCl} RCHO. \] (iv) Hydrolysis of geminal dihalides: \[ RCHCl_2 + H_2O \rightarrow RCHO + 2HCl. \] (v) Gattermann-Koch reaction: \[ C_6H_6 + CO + HCl \xrightarrow{AlCl_3} C_6H_5CHO. \]