Question

Write the chemical equation for the preparation of anisole. Write the chemical equations of its reactions with:
i) Acetyl chloride
ii) Hydrogen iodide
iii) Mixture of conc.\ H$_2$SO$_4$ and conc.\ HNO$_3$

Hint:

The $-OCH_3$ group is a strong ortho/para director, so electrophilic substitutions (acylation, nitration) give mainly para products; with HI, anisole cleaves at the alkyl–oxygen bond to yield phenol and methyl iodide.

Answer 1

Preparation of anisole (Williamson ether synthesis):
First form sodium phenoxide, then methylate.
\[ \mathrm{C_6H_5OH} + \mathrm{NaOH} \rightarrow \mathrm{C_6H_5ONa} + \mathrm{H_2O} \]
\[ \mathrm{C_6H_5ONa} + \mathrm{CH_3I} \rightarrow \mathrm{C_6H_5OCH_3}\ (\text{anisole}) + \mathrm{NaI} \]
i) With acetyl chloride (Friedel–Crafts acylation):
\[ \mathrm{C_6H_5OCH_3} + \mathrm{CH_3COCl} \xrightarrow[\text{anhyd.}]{\mathrm{AlCl_3}} \ p\text{-}\mathrm{CH_3CO\!-\!C_6H_4OCH_3}\ +\ \text{minor } o\text{-isomer} + \mathrm{HCl} \]
(para-methoxyacetophenone major, ortho minor).
ii) With hydrogen iodide (ether cleavage):
\[ \mathrm{C_6H_5OCH_3} + \mathrm{HI} \xrightarrow{\Delta} \ \mathrm{C_6H_5OH} + \mathrm{CH_3I} \]
iii) With conc.\ H$_2$SO$_4$/conc.\ HNO$_3$ (nitration):
\[ \mathrm{C_6H_5OCH_3} \xrightarrow[\text{conc.\ } \mathrm{H_2SO_4}]{\text{conc.\ } \mathrm{HNO_3}} \ p\text{-}\mathrm{NO_2\!-\!C_6H_4OCH_3}\ +\ \text{minor } o\text{-isomer} + \mathrm{H_2O} \]