Edexcel A-Level Chemistry A2 18.5 The Mechanism of the Electrophilic Substitution Reactions of Benzene in Halogenation Nitration and Friedel Crafts Reactions Questions

Ignore omission or incorrect placement of methyl groups in M2 and M3

$\mathrm{HNO}_{3}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{NO}_{2}{ }^{+}+\mathrm{HSO}_{4}{ }^{-}+\mathrm{H}_{2} \mathrm{O}$

OR

$\mathrm{HNO}_{3}+2 \mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{NO}_{2}{ }^{+}+2 \mathrm{HSO}_{4}{ }^{-}+\mathrm{H}_{3} \mathrm{O}^{+}$

OR

$\mathrm{HNO}_{3}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{H}_{2} \mathrm{NO}_{3}{ }^{+}+\mathrm{HSO}_{4}{ }^{-}$and $\mathrm{H}_{2} \mathrm{NO}_{3}{ }^{+} \rightarrow \mathrm{NO}_{2}{ }^{+}+\mathrm{H}_{2} \mathrm{O}$

(4)

Expert

TE on electrophile from M1 provided positively charged

Do not award lone pair on N of $\mathrm{NO}_{2}{ }^{+}$

An answer that makes reference to the following points:

- equation for formation of nitronium ion

(1)

- curly arrow from within hexagon to

(1) anywhere on $\mathrm{NO}_{2}{ }^{+}$

- structure of intermediate ion

(1)

- curly arrow from C-H bond to within ring and

correct product

and

$\mathrm{H}^{+}$

(1)