Among the following, the number of ortho para directing with activating group.

(1) $-{\mathrm{NH}}_2$

(2) $-\mathrm{OH}$

(3) $-\mathrm{OMe}$

(4) $-\mathrm{Cl}$

(5) $-\mathrm{O}-\stackrel{\underset{\parallel }{\mathrm{O}}}{\mathrm{C}}-{\mathrm{CH}}_3$

(6) $-\mathrm{NH}-\stackrel{\underset{\parallel }{\mathrm{O}}}{\mathrm{C}}-{\mathrm{CH}}_3$

(7) $-{\mathrm{CCl}}_3$

(8) $-{\mathrm{CF}}_3$

(9) $-\mathrm{CH}=\mathrm{CH}-\mathrm{COOH}$

(10) $-{\mathrm{NO}}_2$

(11) $-\mathrm{COOH}$

Among the following the number of reagents can be used to generate $\stackrel{\oplus }{\mathrm{N}}{\mathrm{O}}_2$ in nitration of benzene rings..

(1) conc. ${\mathrm{HNO}}_3+$conc. ${\mathrm{H}}_2{\mathrm{SO}}_4$

(2) ${\mathrm{HNO}}_3+{\mathrm{HClO}}_4$

(3) Solid ${\mathrm{N}}_2{\mathrm{O}}_5$

(4) conc. ${\mathrm{HNO}}_3+$conc.${\mathrm{HNO}}_2$

(5) conc.${\mathrm{H}}_2{\mathrm{SO}}_4$

(6) ${\mathrm{NaNO}}_2+\mathrm{HCl}$

Number of compounds that gives a tribromo derivative on treatment with bromine water.

Electrophilic attack of $\stackrel{\oplus }{\mathrm{N}}{\mathrm{O}}_2$ at meta position is observed in

The nitration will mainly take place at the position:

How many $\mathrm{\pi }$ electrons are there in the following species?

The most stable intermediatry carbocation and major product in following reactions:

Give mechanism of this reaction.