The reactions taking place with $$\mathrm{2- Phenyl-2-bromopropane}$$ as the starting material is shown below. Identify [A] and [B] formed in the reaction.

$$ \mathrm{C}_6 \mathrm{H}_5-\mathrm{C}\left(\mathrm{CH}_3\right)_2^{-} \mathrm{Br} \xrightarrow[\Delta]{\text { KOH Alcoholic }}[\mathrm{A}] $$

$$ [\mathrm{A}]+\mathrm{HBr} \xrightarrow{\left(\mathrm{C}_6 \mathrm{H}_5 \mathrm{CO})_2 \mathrm{O}\right.}[\mathrm{B}]$$

Which one of the following will undergo Nucleophilic substitution, by $$\mathrm{S}_{\mathrm{N}}{ }^1$$ mechanism, fastest?

Alkyl halides undergoing S_N2 reaction do inverse

The reaction $$\mathrm{ArN_2^ + C{l^ - }\buildrel {Cu/HCl} \over \longrightarrow ArCl + {N_2} + CuCl}$$ is called as