The rate of $S_{N}2$ reaction is maximum when the solvent is

Dehydrohalogenation of $2$-bromobutane results in the formation of:

The following reaction is described as:
$CH_3(CH_2)_5-CH(CH_3)-Br + OH^- \rightarrow HO-CH(CH_3)(CH_2)_5CH_3 + Br^-$

The correct order of rates of $C-Br$ bond ionisation of the following bromides is

Which alkyl halide from the following pairs would you expect to react more rapidly by an $S_N2$ mechanism? Explain your answer.
$(i)$ $CH_3CH_2CH_2CH_2Br$ or $CH_3CH_2CH(Br)CH_3$
$(ii)$ $CH_3CH_2CH(Br)CH_3$ or $(CH_3)_3CBr$
$(iii)$ $CH_3CH(CH_3)CH_2CH_2Br$ or $CH_3CH_2CH(CH_3)CH_2Br$

$A$ compound $(a)$,$C_8H_9Br$,gives a white precipitate when heated with alcoholic $AgNO_3$. Oxidation of $(a)$ gives an acid $(b)$. The acid $(b)$,$C_8H_6O_4$,easily forms an anhydride on heating. Identify the compound $(a)$.