Compound 'A' with molecular formula `C_(4)H_(9)`Br is treated with aq. KOH solution. The rate of this reaction depends upon the the concentration of the compounds 'A' only. When another optically active isomer 'B' of this compound was treated with aq. KOH solution, the rate of reaction was found to be dependent on concentration of compound and KOH both.
(i) Write down the structural formula of both compounds 'A' and 'B'.
(ii) Out of these two compounds, which one will be converted to the product with inverted configuration.

Explanation

(i). The available information suggests that the compound 'A' is a tertiary alkyl halide and its optically active isomer 'B' is a secondary alkyl halide.
(i). The structural formulae of the compound 'A' and 'B' are:
The compound 'A' being a tertiary alkyl halide will prefer to participate following `S_(N^(1))` mechanism. in this, the reaction rate depends on the concentration of alkyl halide only involved in the slow step and leading to a tertiary carbocation.
(ii). Compound 'B' is a secondary alkyl halide and has a chiral carbon. with aqueous KOH, It will react following `S_(N^(2))` mechanism leading to inversion of configuration.