Two isomers $(A)$ and $(B)$ with Molar mass $184 \mathrm{~g} / \mathrm{mol}$ and elemental composition $C, 52.2 \% ; H, 4.9 \%$ and $B r 42.9 \%$ gave benzoic acid and pbromobenzoic acid, respectively on oxidation with $\mathrm{KMnO}_4$. Isomer ' A ' is optically active and gives a pale yellow precipitate when warmed with alcoholic $\mathrm{AgNO}_3$. Isomer 'A' and 'B' are, respectively :