Isomeric hydrocarbons $\quad \rightarrow \quad$ negative Baeyer's test (Molecular formula $\mathrm{C}_9 \mathrm{H}_{12}$ ) The total number of isomers from above with four different non-aliphatic substitution sites is -

Solution

$\begin{aligned} \text { Degree of unsaturation } & =\mathrm{C}+1-\frac{\mathrm{H}}{2} \\ & =9+1-6=4 \end{aligned}$ Benzene shows negative Baeyer's test
Both compounds have four different non-aliphatic substitution sites.

Hence, the correct answer is 2.