Ethyl isocyanide on hydrolysis in acidic medium generates:

In the following sequence of reactions:   

Toluene $\stackrel{{\mathrm{KMnO}}_4}{\to }\mathrm{A}\stackrel{{\mathrm{SOCl}}_2}{\to }\mathrm{B}\underset{{\mathrm{BaSO}}_4}{\overset{{\mathrm{H}}_2/\mathrm{Pd}}{\to }}\mathrm{C}$ the product $\mathrm{C}$ is:

Phenol on treatment with ${\mathrm{CO}}_2$ in the presence of $\mathrm{NaOH}$ followed by acidification produces compound $\mathrm{X}$ as the major product. $\mathrm{X}$ on treatment with ${\left({\mathrm{CH}}_3\mathrm{CO}\right)}_2\mathrm{O}$ in the presence of catalytic amount of ${\mathrm{H}}_2{\mathrm{SO}}_4$ produces: 

The general formula ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}}{\mathrm{O}}_{\mathrm{2}}$ could be for open chain _______.