Identify $\mathrm{Z}$ in the following reaction sequence:

${\mathrm{CH}}_3\mathrm{CHO}\underset{\mathrm{Dilute} {\mathrm{H}}_2{\mathrm{SO}}_4}{\overset{{\mathrm{MnO}}_4^{-}}{\to }}\mathrm{X}\stackrel{{\mathrm{SOCl}}_2}{\to }\mathrm{Y}\underset{∆}{\overset{{\mathrm{CH}}_3\mathrm{COONa}}{\to }}\mathrm{Z}$

A cyclic compound that gives succinic acid on oxidative cleavage is-

Which of the following acids will undergo decarboxylation easily?

${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}\stackrel{{\mathrm{PCl}}_5}{⟶}\mathrm{A}+{\mathrm{POCl}}_3+\mathrm{HCl}$ . Compound $\mathrm{A}$ can also be formed by treating chlorine with the following compound in the absence of a halogen carrier-

Which of the following decolourises the colour of acidic ${\mathrm{KMnO}}_4$?

In the Cannizzaro reaction given below,

 $2\mathrm{PhCHO} \stackrel{\stackrel{\mathrm{\Theta }}{\mathrm{O}}\mathrm{H}}{\to }{\mathrm{PhCH}}_2\mathrm{OH}+{\mathrm{PhCO}}_2^{\Theta }$, the slowest step is :