(I) For the Cannizzaro reaction, the compound must be non-enolizable aldehyde (without alpha-hydrogens). In this case, the compound undergoes disproportionation in the presence of a strong base, forming one alcohol and one carboxylic acid.
(II) A compound that reduces Tollens' reagent is an aldehyde. If it has a chiral carbon, it is asymmetric and can show optical activity.
(III) The positive iodoform test indicates the presence of a methyl ketone group (-COCH$_3$) or a structure that can undergo oxidation to form such a group.
(ii) Write the reaction involved in the following:
(I) Clemenssen reduction.
(II) Etard reaction.
(I) Clemenssen reduction involves the reduction of carbonyl compounds to hydrocarbons using zinc amalgam (Zn/Hg) and hydrochloric acid (HCl).
\[ \text{Aldehyde or Ketone} + \text{Zn/Hg} \longrightarrow \text{Alkane} \]
(II) Etard reaction involves the oxidation of methyl groups attached to aromatic rings to an aldehyde in the presence of chromium-based reagents.
\[ \text{Toluene} + \text{CrO}_2\text{Cl}_2 \longrightarrow \text{Benzaldehyde} \]