Answer 1

1. This reaction is given only by aldehydes having no α-hydrogen atom.
2. Aldehydes undergo self -oxidation and reduction reaction on heating with concentrated alkali.
3. In Cannizzaro reaction, one molecule of an aldehyde is reduced to alcohol and at the same time the second molecule is oxidized to carboxylic acid salt. Thus, the reaction is an example of disproportionation reaction.

e.g. 1. \[\begin{array}{cc}
\ce{O\phantom{.................................}}\ce{O\phantom{..................}}\ce{H\phantom{}}\\
||\phantom{.................................}||\phantom{...................}|\\
\ce{\underset{\text{Formaldehyde}}{2H - C - H} + \underset{\text{Sodium hydroxide (50%)}}{NaOH} ->[\triangle] \underset{\text{Sodium formate}}{H - C - O- Na+} + H - C - OH}\\\phantom{......................................................}|\\\ce{\phantom{......................................................}\underset{\text{Methanol}}{H}}\end{array}\]

2.