1. Complete the following reactions:
a.

Explanation

a.
b. It is an example of Gattermann aldehyde reaction. The reaction is more favourable with activating groups.

c. It is an example of Vilsmeyer reaction.

2. i. `MeCHO + underset(("Weaker base"))(CN^(Θ)) hArr underset(("More basic than" CN^(Θ)))(MeCH(CN)O^(Θ))`
The equilibrium in the formation of weaker acid or waker base is favoured, so the equilibrium lies towards left. Consequently, reaction (ii) is more feasible for the formation of cyanohydrin.
`K_(eq.)` of `HCN gt K_(eq.) CN^(Θ)`
With strong base, cyanohydrin is converted to its conjugate base and then to the original aldehyde by the removal of `CN^(Θ)`.