Question

In addition reactions of aldehydes, the carbonyl carbon atom changes from:

• A. $s{p}^3$ to $s{p}^2$
• B. $s{p}^2$ to $s{p}^3$
• C. sp to $s{p}^3$
• D. $s{p}^3$ to sp

Answer 1

The correct option is B $s{p}^2$ to $s{p}^3$

The carbonyl carbon atom has one $\pi$ bond, thus one empty p-orbital, therefore $s{p}^2$ hybridisation. On nucleophilic addition reaction $\pi$ bond is used up to form 4 $s{p}^3$ hybridised bonds. Thus hybridisation is changed from $s{p}^2$ to $s{p}^3$.