Question

Would you expect the carbonyl carbon of benzaldehyde to be more or less electrophilic than that of acetaldehyde? Explain using resonance structures.

Answer 1

Answer:

Benzaldehyde is less electrophilic than acetaldehyde

Explanation:

Electrophilicity of carbonyl carbon depends on it's positive charge density.

In benzaldehyde, phenyl group can act as an electron donating group towards carbonyl group due to it's electron donating resonating effect.

In acetaldehyde, methyl group can act as an electron donating group towards carbonyl group due to it's electron donating inductive effect.

We know that resonating effect are more stronger than inductive effect.

Henece, it is expected that positive charge density on carbonyl carbon is much lower in benzaldehyde than acetaldehyde.

So, benzaldehyde is less electrophilic than acetaldehyde.

Resonating effect of phenyl group has been shown below.