कार्बनिक रसायन

Reactivity towards nucleophilic attack on carbonyl carbon depends on steric and electronic factors:

• Ketones are less reactive than aldehydes due to greater steric hindrance and electron donation from the methyl group. Hence, Acetophenone is the least reactive.
• Among aromatic aldehydes, electron-donating groups ($-\text{CH}_3$) reduce electrophilicity: p-Tolualdehyde < Benzaldehyde.
• Strong electron-withdrawing groups ($-M/-I$ of $-\text{NO}_2$) strongly increase the positive charge on carbonyl carbon, making p-Nitrobenzaldehyde the most reactive.
  
  Increasing order: Acetophenone < p-Tolualdehyde < Benzaldehyde < p-Nitrobenzaldehyde.

In the Gatterman-Koch reaction, benzene reacts with $\text{CO}$ and $\text{HCl}$ in the presence of anhydrous $\text{AlCl}_3$ and $\text{CuCl}$:

The formyl cation ($\text{HCO}^+$) acts as the active electrophile that attacks the aromatic ring to produce benzaldehyde.

Cannizzaro reaction occurs specifically in aldehydes that do not have any $\alpha$-hydrogen atom (Statement B is correct).
When heated with concentrated alkali (e.g. $50\%\text{ NaOH}$), one molecule is reduced to methanol while another is oxidised to sodium formate (disproportionation / self-oxidation-reduction reaction; Statement D is correct):