Organic Chemistry

Acetone ($\text{CH}_3\text{COCH}_3$) contains a methyl ketone group ($\text{CH}_3\text{C}=\text{O}$), so it reacts with iodine and sodium hydroxide ($\text{I}_2/\text{NaOH}$) to give a yellow precipitate of iodoform ($\text{CHI}_3$). Benzophenone ($\text{C}_6\text{H}_5\text{COC}_6\text{H}_5$) lacks a methyl ketone group and does not give this test. Both give negative Tollens' and Fehling's tests and positive 2,4-DNP tests.

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.