See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Concept: The equilibrium constant for hydration of a carbonyl compound (formation of gem-diol) depends on how electrophilic the carbonyl carbon is and how much steric hindrance is present around it. More electrophilic (electron-poor) carbonyl carbon and less steric bulk both favor hydration, giving a larger equilibrium constant. Step 1 - Identify structural features affecting hydration: - (A) Acetone: Two electron-donating methyl groups attached to carbonyl; significant steric hindrance. Least reactive toward nucleophilic addition. - (B) Acetaldehyde (CH3CHO): One methyl group (electron-donating) and one H; less steric hindrance than acetone. - (C) Chloroacetone (CH3COCH2Cl): One methyl (electron-donating) and one -CH2Cl (weakly electron-withdrawing via induction, but remote); slightly more electrophilic than acetone but ketone still has two carbon substituents. - (D) Formaldehyde (HCHO): Two H atoms; no electron-donating alkyl groups; least steric hindrance; most electrophilic carbonyl. Highest Keq. - (E) Chloroacetaldehyde (ClCH2CHO): One H and one -CH2Cl; the electron-withdrawing Cl increases electrophilicity of carbonyl compared to acetaldehyde; more reactive than acetaldehyde but less than formaldehyde. Step 2 - Rank by increasing Keq: - A (ketone, two methyl groups, most hindered/least electrophilic) < C (ketone but one CH2Cl group, slightly better than A) < B (aldehyde, one methyl) < E (aldehyde, one CH2Cl - more electrophilic than acetaldehyde) < D (formaldehyde, most electrophilic, least hindered) This gives the order: A < C < B < E < D Step 3 - Match to options: This matches option (b): A < C < B < E < D. Why other options fail: - (a) A < B < C < D < E ignores that chloroacetone (C) is more reactive than acetone but less than acetaldehyde, and places E after D incorrectly. - (c) A < C < E < B < D would mean chloroacetaldehyde is less reactive than acetaldehyde, which is incorrect since Cl is electron-withdrawing. - (d) C < A < B < E < D places chloroacetone below acetone, which is incorrect. Therefore, the correct answer is B.