See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Concept: Acid chlorides (acyl chlorides) are highly reactive acylating agents. When an acyl chloride reacts with a nucleophile, the nucleophile attacks the electrophilic carbonyl carbon and the chloride leaves as the leaving group (nucleophilic acyl substitution). Step 1: Identify the reactants. Acetyl chloride (CH3-C(=O)-Cl) reacts with hydrogen sulfide (H2S). Step 2: Identify the nucleophile. H2S acts as a nucleophile through its sulfur atom (analogous to how H2O acts as a nucleophile). The sulfur in H2S attacks the electrophilic carbonyl carbon of acetyl chloride. Step 3: Mechanism. The sulfur of H2S attacks the carbonyl carbon of CH3COCl, forming a tetrahedral intermediate. The chloride ion then departs as the leaving group. This generates CH3-C(=O)-SH (thioacetic acid), with HCl as a byproduct. Step 4: Evaluate options. - Option (a): Involves addition rather than substitution and breaks aromaticity of the carbonyl; not the product of nucleophilic acyl substitution. - Option (b): CH3-C(=O)-SH is the direct product of nucleophilic acyl substitution where -Cl is replaced by -SH. This is correct. - Option (c): CH3-C(=S)-Cl would require replacement of the oxygen, not chlorine; H2S is not an oxidant and does not exchange O for S under these conditions. - Option (d): The anhydride-type product would require two equivalents of acyl chloride reacting with one sulfide dianion; this is not the major product under simple H2S conditions. Step 5: Conclusion. The nucleophilic acyl substitution of H2S with acetyl chloride replaces Cl with SH, giving thioacetic acid (CH3COSH) as the major product. Therefore, the correct answer is B.