Consider the following reaction sequences that yield carboxylic acids as major organic products: (A) PhMgBr + CO ₂ Dry ether H ₃ O ⁺ Product A (B) CH ₃ CH ₂ MgBr + CO ₂ Dry ether H ₃ O ⁺ Product B (C) ClCH ₂ CN H ₃ O ⁺/ Product C (D) CH ₃ C CH KMnO ₄, H ⁺/ Product D Which of the given reaction sequences produces the major product with the highest pK _ a value?

Step-by-step solution

Product A is benzoic acid ( PhCOOH ). Product B is propanoic acid ( CH ₃ CH ₂ COOH ). Product C is chloroacetic acid ( ClCH ₂ COOH ). Product D is acetic acid ( CH ₃ COOH ). The acidic strength depends on the stability of the conjugate base. The + I effect of alkyl groups destabilizes the carboxylate ion, decreasing acidity. The ethyl group in propanoic acid has a stronger + I effect than the methyl group in acetic acid. The - I effect of chlorine makes chloroacetic acid the strongest. Benzoic acid is stronger than