See image — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

Step 1 - Understand the reaction mechanism. When a carboxylic acid reacts with an organolithium reagent (CH3Li), the first equivalent of CH3Li acts as a base and deprotonates the acidic OH of the carboxylic acid (pKa ~5), forming a lithium carboxylate salt and releasing CH4. This consumes 1 equivalent of CH3Li. Step 2 - Formation of the ketone (Compound A). A second equivalent of CH3Li then adds to the lithium carboxylate (acting as a nucleophile at the carbonyl carbon), forming a dilithio tetrahedral intermediate (a gem-diolate). Upon aqueous workup (NH4Cl/H2), this intermediate collapses to give the ketone (Compound A). This step requires 1 more equivalent of CH3Li. So far: 2 equivalents of CH3Li are needed to convert the carboxylic acid to the ketone. Step 3 - Identify Compound B (the side reaction). The ketone (Compound A) formed in situ can react with a third equivalent of CH3Li by nucleophilic addition to the carbonyl, giving a tertiary alcohol after workup. This is the side reaction that produces Compound B (a tertiary alcohol). This consumes 1 more equivalent of CH3Li. Step 4 - Account for the hydroxyl group in the substrate. The starting material also contains a free hydroxyl group (-OH) at the other end of the chain (HOCH2CH2-). This -OH is also acidic and will be deprotonated by CH3Li before any nucleophilic addition occurs. This consumes 1 additional equivalent of CH3Li. Step 5 - Total equivalents of CH3Li required. - 1 equiv to deprotonate the free alcohol (-OH group) - 1 equiv to deprotonate the carboxylic acid (-COOH) - 1 equiv for nucleophilic addition to form ketone - Since both products A and B form (side reaction also occurs), the reaction mixture requires excess CH3Li to drive the side reaction as well; however, the minimum x needed to explain both products forming is 3 equivalents for the main pathway plus the alcohol deprotonation = 3 total for giving the ketone, but Compound B forms from further reaction. Re-evaluating: The substrate has one -OH and one -COOH: - 1st equiv CH3Li: deprotonates -OH → lithium alkoxide - 2nd equiv CH3Li: deprotonates -COOH → lithium carboxylate - 3rd equiv CH3Li: nucleophilic addition to carboxylate → ketone after workup (Compound A) For the side product (Compound B, tertiary alcohol), the ketone must react with a 4th equivalent of CH3Li. But since x represents the total equivalents used in the reaction (and both A and B form), x = 3 gives predominantly ketone with some side product due to the ketone being reactive toward the excess reagent. With x = 3: deprotonate -OH (1 equiv), deprotonate -COOH (1 equiv), add to carboxylate (1 equiv) → all CH3Li consumed, ketone forms. Yet 37% side product forms, meaning some ketone reacts further. This is consistent with x = 3 where the reagent is not perfectly controlled and partial over-addition occurs. The question asks for the value of x that gives this specific product distribution. With x = 3 equivalents, the two deprotonations consume 2 equivalents, and 1 equivalent remains for addition to give ketone — but under these conditions the ketone partially reacts further, giving the observed 63:37 ratio. This matches option (b) 3. Why other options fail: - x = 2: Not enough to deprotonate both OH and COOH and still have nucleophilic addition. - x = 4 or 5: Would give predominantly the tertiary alcohol (Compound B), not predominantly ketone (63% A). Therefore, the correct answer is B.