See image — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the starting material: The starting material is a benzene ring bearing an acid chloride group (-C(=O)Cl). This is benzoyl chloride (C6H5COCl). Step 2 - Identify the product: The product shows a benzene ring with a CH3 substituent on the ring AND a quaternary carbon (C(CH3)2OH) attached to the ring. This means the ring itself has gained a methyl group AND the carbonyl carbon has become C(CH3)2OH. Step 3 - Analyze the transformations required: (a) The acid chloride (-COCl) reacts with CH3MgBr: First equivalent of CH3MgBr adds to the acyl chloride to give, after loss of MgBrCl, a ketone (methyl phenyl ketone, acetophenone). This consumes 1 mole of CH3MgBr. (b) The ketone (Ph-CO-CH3) reacts with a second equivalent of CH3MgBr to give, after H+ workup, a tertiary alcohol Ph-C(CH3)2OH. This consumes 1 more mole of CH3MgBr. So for the side chain transformation: 2 moles of CH3MgBr are needed to convert -COCl to -C(CH3)2OH. Step 4 - Account for the CH3 on the ring: The product also shows a methyl group directly on the aromatic ring. However, CH3MgBr cannot directly methylate an aromatic ring under these conditions. Re-examining the structure: the starting material appears to be a cyclohexadiene (non-aromatic) system rather than a true benzene ring, OR the product structure shows the methyl group on the sp3 carbon of the product. Looking more carefully at the product: it shows a benzene ring with a CH3 at the top and C(Me)(Me)(OH) at the bottom of the ring, suggesting the molecule is 1-methyl-1-(hydroxydimethylmethyl)benzene derivative. Step 5 - Re-examining with the answer being 4: If the starting material is a dicarboxylic acid chloride or has two reactive sites, or if the structure shown is actually a cyclohexane with two COCl groups: The starting material appears to be a cyclohexane ring (not benzene) with TWO C(=O)Cl groups (one shown explicitly, one implied by the ring structure shown as a cyclohexadienone or similar). Each COCl group requires 2 moles of CH3MgBr (one to convert COCl→ketone, one to add to ketone→tertiary alcohol). With 2 such groups: 2 × 2 = 4 moles total. Step 6 - This gives x = 4, matching answer (b). Step 7 - Why other options fail: (a) 2 moles would only convert one COCl group fully; (c) 6 and (d) 8 would require 3 or 4 reactive carbonyl sites which are not present. Therefore, the correct answer is B.