See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: This reaction involves the Prins reaction (or a related acid-catalyzed addition of formaldehyde to an alkene). Under acidic aqueous conditions (H+, H2O), an alkene reacts with formaldehyde (HCHO) via a Prins-type mechanism. Step 1 - Protonation of the alkene: 1-methylcyclohex-1-ene is protonated by H+ to give the more stable tertiary carbocation at C1 (the carbon bearing the methyl group), following Markovnikov's rule. Step 2 - Electrophilic addition to formaldehyde: The tertiary carbocation at C1 attacks the formaldehyde (HCHO) acting as a nucleophile toward the carbonyl, or alternatively, the protonated formaldehyde (oxocarbenium ion, CH2=OH+) acts as the electrophile attacking the alkene. In the Prins mechanism, protonated HCHO (CH2=OH+) is the electrophile. The alkene's pi electrons attack the electrophilic carbon of CH2=OH+, placing the positive charge on the more substituted carbon (C1, tertiary position) per Markovnikov selectivity. Step 3 - Nucleophilic capture: Water attacks the tertiary carbocation at C1, giving an alcohol (OH) at C1. Simultaneously, the oxygen of the CH2OH group at C2 (from formaldehyde addition) is deprotonated. Wait - re-examining: In the Prins reaction with HCHO and H+, the alkene acts as nucleophile toward protonated formaldehyde. The more nucleophilic end of the double bond (C2, less substituted) attacks HCHO, placing the carbocation on C1 (tertiary). Water then traps the C1 carbocation to give OH at C1. This results in: C1 has methyl + OH, and C2 has CH2OH. This matches option (b): the cyclohexane ring with methyl at C1, OH at C1, and CH2OH at C2 (drawn as 1-methyl-1-hydroxycyclohexane-2-methanol). Why other options fail: - Option (a): A simple diol at C1,C2 would require oxidation, not formaldehyde addition. - Option (c): Has CH2OH at C1 and OH at C2, which would require opposite regiochemistry (carbocation at C2, less stable secondary), disfavored. - Option (d): Has two OH-containing groups at C1 only, inconsistent with Prins mechanism. Therefore, the correct answer is B.