See image — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

Concept: Solvolysis of a secondary benzylic triflate (OTf) under nucleophilic conditions. Step 1 – Identify the substrate. The starting material is a secondary benzylic triflate: the carbon bearing OTf is attached to a phenyl group and an ethyl group, making it a secondary benzylic carbon with the S-configuration. Triflate (OSO2CF3) is one of the best leaving groups known in organic chemistry. Step 2 – Identify the reagent. CH3OH (methanol) at mild heat (30 °C) is the solvent/nucleophile. Methanol is a weak nucleophile but the reaction is run in excess methanol (solvolysis conditions). At 30 °C, the conditions do not strongly favor elimination over substitution. Step 3 – Reaction pathway. Because the carbon bearing the triflate is secondary and benzylic, ionization to form a stabilized benzylic carbocation is very facile (triflate is an excellent leaving group). The benzylic carbocation formed is stabilized by resonance with the phenyl ring. In the presence of a nucleophilic solvent (methanol), SN1-type solvolysis (or direct SN2) leads to substitution. Methanol acts as the nucleophile, attacking the benzylic carbocation (or the back face in SN2), displacing the triflate and forming the methyl ether product: PhCH(OCH3)(CH2CH3). Step 4 – Why substitution predominates over elimination at 30 °C. Elimination (E1 or E2) is favored by strong bases and/or high temperatures. Methanol at only 30 °C is a weak base; the mild temperature and nucleophilic solvent favor substitution (SN1 solvolysis) rather than elimination to give styrene derivative (option b). Step 5 – Evaluate other options. - Option (b) beta-methylstyrene: This would require elimination (E1 or E2). Under these mild conditions (weak base, 30 °C), elimination is not the predominant pathway. - Option (c) PhCH(OSO2CH3)(Et): This would require exchange of the triflate for a mesylate group. Methanol cannot act as a sulfonyl transfer agent; this product makes no chemical sense under these conditions. - Option (d) None of these: Incorrect because option (a) is the expected product. Step 6 – Conclusion. The predominant product is the methyl ether PhCH(OCH3)(CH2CH3), formed by SN1 solvolysis of the benzylic triflate with methanol as nucleophile. This corresponds to option (a). Therefore, the correct answer is A.