See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the reactive sites: The starting material has two alkene-containing side chains on an ortho-disubstituted benzene ring bearing an OMe group. One chain is a (E)-hex-2-en-1-yl group (an internal, disubstituted trans alkene), and the other is a 4-pentenoyl group containing a terminal (monosubstituted) alkene as well as a ketone carbonyl. Step 2 - Reactivity of MCPBA toward different functional groups: MCPBA is an electrophilic peracid that epoxidizes alkenes. Its reactivity toward alkenes follows the order: more electron-rich (more substituted) alkenes react faster than less substituted ones. Additionally, MCPBA can perform Baeyer-Villiger oxidation on ketones, but this is generally slower and requires more forcing conditions than simple alkene epoxidation. Step 3 - Compare the two alkenes: The internal trans alkene in the hex-2-en-1-yl chain is disubstituted and more electron-rich than the terminal alkene in the pentenoyl chain. Moreover, the terminal alkene of the pentenoyl chain is electron-poor because it is conjugated with (or adjacent to) the electron-withdrawing ketone carbonyl, making it less reactive toward electrophilic epoxidation. Therefore, under these conditions (75% yield, presumably 1 equivalent of MCPBA), the more electron-rich internal alkene of the hex-2-en-1-yl chain is selectively epoxidized. Step 4 - Identify product B: Option (b) shows the internal double bond of the hex-2-en-1-yl chain converted to an epoxide, while the terminal alkene of the pentenoyl chain remains intact. This is consistent with selective epoxidation of the more electron-rich, more substituted alkene. Step 5 - Why other options fail: - Option (a) shows epoxidation of the terminal alkene on the keto chain (less reactive, electron-poor) while leaving the internal alkene intact - opposite to expected selectivity. - Option (c) shows a Baeyer-Villiger type rearrangement of the ketone, which would require different/more forcing conditions and MCPBA would preferentially epoxidize the electron-rich alkene first. - Option (d) is eliminated because option (b) correctly describes the product. Therefore, the correct answer is B.