See image — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the starting material: The starting material is 2-(bromomethyl)oxirane, i.e., an epoxide ring (oxirane) with a -CH2Br group attached. The structure is: the oxirane ring consists of CH2 and CH connected by an oxygen bridge, and the CH bears a -CH2Br substituent. Step 2 - Reaction with Mg in dry ether to form Grignard reagent (A): The -CH2Br reacts with Mg to form the Grignard reagent: the oxirane ring with -CH2MgBr. This is (bromomethyl)oxirane converted to (oxiran-2-yl)methylmagnesium bromide. The epoxide ring remains intact under Grignard formation conditions. Step 3 - Reaction of Grignard reagent (A) with CH3I: The Grignard reagent RMgBr reacts with CH3I (an alkyl halide) via an SN2 coupling reaction. However, with epoxide-containing Grignard reagents and alkyl halides, an intramolecular or intermolecular reaction can occur. The Grignard carbon (carbanion character on CH2-) attacks the electrophilic carbon of CH3I. But simultaneously, the epoxide can undergo ring-opening. Step 4 - The actual reaction pathway: The Grignard reagent from (bromomethyl)oxirane with CH3I undergoes a reaction where the carbanion attacks CH3I giving -CH2-CH3 from the CH2MgBr end, BUT the epoxide ring opens. The epoxide oxygen, activated by the reaction conditions, opens to give an allylic/homoallylic system. The product observed is H2C=CH-CH2-O-CH3. This arises because the Grignard with the oxirane undergoes beta-elimination of the epoxide to give an allyl Grignard (H2C=CH-CH2MgBr via ring opening of the epoxide), which then reacts with CH3I to give allyl methyl ether: H2C=CH-CH2-O-CH3... Re-examining: The Grignard reagent is oxiranylmethyl MgBr. This is known to rearrange: the epoxide ring opens with the carbanion to give an allylic alkoxide Grignard: H2C=CH-CH2-OMgBr (homoallylic rearrangement / beta-elimination). This allylic alkoxide then reacts with CH3I at the oxygen (since oxygen is the nucleophile in the alkoxide) to give H2C=CH-CH2-O-CH3 (allyl methyl ether). Step 5 - Why other options fail: (a) Would require the epoxide to remain intact and a simple C-C coupling, but the epoxide opens under these conditions. (b) CH3-O-CH2-CH2-CH3 would require different connectivity. (d) Propylene oxide would require loss of the CH2 group. Only option (c) H2C=CH-CH2-O-CH3 is consistent with the rearrangement of the oxiranylmethyl Grignard to an allylic alkoxide MgBr, followed by O-methylation with CH3I. Therefore, the correct answer is C.