The reaction of 3-bromocyclohexene with NBS can theoretically form six isomeric dibromides; cis-3,6-; trans-3,6-; 3,3-; 1,3-; cis-3,4- and trans-3,4-dibromocyclohexene. When the reaction was run in CCl4, five dibromide product peaks were seen by GC-MS (M+ peaks at m/z = 238, 240, 242). The relative peak areas (listed in order of increasing retention time) showed no dependence on 3-bromocyclohexene conversion (32%; 2%; 51%; 12%; 1%). Recrystallization of the crude product gave pure trans-3,6-dibromocyclohexene verifying that the major product (51%) is this isomer. The 3,3- and trans-3,4- isomers were prepared through alternative synthesis protocols with the goal of identifying the other dibromide products of the reaction.

NBS bromination of 3-bromocyclohexene

251st National Meeting (2016)

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