STERIC INHIBITION OF ?-ELECTRON DELOCALIZATION IN 1,3-DIENES. CIRCULAR DICHROISM OF METHYLISOPULEGENE AND 3,8-p-MENTHADIENE

Article abstract of DOI:10.1016/S0040-4020(01)97684-7

The conjugated diene, "methylisopulegene" (1, 1-isopropenyl-2,4-dimethyl-1-cyclohexene), exhibits a CD Cotton effect (CE) with Δε₂₁₇ = +1.77 but no UV maximum down to 200 nm; whereas, the structurally related conjugated diene, 3,-8-p-menthadiene (2, 1-isopropenyl-4-methyl-1-cyclohexene), exhibits a more normal UV maximum at 232 nm (ε = 17,300) and a CE with Δε₂₄₀ = +2.56.