| Abstract
| - The possible competition of Z/E versus hydrogen-shift isomerization in (E)-5-phenyl-3-penten-2-one (E-1)and (E)-5-phenyl-4-penten-2-one (E-2) was studied, both experimentally and theoretically. Iodine-catalyzedisomerization experiments and computational modeling studies show that the equilibrated system consistspredominantly of E-1 and E-2, with E-2 in moderate excess, and with no detectable amounts of the Z (cis)diastereoisomers. Density functional theory (DFT) calculations corroborated the free energy difference(Δrand Δrwere −0.7 and −1.1 kcal mol-1, respectively), and computations of Boltzmann-weighted 1H NMR spectra were found to be useful in confirming the assignment of the isomers. The relevanceof this equilibrium to earlier work on double-bond stabilization is discussed.
|
