Ultraviolet Absorption and Rotatory Dispersion of 3-Methylcyclohexanone¹

Density-functional theory calculations of optical rotatory dispersion in the nonresonant and resonant frequency regions

“…The amplitude of the ORD for the 3R-boat-equatorial form of 3MCH is also significantly larger than for any of the other conformations. Since the experimental spectrum shows a clear positive Cotton curve, 11,12 it is clear that the solution contained a surplus of the chairequatorial conformation, which is also in agreement with it being lower in energy.…”

“…The ORD of 3Rmethylcyclohexanone ͑3MCH͒ in the chair and boat conformations and with an equatorial placement of the methyl group has been studied theoretically by Polavarapu and Zhao. 3 Their results have been compared with the corresponding experimental spectra 11,12 for the ͑ϩ͒-enantiomerthat is, the 3R-chair-equatorial form, which includes the resonant region of optical frequencies.…”

“…The use of the Hartree-Fock method for this organic molecule inflicts a well-known overestimation of the excitation energy. Thus, the Hartree-Fock transition wavelength is 252 nm, 3 which corresponds to an error in the transition energy of 0.75 eV relative to the experimentally observed wavelength of 297 nm, 11,12 making it impossible to perform accurate calculations of the ORD in the resonance region since the dispersion is largely determined by the excitation energies of the system. In Fig.…”

“…In addition to the problems with the divergences, the Hartree-Fock excitation energy was off by about 0.75 eV compared to experiment. 11,12 In this paper, we aim to rectify the problem of divergences in the mixed electric-dipole-magnetic-dipole polarizability tensor through the use of complex response functions. 13 The basic ansatz in this approach is to introduce a finite lifetime for the excited states, thereby obtaining a physically correct description of the molecular response also in the resonant regions.…”

Optical activity in ketones. The rotatory dispersion and circular dichroism of m-methyl cyclohexanone and of pulegone in their ketonic absorption bands

“…Earlier measurements of absorption and rotatory dispersion with less pure samples led to conflicting and extraordinary results, and the observations only became uniformly reproducible when Professor Read's very pure material was available. There is no doubt that the optical properties of the compound are seriously affected by the presence of even small traces of impurity; and it is not surprising therefore that the data now recorded do not agree with those published recently by French and Naps (1936), who describe their specimen only as " purified through its bisulphite addition compound".…”