Knowledge Bank

Evidence is presented that the alpha-phenyl ketimine ion behaves spectroscopically like the alpha-phenyl carbonyl group which has been demonstrated to give rise to a long wavelength electronic transition of unexpectedly high extinction.1,2 The spectrum of the stable alpha-phenyl ketimine ion, isomethadon ketimine hydrochloride, gives rise to a strong long wavelength band ($ϵ=5200$ at 256 mu) compared with the end spectrum only of the free base at shorter wavelengths. The corresponding spectra of the ion and free base of a stable alkyl-ketimine, fencholyl isopropyl (isopropyl 1-methyl-3-isopropylcyclopentyl) ketimine and some aryl-conjugated ketimines (phenyl isobutyl ketimine, diphenyl ketimine and phenyl o-tolyl ketimine) are presented for comparison. These spectra clearly support the validity of the above-described alpha-phenyl ketimine interaction band. The long wavelength band in the alpha-phenyl ketimine ion reported here and the alpha-phenyl carbonyl formerly $reported1,2$ is interpreted from these data as arising from a $\pi$ electron transition.