A JET-COOLED ROTATIONAL STUDY OF EPHEDRINE AND P-METOXYPHENYLAMINE

Abstract

The first gas phase rotational spectrum of ephedrine, a synthetic analog of the neurotransmitter adrenaline with similar effects on the cardiovascular system, has been observed using a molecular beam Fourier transform microwave spectrometer. Solid ephedrine (m.p. 36 $^{irc}$C) was vaporized by heating it in a reservoir located in pulsed valve. In these conditions the three lowest-energy conformers of ephedrine have been detected. Hyperfine structure due to the presence of a $^{14}$N nucleus ($I=1$) has been observed for all conformers, allowing the unambiguous assignment of their spectra. Microwave spectroscopy in supersonic jets has been also applied to the conformational and structural analysis of the p-methoxiphenylethylamine molecule. The rotational spectra of the seven conformers previously observed by Pratt \textit{et al}.}, \textbf{4}, 5244 (2002) } have been unambiguously assigned on the basis of the values of their rotational and nuclear quadrupole coupling constants. The predictions of \textit{ab initio} calculations have been used as guidelines.