THE MICROWAVE-SPECTRUM AND MOLECULAR-STRUCTURE OF ETHYLISOCYANATE

We have remeasured the spectrum of the isotopically most abundant spec ies of ethylisocyanate ((CH3CH2NCO)-C-12-C-12-N-14-C-12-O-16), and ass igned for the first time the spectra of all C-13-, N-15-, and O-18-mon osubstituted isotopomers in their respective natural abundances employ ing pulsed molecular beam microwave Fourier transform spectroscopy. We used these data to determine the heavy atom r(s) and r(o) structure w here the most interesting structural parameters, the C-N-C and N-C-O a ngles, were found to be 138.5-degrees and 176-degrees, with the oxygen atom trans to the ethyl group. Additionally we obtained improved valu es of the N-14 quadrupole coupling constants (in MHz) chi(aa) = 2.5488 (6), chi(bb) = -1.1717(8), and chi(cc) = -1.3771(8) of the (CH3CH2NCO) -C-12-C-12-N-14-C-12-O-16 species. From the variation of the coupling constants with isotopic substitution, we also determined the angular p osition of the coupling tensor in the inertial axis system.