Microwave Spectroscopic and Theoretical Examination of Allyl Isothiocyanate Conformational Space

Abstract

A spectroscopic analysis of allyl isothiocyanate (CH 2 = CHCH 2 NCS) was conducted via chirped-pulse and Balle-Flygare Fourier Transform microwave (FTMW) spectroscopy in the 7-25 GHz range. Rotational transitions associated with the different conformers were assigned based on information gathered from quantum-chemical calculations computed at B3LYP-D3(BJ) and MP2 levels of theory using the Dunning cc-pVTZ basis set. The results showed the existence of two conformers, the gauche conformer, which was reported in previous work a as well as the first reported existence of a second conformer which corresponds to the global minimum. Spectroscopic assignments included transitions due to both parent conformers, 34 S, 13 C and 15 N singly substituted isotopic species as well as hyperfine splitting due to the presence of 14 N.