Conformations and Structures of Ethoxycarbonyl Isothiocyanate Revealed by Rotational Spectroscopy

The ethoxycarbonyl isothiocyanate has been investigated by using supersonic jet Fourier transform microwave spectroscopy. Two sets of rotational spectra belonging to conformers TCC (with the backbone of C - C - O - C, C - O - C=O, and O - C(=O) - NCS being trans, cis, and cis arranged, respectively) and GCC ( gauche , cis, and cis arrangement of the C - C - O - C, C - O - C=O, and O - C(=O) - NCS) have been measured and assigned. The measurements of ^13 C, ^15 N and ^34 S mono-substituted species of the two conformers have also been performed. The comprehensive rotational spectroscopic investigations provide accurate values of rotational constants and ^14 N quadrupole coupling constants, which lead to structural determinations of the two conformers of ethoxycarbonyl isothiocyanate. For conformer TCC, the values of P_ \rmcc keep constant upon isotopic substitution, indicating that the heavy atoms of TCC are effectively located in the ab plane.