Matrix Photochemical Study and Conformational Analysis of CH3C(O)NCS and CF3C(O)NCS

Conformations and non-covalent interactions of cyclohexyl isothiocyanate and its water complex

The conformational equilibria of cyclohexyl isothiocyanate and its complex with water were studied by microwave spectroscopy combined with theoretical calculations. For the bare cyclohexyl isothiocyanate, the rotational spectra of the two conformers, namely a-trans and e-trans, were measured and analyzed. Additional mono-substituted isotopologues of two ¹³C and one ³⁴S of a-trans and e-trans were also measured, which result in an accurate structural determination of the two conformers. For the binary complex with water, the rotational spectra were measured for the monohydrates of both a-trans and e-trans conformers. Water isotopologues were also detected for the monohydrates. All the measured rotational spectra show ¹⁴N quadrupole coupling hyperfine structures. Water molecule prefers linking to the isothiocyanate group through a O_wH⋯S hydrogen bond and forming two CH⋯O_w hydrogen bonds with the oxygen atom of water acting as a proton acceptor. The non-covalent bonding features of the monohydrates were revealed by natural bond orbital analysis and symmetry-adapted perturbation theory analysis.

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 13C, 15N and 34S mono-substituted species of the two conformers have also been performed. The comprehensive rotational spectroscopic investigations provide accurate values of rotational constants and 14N quadrupole coupling constants, which lead to structural determinations of the two conformers of ethoxycarbonyl isothiocyanate. For conformer TCC, the values of Pcc keep constant upon isotopic substitution, indicating that the heavy atoms of TCC are effectively located in the ab plane.