基于转动光谱研究异硫氰酸乙氧羰基酯的分子结构和构象平衡

Conformations and Structures of Ethoxycarbonyl Isothiocyanate Revealed by Rotational Spectroscopy

本文利用超声射流-傅里叶变换微波波谱技术对异硫氰酸乙氧羰基酯的转动光谱进行了研究.实验测定了异硫氰酸乙氧羰基酯的两个构象的转动光谱,即构象TCC(C-C-O-C、C-O-C=O、O-C(=O)-NCS骨架分别为反式、顺式、顺式朝向)和构象GCC(C-CO-C、C-O-C=O、O-C(=O)-NCS骨架分别为交叉式、顺式、顺式朝向).此外,在自然丰度下测定了这两个构象的13C、15N和34S的单取代同位素异构体的转动光谱,获得了精确的转动常数和14N核四极耦合常数的数值.基于实验测定的转动常数计算得到了异硫氰酸乙氧羰基酯的分子结构参数.对于构象TCC,同位素取代未改变其Pcc值,表明该构象具有Cs对称性,即重原子位于分子的ab平面上.

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 of13C,15N and34S mono-substituted species of the two conformers have also been performed.The comprehensive rotational spectroscopic investigations provide accurate values of rotational constants and14N quadrupole coupling constants,which lead to structural determinations of the two conformers of ethoxycarbonyl isothiocyanate.For conformer TCC,the values of Pcckeep constant upon isotopic substitution,indicating that the heavy atoms of TCC are effectively located in the ab plane.