作者:Martin J. Deetz、Christopher C. Forbes、Marco Jonas、Jeremiah P. Malerich、Bradley D. Smith、Olaf Wiest
DOI:10.1021/jo025554u
日期:2002.5.1
The barrier for rotation about an N-alkylcarbamate C(carbonyl)-N bond is around 16 kcal/mol. In the case of an N-phenylcarbamate, the rotational barrier is lowered to 12.5 kcal/mol, but with N-(2-pyrimidyl)carbamates the barriers are so low (<9 kcal/mol) that the syn and anti rotamers cannot be observed as separate signals by 500 MHz NMR spectroscopy at 183 K. X-ray and computational data show that
围绕N-烷基氨基甲酸酯C(羰基)-N键旋转的屏障为约16kcal / mol。在使用N-苯基氨基甲酸酯的情况下,旋转势垒降低至12.5 kcal / mol,但是使用N-(2-嘧啶基)氨基甲酸酯时,势垒非常低(<9 kcal / mol),因此合成和反旋转异构体不能在183 K处通过500 MHz NMR光谱作为单独的信号观察到。X射线和计算数据表明,N-(2-嘧啶基)氨基甲酸酯的C(羰基)-N键平均比相关N-长0.03A。氨基甲酸酯。计算结果表明,由于嘧啶基环的吸电子能力增强,C(羰基)-N键单键特性增加的影响的起因。