Steric effects of a nitro group on the optical stabilities of 2,2′-bridged and unbridged biphenyls
作者:D. Muriel Hall、Teresa M. Poole
DOI:10.1039/j29660001034
日期:——
in solution at room temperature. Racemisation data for the azepinium picrate from a 6-nitrobiphenyl, in acetone, show that it has an unusually high Arrhenius parameter A. The energy barrier to racemisation is discussed in relation to that in similar bridged compounds, and some apparent discrepancies between polarimetric results and those obtained by n.m.r. spectroscopy are pointed out. A related unbridged
从4-和6-硝基-2,2'-双溴甲基联苯制备季铵盐。在具有对硝基基团的化合物中未观察到光学活性,但是衍生自邻硝基化合物的合适的盐在室温下显示出溶液中的旋转。用于从6-硝基联苯的氮杂苦味酸盐,丙酮外消旋化数据,表明它具有不寻常的高阿列纽斯参数甲。讨论了外消旋作用的能垒与类似桥联化合物的能垒有关,指出了极化结果与通过核磁共振光谱法获得的结果之间的某些明显差异。已经制备了相关的未桥联的双季盐,并获得了旋光性。光学稳定性最高可达。 90°,但是非常低的比旋光度到目前为止阻止了对其消旋作用的定量研究。