The Basicity of Unsaturated Hydrocarbons as Probed by Hydrogen-Bond-Acceptor Ability: Bifurcated NH<sup>+</sup>⋅⋅⋅π Hydrogen Bonding
作者:Evgenii S. Stoyanov、Irina V. Stoyanova、Christopher A. Reed
DOI:10.1002/chem.200800337
日期:2008.9.8
bifurcated N--H+...pi hydrogen bonds, respectively. Bifurcated hydrogen bonds to unsaturated hydrocarbons have not been observed previously. The unsaturated hydrocarbons studied include benzene and methylbenzenes, fused-ring aromatics, alkenes, conjugated dienes, and alkynes. From the magnitude of the redshifts in the N--H stretching frequencies, Delta nuNH, a new scale for ranking the pi basicity of unsaturated
[Oct3NH+]B(C6F5)4 (-) 类型的接触离子对中的阴离子 (A(-)) 被不饱和烃 (L) 竞争性取代,符合平衡 Oct3NH+...A(-) + nL 右箭头高于左箭头 [Oct3NH+...Ln]A(-) 已在 CCl4 中进行了研究。根据平衡常数 K 和 nuNH 向低频的位移,已确定形成 n=1 和 2 的络合 Oct3NH...+Ln 阳离子,并具有单齿和分叉的 N--H+...分别为 pi 氢键。以前没有观察到与不饱和烃的分叉氢键。研究的不饱和烃包括苯和甲苯、稠环芳烃、烯烃、共轭二烯和炔烃。根据 N--H 伸缩频率红移的大小,Delta nuNH,提出了一种对不饱和烃的 pi 碱度进行排序的新尺度:稠环芳烃