James Andrew M, Laconsay Croix J, Galbraith John Morrison
Department of Chemistry, Biochemistry, and Physics, Marist College , 3399 North Road, Poughkeepsie, New York 12601, United States.
J Phys Chem A. 2017 Jul 13;121(27):5190-5195. doi: 10.1021/acs.jpca.7b02988. Epub 2017 Jun 30.
Bond dissociation energies and resonance energies for HA-BH molecules (A, B = H, C, N, O, F, Cl, Li, and Na) have been determined in order to re-evaluate the concept of electronegativity in the context of modern valence bond theory. Following Pauling's original scheme and using the rigorous definition of the covalent-ionic resonance energy provided by the breathing orbital valence bond method, we have derived a charge-shift corrected electronegativity scale for H, C, N, O, F, Cl, Li, and Na. Atomic charge shift character is defined using a similar approach resulting in values of 0.42, 1.06, 1.43, 1.62, 1.64, 1.44, 0.46, and 0.34 for H, C, N, O, F, Cl, Li, and Na, respectively. The charge-shift corrected electronegativity values presented herein follow the same general trends as Pauling's original values with the exception of Li having a smaller value than Na (1.57 and 1.91 for Li and Na respectively). The resonance energy is then broken down into components derived from the atomic charge shift character and polarization effects. It is then shown that most of the resonance energy in the charge-shift bonds H-F, HC-F, and Li-CH and borderline charge-shift H-OH is associated with polarity rather than the intrinsic atomic charge-shift character of the bonding species. This suggests a rebranding of these bonds as "polar charge-shift" rather than simply "charge-shift". Lastly, using a similar breakdown method, it is shown that the small effect the substituents -CH, -NH, -OH, and -F have on the resonance energy (<10%) is mostly due to changes in the charge-shift character of the bonding atom.
为了在现代价键理论的背景下重新评估电负性的概念，已确定了HA - BH分子（A、B = H、C、N、O、F、Cl、Li和Na）的键解离能和共振能。遵循鲍林的原始方案，并使用呼吸轨道价键法提供的共价 - 离子共振能的严格定义，我们推导出了H、C、N、O、F、Cl、Li和Na的电荷转移校正电负性标度。使用类似的方法定义原子电荷转移特征，得出H、C、N、O、F、Cl、Li和Na的值分别为0.42、1.06、1.43、1.62、1.64、1.44、0.46和0.34。本文给出的电荷转移校正电负性值遵循与鲍林原始值相同的一般趋势，但Li的值小于Na（Li和Na分别为1.57和1.91）。然后将共振能分解为由原子电荷转移特征和极化效应得出的分量。结果表明，电荷转移键H - F、HC - F和Li - CH以及临界电荷转移键H - OH中的大部分共振能与极性有关，而不是与键合物种的固有原子电荷转移特征有关。这表明将这些键重新命名为“极性电荷转移”而不是简单的“电荷转移”。最后，使用类似的分解方法表明，取代基 - CH、 - NH、 - OH和 - F对共振能的小影响（<10%）主要是由于键合原子电荷转移特征的变化。
