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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Comparison of Cooperativity in CH...O and OH...O Hydrogen Bonds
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Comparison of Cooperativity in CH...O and OH...O Hydrogen Bonds

机译：CH ... O和OH ... O氢键中的协同作用比较

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摘要

The ability of one H-bond in a chain to affect others is assessed by comparing the CH...O bonds in ( and (HFCO)_n to the OH...O bonds in (H_2O)_n.Both sorts of interactions grow stronger,and the intermolecular distances shorter,as the number of monomers in the chain increases.The degree of cooperativity is generally proportional to the strength of the H-bond,although the CH...O bonds in (HFCO)_n display a disproportionately high degree of cooperativity.The cooperativity of OH..O and CH...O bonds is similar also with respect to electron density loss from the bridging hydrogen atom,and the amount of charge transferred from the proton-acceptor molecule to the donor.The covalent CH bonds are shortened upon H-bond formation,and the associated stretching frequencies undergo a blue shift,both opposite to what is observed in OH...O systems.These properties exhibit little indication of cooperativity for CH,while the OH bond stretches and red shifts of the OH frequencies are enhanced as n increases.NMR chemical shifts of the bridging proton likewise suggest that CH...O bonds are much less cooperative than OH...O.Cooperativity is reduced in all systems as the dielectric constant of a surrounding solvent is enhanced.
机译：通过比较（和（HFCO）_n中的CH ... O键与（H_2O）_n中的OH ... O键来评估链中一个H键影响其他键的能力。随着链中单体数量的增加，分子间的距离变得更强，而分子间的距离更短。尽管（HFCO）_n中的CH ... O键显示的比例不成比例，但协同程度通常与H键的强度成正比。 OH..O和CH ... O键的协同作用在桥接氢原子的电子密度损失以及从质子受体分子转移到供体的电荷量方面也相似。共价CH键在形成H键时会缩短，并且相关的拉伸频率发生蓝移，这与在OH ... O体系中观察到的相反。这些性质几乎没有迹象表明与CH的协同作用，而OH键OH频率的拉伸和红移随着n的增加而增强ses.NMR桥联质子的化学位移同样表明CH ... O键的协同作用远不如OH ... O。随着周围溶剂介电常数的提高，协同作用在所有体系中均降低。

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