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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ab Initio Study of Proton Transfer between Protonated Formohydroxamic Acid and Water Molecules
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Ab Initio Study of Proton Transfer between Protonated Formohydroxamic Acid and Water Molecules

机译：质子化羟肟酸与水分子之间质子转移的从头算研究

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摘要

Proton transfeg’ between protonated formohydroxamic acid (FAH)~ aki water molecules (H2O—FAH—Fi2O)~ is studied theoretically. in a proton-relay mechanism., fit cut,oayl oxygen in formohydroxamic acid (HCONHOH, FA) accepts a proton from the hydronium xa (1130’) and releases a proton either from the amine group (N—H) or the N-hydroxyl (N—OH) of formoluy&ozamic acid to another f120 molecule. The movement of the two protons is not simultaneous but thwiugh a aepwise process. The catalytic effect of the H20 molecule in reducing the proton-transfer barrier comed so the catalytic effect of pure formohydroxamic acid through intramolecular proton transfer is substantiaL ibe transfer barriers of the two protons in a relay process are asymmetric. The proton on either the amim gxu~ (N—H) or the N-hydroxyl (N—OH) of FAH~ will be transferred to the second H20 molecule, and the ir~m transfer is determined by the lengths RN...O and Ro...o, which are related to the distance between FAH’ and the second H20 molecule. At the same RN...O and Ro...o, the proton on amino group (N—H) has a zrar~er atrgy barrier lower than that of the proton on the N-hydroxyl site by about 4.1 kcallmol. If we elongate the distance between the two water molecules and let protonated FA shuttle freely as a proton carrier between the two water molecules, then the energy barrier for the movement of protonated FA increases slowly with the increase of the distance between two H20’s separated by no more than 10 A. However, the proton-transfer barrier between protonated FA and water is independent of the separated distance of the two waxer molecules.
机译：理论上研究了质子化的甲酸羟肟酸（FAH）〜和水分子（H2O-FAH-Fi2O）〜之间的质子转化。在质子-中继机制中，合适的馏分，甲酸羟肟酸（HCONHOH，FA）中的脂酰氧从氢合xa（1130'）接收质子，并从胺基团（NH）或N-释放质子甲酸和氨基甲酸的羟基（N-OH）形成另一个f120分子。两个质子的运动不是同时发生的，而是经过一个先验的过程。 H20分子在减少质子转移势垒方面起了催化作用，因此通过分子内质子转移，纯甲酸羟肟酸的催化作用是实质性的，因为在中继过程中两个质子的转移势垒是不对称的。 FAH〜的氨基（NH）或N-羟基（NH）上的质子将转移到第二个H20分子上，ir_m转移由长度RN确定。 O和Ro ... o，它们与FAH'和第二个H20分子之间的距离有关。在相同的RN ... O和Ro ... o下，氨基（NH）上的质子具有比N-羟基位点上的质子低的zrarerer能垒，约为4.1kcallmol。如果我们拉长两个水分子之间的距离并使质子化的FA作为两个水分子之间的质子载体自由穿梭，则质子化的FA运动的能垒会随着两个H2O之间的距离的增加而缓慢增加，而没有大于10A。但是，质子化FA和水之间的质子转移势垒与两个蜡化分子的分隔距离无关。

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