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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 Intramolecular Proton Transfer in Formohydroxamic Acid
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Ab Initio Study of Intramolecular Proton Transfer in Formohydroxamic Acid

机译：从头算研究甲酸羟肟酸中分子内质子转移

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摘要

Interconversion of five isomeric tautomers of formohydroxamic acid via intramolecular proton transfer has been examined by ab initio theoretical calculation. The transfer potential surfaces, the global isomeric structures, and the transition geometries of intramolecular proton transfer were determined by the MP2/6-31+G~(**) level of calculation. The energy was further analyzed by a single point calculation, MP2/6-31++G~(**)//MP2/6-31+G~(**), and the use of G2 theory. Not counting the unstable charge separating species, the order of stability of these tautomers calculated at the HF level was 1E > 1Z > 2Z > 2E, and it shifted to 1Z > 1E > 2Z > 2E at the MP2 level, where 1Z and 1E are keto forms, while 2Z and 2E are iminol forms. Further investigation using G2 theory redirects the order to be 1Z > 2Z > 1E > 2E. The strength of the intramolecular hydrogen bond and the effect of dipole moment are the two major factors to dominate the acidity of formohydroxamic acid. Judging from the transition barrier of intramolecular proton-transfer we believe that formohydroxamic acid in dissociating proton in the gas phase is an N-acid.
机译：通过从头算的理论计算，已经研究了五羟肟酸的五个异构体互变异构体通过分子内质子转移的相互转化。分子内质子转移的转移势能面，整体异构体结构和过渡几何构型由MP2 / 6-31 + G〜（**）计算得出。通过单点计算MP2 / 6-31 ++ G〜（**）// MP2 / 6-31 + G〜（**）并使用G2理论进一步分析了能量。不计算不稳定的电荷分离物种，这些互变异构体在HF浓度下的稳定性顺序为1E> 1Z> 2Z> 2E，在MP2浓度下转移到1Z> 1E> 2Z> 2E，其中1Z和1E为酮形式，而2Z和2E是亚氨基形式。使用G2理论的进一步研究将顺序重定向为1Z> 2Z> 1E> 2E。分子内氢键的强度和偶极矩的影响是支配甲氧肟酸酸度的两个主要因素。从分子内质子转移的过渡壁垒来看，我们认为气相中离解质子的甲氧肟酸是一种N-酸。

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