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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Hydrogen Bonding of Phenols or Their Radical Cations with Water or Ammonia: Substituent Effects and the Influence on Phenol Oxidation
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Hydrogen Bonding of Phenols or Their Radical Cations with Water or Ammonia: Substituent Effects and the Influence on Phenol Oxidation

机译：苯酚或其自由基与水或氨的氢键结合：取代基效应及其对苯酚氧化的影响

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摘要

We did UB3LYP/6-31 ++g~(**) and ROMP2/6-311 ++g~(**) calculations on the hydrogen bonding of para-substituted phenols and their radical cations with water and ammonia. It was found that the magnitudes of the proton affinities increase in the order water (165 kcal/mol) < ammonia (204 cal/mol) ≈phenoxyl radicals (193-235 kcal/mol) < phenolate anions (321-352 kcal/mol). The slopes of the proton affinities against the substituent σ_p constants are about 22 and 15 kcal/mol for phenoxyl radicals and phenolate anions. It was also found that the slopes of the binding energies against the substituent σ_P constants decrease in the order phenol-water complex (1.1 kcal/mol) < phenol-ammonia complex (1.4 kcal/mol) < phenol radical cation-water complex (4.1 kcal/mol) < phenol radical cation-ammonia complex (9.3 kcal/mol). The structure of the substituted phenol radical cation-ammonia complex was found to rely on the proton affinity of the corresponding phenoxyl radical. When the proton affinity is larger than 214 kcal/mol, the non-proton-transferred form is the only minimum on the potential energy surface. When the proton affinity is ambler than 210 kcal/mol, the proton-transferred form is the only minimum. The only complex for which both the proton-transferred and non-proton-transferred forms are minima was found for p-hydroxylphenol radical cation. On the other hand, all the phenol radical cation complexes with water have the non-proton-transferred form as the only minimum on the potential surface. Hydrogen bonding to ammonia was found to lower the adiabatic oxidation potentials of phenols by 0.5-1.2 eV. Hydrogen bonding to water was found to lower the adiabatic oxidation potentials of phenols by 0.4-0.6 eV. In general, a phenol substituted with a more electron-withdrawing group shows larger reduction in the adiabatic oxidation potential when complexed to water or ammonia.
机译：我们进行了UB3LYP / 6-31 ++ g〜（**）和ROMP2 / 6-311 ++ g〜（**）的计算，计算出对位取代的苯酚及其自由基阳离子与水和氨的氢键。已发现质子亲和力的大小按水（165 kcal / mol）<氨（204 cal / mol）≈苯氧基（193-235 kcal / mol）<酚盐阴离子（321-352 kcal / mol）的顺序增加）。对于苯氧基自由基和酚盐阴离子，质子亲和力相对于取代基σ_p常数的斜率约为22和15kcal / mol。还发现结合能对取代基σ_P常数的斜率按苯酚-水络合物（1.1 kcal / mol）<苯酚-氨络合物（1.4 kcal / mol）<苯酚自由基阳离子-水络合物（4.1 kcal / mol）<酚自由基阳离子-氨络合物（9.3 kcal / mol）。发现取代的酚基阳离子-氨络合物的结构依赖于相应的苯氧基基团的质子亲和力。当质子亲和力大于214 kcal / mol时，非质子转移形式是势能表面上的唯一最小值。当质子亲和力大于210 kcal / mol时，质子转移形式是唯一的最小值。发现对羟基苯酚自由基阳离子的质子转移和非质子转移形式都最小的复合物。另一方面，所有酚自由基阳离子与水的络合物具有非质子转移形式，作为在势能表面上的唯一最小值。发现与氨的氢键将苯酚的绝热氧化电位降低了0.5-1.2 eV。发现与水的氢键使苯酚的绝热氧化电位降低0.4-0.6 eV。通常，当与水或氨络合时，被更多的吸电子基团取代的苯酚显示出绝热氧化电位的较大降低。

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