Theoretical Calculation of Substituent Effects on the O−H Bond Strength of Phenolic Antioxidants Related to Vitamin E
Theoretical Calculation of Substituent Effects on the O−H Bond Strength of Phenolic Antioxidants Related to Vitamin E
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DOI：
10.1021/ja963378z
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发表时间：
1997-05
影响因子：
15
通讯作者：
J. Wright;David Carpenter;A. J. McKay;K. Ingold
中科院分区：
文献类型：
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作者：
J. Wright;David Carpenter;A. J. McKay;K. Ingold
对苯酚和大量被甲基、甲氧基和氨基取代的苯酚的计算已经得到了可靠的气相O−H键离解能，BDE（ArO−H）气体。苯酚，ArOH，和芳氧基自由基，ArO，的几何形状进行了优化，在（半经验）AM 1水平，然后通过单点密度泛函理论（DFT）计算，使用6- 31 G基组补充p-功能的氢原子和B3 LYP密度泛函。这得到BDE（PhO-H）气体= 86.46 kcal/mol，与实验值87.3 ± 1.5 kcal/mol非常吻合。除了一种化合物和构象外，所有的化合物和构象都具有比苯酚弱的O-H BDE，除了O-H基团指向这个取代基的邻甲氧基苯酚（BDE = 87.8 kcal/mol）。在可以进行比较的情况下，计算出的O−H BDE的差异与实验非常吻合（优于1 kcal/mol）。一个简单的基团加和方案也给出了很好的协议计算BDE（ArO−H）.
Calculations on phenol and a large number of phenols substituted with methyl, methoxyl, and amino groups have yielded reliable gas-phase O−H bond dissociation energies, BDE(ArO−H)gas. Geometries for the phenol, ArOH, and aryloxyl radical, ArO, were optimized at the (semiempirical) AM1 level followed by single point density functional theory (DFT) calculations using a 6-31G basis set supplemented with p-functions on the hydrogen atom and the B3LYP density functional. This gave BDE(PhO−H)gas = 86.46 kcal/mol, which is in good agreement with the experimental value of 87.3 ± 1.5 kcal/mol. All but one of the compounds and conformations examined had weaker O−H BDE's than phenol, the exception being o-methoxyphenol with the O−H group pointing toward this substituent (BDE = 87.8 kcal/mol). Where comparison was possible, calculated differences in O−H BDE's were in excellent agreement with experiment (better than 1 kcal/mol). A simple group additivity scheme also gave excellent agreement with calculated BDE (ArO−H)...