A Theoretical Study on C-COOH Homolytic Bond Dissociation Enthalpies
A Theoretical Study on C-COOH Homolytic Bond Dissociation Enthalpies
复制标题
C-COOH均裂键解离焓的理论研究
DOI：
10.1021/jp910498y
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发表时间：
2010-06-03
影响因子：
2.9
通讯作者：
Li, Run
中科院分区：
文献类型：
--
作者：
Shi, Jing;Huang, Xiong-Yi;Li, Run
了解C-COOH均解键解离能(BDEs)对于理解涉及脱羧基反应的各种化学和生化过程是非常重要的。在本研究中，密度泛函理论(DFT方法)B3P86/6-311++G(2df，2p)//B3LYP/6-31+G(D)被发现能够可靠地预测各种结构无关的羧酸的C-COOHBDE。此优化方法的平均绝对偏差(MAD)和均方根偏差(RMSD)分别为2.0千卡/摩尔和2.5千卡/摩尔。有了授权的理论方案，一个包含100多个羧酸的广泛的C-COOHBDE标度已经建立，这一数据的可用性使得详细研究了四种类型的羧酸的远程取代基效应，包括对取代苯甲酸、β-取代顺丙烯酸、β-取代反式丙烯酸和取代丙酸。用本文获得的C-COOHBDE数据，还发现了羧酸的C-COOHBDE与其烃类类似物的C-HBDE之间存在良好的线性关系。通过比较Pd催化脱羧化反应的能垒(Delta G(脱羧基)(双匕首))和相应的C-COOHBDE，发现Delta G(脱羧基)(双匕首)与C-CoolBDE呈负相关。
The knowledge of C-COOH homolytic bond dissociation enthalpies (BDEs) is of great importance in understanding various chemical and biochemical processes involving the decarboxylation reaction. In the present study, the density functional theory (DFT method), B3P86/6-311++G(2df,2p)//B3LYP/6-31+G(d), is found to be reliable to predict the C-COOH BDE of various structurally unrelated carboxylic acids. The mean absolute deviation (MAD) and root-mean-square deviation (rmsd) of this optimal method are equal to 2.0 and 2.5 kcal/mol, respectively. With the authorized theoretical protocol in hand, an extensive C-COOH BDE scale containing over 100 carboxylic acids has been established, The availability of this body of data enabled a detailed investigation of remote substituent effect on four types of carboxylic acids, including para-substituted benzoic acid, beta-substituted cis-propenoic acid, beta-substituted trans-propenoic acid, and substituted propiolic acid. Also with the C-COOH BDE data obtained in this work, an excellent linear relationship has been found between the C-COOH BDE of carboxylic acids and the C-H BDE of their hydrocarbon analogues. After comparing the energy barrier of the Pd-catalyzed decarboxylation reaction (Delta G(decarboxylation)(double dagger)) with the related C-COOH BDE, a negative correlation between the Delta G(decarboxylation)(double dagger) and the C-COOL BDE was found.