Theoretical Study of Substituent Effects on Bond Dissociation Enthalpies in Lignite Model Compounds

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	Theoretical Study of Substituent Effects on Bond Dissociation Enthalpies in Lignite Model Compounds
	Wang Xinhua ; Feng Li ; Cao Zexing ; Liu Xiangchun ; Tang Haiyan ; Zhang Man ; Cao ZX(曹泽星)
刊名	http://dx.doi.org/10.6023/A13030318
	2013
关键词	DENSITY-FUNCTIONAL THEORY PHENETHYL PHENYL ETHERS LOW-RANK COAL AB-INITIO ENERGIES THERMOCHEMISTRY PYROLYSIS LINKAGES KINETICS
英文摘要	National Basic Research Program of China [2012CB214901]; National Natural Science Foundation of China [51274197]; Lignite is an abundant natural resource that is a potential source of clean fuel and value-added chemicals. The mechanisms by which thermal and catalytic treatments deconstruct lignite remain elusive, which is where quantum mechanical calculations can offer fundamental insights. In order to investigate the cleavage of C-O bridge bond, which is the critical step in the thermal decomposition of lignite, the alpha-O-4 and beta-O-4 types of structural units are selected as lignite model compounds to calculate the C-O bond dissociation enthalpies using several kinds of density functional theory methods (B3PW91, B3P86, PBE1PBE, BMK, M06-2X and M05-2X) at 6-31+G(d,p) level. By the comparison between the results and the theoretical benchmark values provided by CBS-QB3 method, M05-2X functional was applied for the calculations on C-O bond dissociation enthalpies. The present results indicate that the C-O average bond dissociation enthalpies are 51.0 kcal/mol and 66.1 kcal/mol for the alpha-O-4 and beta-O-4 types of model compounds, respectively. Local substituents have a great effect on the C-O bond dissociation enthalpies, the C-O bond dissociation enthalpies will decrease when the adjacent arene rings are substituted by electron donating groups (OH, OCH3 and CH3), while the results are opposite for the electron withdrawing groups such as carboxyl group. Then the substituent effects are deeply analyzed on the basis of the ground-state effect and radical effect. An electron donating group can stabilize the phenoxy radicals (radical effect), however, an electron withdrawing group has the opposite effect. In most cases, the radical effect is more important than the ground-state effect. Furthermore, there is a negligible correlation between the C-O bond distances and strengths, and the C-O bond dissociation enthalpies cannot be predicted so easily. Interestingly, the C-O bond dissociation enthalpies can be significantly influenced by the intramolecular hydrogen bond, if the intramolecular hydrogen bond still exists after the cleavage of the C-O bond, the bond dissociation enthalpies will be lower.
语种	英语
出版者	SCIENCE PRESS
内容类型	期刊论文
源URL	[http://dspace.xmu.edu.cn/handle/2288/88970]
专题	化学化工－已发表论文
推荐引用方式 GB/T 7714	Wang Xinhua,Feng Li,Cao Zexing,et al. Theoretical Study of Substituent Effects on Bond Dissociation Enthalpies in Lignite Model Compounds[J]. http://dx.doi.org/10.6023/A13030318,2013.
APA	Wang Xinhua.,Feng Li.,Cao Zexing.,Liu Xiangchun.,Tang Haiyan.,...&曹泽星.(2013).Theoretical Study of Substituent Effects on Bond Dissociation Enthalpies in Lignite Model Compounds.http://dx.doi.org/10.6023/A13030318.
MLA	Wang Xinhua,et al."Theoretical Study of Substituent Effects on Bond Dissociation Enthalpies in Lignite Model Compounds".http://dx.doi.org/10.6023/A13030318 (2013).