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Ab inito Study on the Isomerization Reaction of Nitroguanidine
Wang Weina,Ren Fude,Bi Yanli,Wang Wenliang*
Author NameAffiliationE-mail
Wang Weina School of Chemistry and Materials Science, Shanxi Normal University, Xi’an 710062  
Ren Fude School of Chemistry and Materials Science, Shanxi Normal University, Xi’an 710062  
Bi Yanli School of Chemistry and Materials Science, Shanxi Normal University, Xi’an 710062  
Wang Wenliang* School of Chemistry and Materials Science, Shanxi Normal University, Xi’an 710062 wlwang@snnu.edu.cn 
Abstract:
Theoretical studies on the α- and β-forms nitroguanidine were carried out using ab initio theoretical methods, at the MP2/6-31G(d,p) level. The predicted geometrical parameters were in good agreement with the available theoretical values, which calculated by other author. The three C-N bond lengths in α-form nitroguanidine were different, the longest bond length was 1.430 A, the shortest was 1.283 A. But they were almost similar in β-form, the longest was 1.375 A, the shortest was 1.322 A. Therefore there were conjugative effects in β-form but not in α-form. The calculated results also show that the β-form is stable with respect to the α-form from energetically, lower 28.16 kJ/mol corrected with zero point vibrational energy. The transition-state for the unimolecular isomerization was conformed by the IRC calculation. The calculated energy barrier for the direct intramolecular hydrogen atom transfer isomerization process was 132.95 kJ/mol. The isomerization reaction, exothermal reaction, is a typical intramolecular hydrogen atom synfacial transfer reaction. Rate constants of the isomerization reaction were evaluated within the temperature range of 200-1773 K by the classical transition state theory. The rate constant was 1.99×10-11 s-1 and the equilibrium constant was 1.00×105 at 298 K. With the temperature increasing, the equilibrium value decayed and the reaction process was more difficult.
Key words:  Nitroguanidine, Conjugative effect, H transfer, Isomerization reaction, Rate constant
FundProject:
硝基胍H迁移异构化反应动力学的从头计算研究
王渭娜,任福德,毕艳丽,王文亮*
摘要:
采用MP2/6-31G(d,p)从头计算方法优化获得硝基胍两种异构体及过渡态的几何结构,在相同水平上计算了各驻点频率,并进行了IRC分析.利用过渡态理论,计算了在200~1773 K的H迁移异构化反应的速率常数. 结果表明, β型硝基胍中形成大范围的离域大∏键,存在显著的共轭效应使其比α型稳定,能量比α型低28.16 kJ/mol;硝基胍由α型向β型H迁移异构化反应的活化能为132.95 kJ/mol. 298 K时速率常数为1.99×10-11 s-1,平衡常数为1.00×105;硝基胍的异构化是一个典型的同面H迁移放热反应,随温度升高,平衡常数逐渐减小,不利于α型通过H迁移向β型转化.
关键词:  硝基胍  共轭效应  H迁移  异构化反应  速率常数
DOI:10.1088/1674-0068/18/5/765-770
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