引用本文:
【打印本页】   【HTML】   【下载PDF全文】   View/Add Comment  【EndNote】   【RefMan】   【BibTex】
←前一篇|后一篇→ 过刊浏览    高级检索
本文已被:浏览 1112次   下载 1170 本文二维码信息
码上扫一扫!
分享到: 微信 更多
Ab inito Study on the Isomerization Reaction of Nitroguanidine
Wang Weina, Ren Fude, Bi Yanli, Wang Wenliang*
School of Chemistry and Materials Science, Shanxi Normal University, Xi’an 710062
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*
陕西师范大学化学与材料科学学院,西安,710062
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
分类号: