Ab inito study on the isomerization reaction of nitroguanidine

作者：Wang WN; Ren FD; Bi YL; Wang WL^*

来源：Chinese Journal of Chemical Physics, 2005, 18(5): 765-770.

• nitroguanidine
• conjugative effect
• H transfer
• isomerization reaction
• rate constant

Theoretical studies on the alpha- and beta-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 a-form nitroguanidine were different, the longest bond length was 1.430 angstrom, the shortest was 1.283 angstrom. But they were almost similar in beta-form, the longest was 1.375 angstrom, the shortest was 1.322 angstrom. Therefore there were conjugative effects in beta-forrn but not in alpha-form. The calculated results also show that the beta-form is stable with respect to the alpha-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 x 10-(11) s(-1) and the equilibrium constant was 1.00 x 10(5) at 298 K. With the temperature increasing, the equilibrium value decayed and the reaction process was more difficult.

• 出版日期2005-10
• 单位陕西师范大学