Theoretical Studies on Energetic Property and Stability of Pyrazine and Pyridine Derivatives

• Published in: Chinese journal of chemistry 2010-12, Vol.28 (12), p.2364-2370
• Main Authors: Fan, Xiaowei, Gu, Chenggang, Chen, Gong, Ju, Xuehai
• Format: Article
• Language: English
• Subjects: bond dissociation energy; density functional calculations; heats of formation; intramolecular hydrogen bond; pyrazine and pyridine compounds
• ISSN: 1001-604X; 1614-7065
• DOI: 10.1002/cjoc.201190005

Density functional calculations at the B3LYP level with 6‐311G** and aug‐cc‐pVDZ basis sets were performed to predict the heats of formation (HOFs) for two pyrazine derivatives and eight pyridine derivatives. In the isodesmic reactions designed for the computation of heats of formation (HOFs), pyrazine and pyridine were chosen as reference compounds. The N‐oxidations for the ring nitrogen of pyrazine and pyridine derivatives decrease the HOF values when N‐oxide oxygen is neighboring with amino groups, but increase when it neighbors with nitro groups. Thermal stability was evaluated via bond dissociation energies (BDE) at the UB3LYP/6‐311G** level. As a whole, the homolysis of C–NO2 bonds is the main step for bond dissociation of the title compounds. The BDE values of title compounds are influenced by intramolecular hydrogen bonds. The hydrogen bond effects associated with the length of the H···O bonds were analyzed by the electron density at the critical points and natural bond orbital. Density functional calculations at the B3LYP level in conjunction with 6‐311G** and aug‐cc‐pVDZ basis sets were performed to predict the heats of formation (HOFs) and bond dissociation energy of pyrazine and pyridine derivatives.