Theoretical study on the flash vacuum gas-phase pyrolysis reaction mechanism of 2-(2-benzylidenehydrazinyl)pyridine and analogous

• Published in: Computational and theoretical chemistry 2021-08, Vol.1202, p.113297, Article 113297
• Main Authors: Cuesta, Sebastián A, Márquez, Edgar A., Loroño, Marcos A., Paz, J.L., Mora, José R.
• Format: Article
• Language: English
• Subjects: B3LYP-D3; Hammet σp; Hydrazines; IBSI; Pyrolysis; Reaction mechanism
• ISSN: 2210-271X
• DOI: 10.1016/j.comptc.2021.113297

[Display omitted] •The pyrolysis of 2-[-2-benzylidenehydrazinyl]pyridine is affected by substituents.•The reaction order OCH3 > CH3 > H > Cl > NO2 is explained by the electronic effects.•The calculated energy values are in good agreement with the experimental one.•The empirical Hammett parameter values can be correlated with the reaction order. In the present study, the most favourable reaction mechanism in the flash vacuum pyrolysis of 2-[(2E)-2-benzylidenehydrazinyl]pyridine and analogous was theoretically studied using B3LYP-D3/6-311G(d,p) level. The influence of different substituents on the phenyl ring in the para position is evaluated at 500 K. A deep analysis of the mechanisms reveals the influence of the substituents in the activation energy, where the reactivity order OCH3 > CH3 > H > Cl > NO2 is found, following Hammet parameters (σp). To reach the transition state, geometric changes contribute more than 70% of the energy in agreement with the reaction force analysis. A recent independent gradient model (IGM) is also applied to establish an influence between the substituent and the strength of the bonds involved in the mechanism, through an intrinsic bond strength index (IBSI). Furthermore, the influence of the substituent was also evaluated in terms of interatomic distances and evolution percentages, finding high correlations with Hammet σp values.