# Computational Study of the Kinetics and Mechanisms of Gas-Phase Decomposition of N-Diacetamides Using Density Functional Theory

## TL;DR

This paper uses computational methods to study how N-diacetamides break down in the gas phase, focusing on how different chemical groups affect the reaction.

## Contribution

The study introduces a detailed computational mechanism for N-diacetamide decomposition with substituent effects and optimized DFT methods.

## Key findings

- A six-membered transition state was identified in the decomposition mechanism.
- Electron-withdrawing and donor groups significantly influence nitrogen lone-pair delocalization.
- Dispersion corrections and specific basis sets were crucial for accurate thermodynamic results.

## Abstract

In this research work, we examined the decomposition mechanisms of N-substituted diacetamides. We focused on the substituent effect on the nitrogen lone-pair electron delocalization, with electron-withdrawing and electron donor groups. DFT functionals used the following: B1LYP, B3PW91, CAMB3LYP, LC-BLYP, and X3LYP. Dispersion corrections (d3bj) with Becke–Johnson damping were applied when necessary to improve non-covalent interactions in the transition state. Pople basis sets with higher angular moments and def2-TZVP basis sets were also applied and were crucial for obtaining consistent thermodynamic parameters. The proposed mechanism involves a six-membered transition state with the extraction of an α hydrogen. Several conformers of N-diacetamides were used to account for the decrease in entropy in the transition state in the rate-determining state. All calculations, including natural bond orbital (NBO) analyses, were performed using the Gaussian16 computational package and its GaussView 6.0 visualizer, along with VMD and GNUPLOT software. The isosurfaces and IBSIs were calculated using MultiWFN and IGMPlot, respectively.