Initial mechanisms for the dissociation of carbon from electronically-excited nitrotoluene molecules

Bing Yuan; Hergen Eilers

doi:10.1063/1.5011773

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Initial mechanisms for the dissociation of carbon from electronically-excited nitrotoluene molecules

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Initial mechanisms for the dissociation of carbon from electronically-excited nitrotoluene molecules

Bing Yuan and Hergen Eilers

AIP advances, Vol.7(12), pp.125120-125120-22

12/01/2017

DOI: https://doi.org/10.1063/1.5011773

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Abstract

Materials Science, Multidisciplinary

Nanoscience & Nanotechnology

Physics, Applied

Science & Technology

Materials Science

Physical Sciences

Physics

We calculated the photoinduced decomposition of various nitrotoluene molecules, resulting in the formation of atomic carbon, at the B3LYP/6-311++G(d,p) level of theory using Gaussian 09. In addition, we used TD-DFT (B3LYP/6-311++G(d, p)) to calculate the excitation energies. The results confirm our previously reported experimental results. Specifically, we show that the absorption of 226 nm (5.49 eV) light can lead to the decomposition of nitrotoluene molecules and the formation of atomic carbon. One 226 nm photon is sufficient for the dissociation of carbon from 2-NT and 4-NT molecules. During the dissociation process, the CH3 group provides the dissociated carbon atom and the NO2 group accepts the H atoms from either the CH3 group or the benzene ring before carbon exits the molecular system. For the second and third carbon dissociation of 2-NT, the energy barriers are 6.70 eV and 7.43 eV, respectively, and two 226 nm photons would need to be absorbed by the molecule. If extra NO is present during the first carbon dissociation of 2-NT, it gets involved in the last two decomposition steps and forms a C=NH-N=O structure which stabilizes the decomposition products and lowers the energy barrier from 5.22 eV to 4.70 eV. However, for the second and third carbon dissociation of 2-NT, the NO molecules have no apparent effect. For nitrotoluene molecules with two or three NO2 groups (i.e., 2,4-DNT, 2,6-DNT, 3,4-DNT, and 2,4,6-TNT), the first carbon dissociation energies are between 5.26 eV and 5.57 eV. The carbon dissociation pathways for these molecules are similar to those of 2-NT. In 2,4-DNT, the lowest energy barriers for the second and third carbon dissociation are 6.54 eV and 6.60 eV, respectively, which are about 1 eV higher than the energy barrier for the first carbon dissociation. In case of 2,4-DNT/NO and 2,4,6-TNT/NO, NO acts as a catalyst in the first carbon dissociation processes and forms a C=NH-N=O structure which lowers the energy barriers by 0.48 eV and 0.89 eV, respectively. (c) 2017 Author(s).

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Title: Initial mechanisms for the dissociation of carbon from electronically-excited nitrotoluene molecules
Creators: Bing Yuan - Washington State University
Hergen Eilers - Washington State Univ, Inst Shock Phys, Appl Sci Lab, Spokane, WA 99202 USA
Publication Details: AIP advances, Vol.7(12), pp.125120-125120-22
Academic Unit: Institute for Shock Physics
Publisher: Amer Inst Physics
Number of pages: 22
Grant note: N000014-16-1-2088 / ONR; Office of Naval Research
Identifiers: 99900876937701842
Language: English
Resource Type: Journal article