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A Theoretical Study on the Photochemical Isomerization of 2,6-Dimethylpyrazine

Maurizio D’Auria

Organics · pp. 95–101 · Published 12 May 2022

10.3390/org3020007

Abstract

DFT calculations on the photoisomerization of 2,6-dimethylpyrazine allowed us to confirm the role of benzvalene isomers in the isomerization of hexatomic heterocyclic compounds. 2,6-Dimethylpyrazine in the excited singlet states can be converted into the corresponding Dewar isomers. If the S2 state is populated, two Dewar isomers can be obtained, while the S1 state allows the formation of only one of the possible Dewar isomers. Both Dewar isomers can be converted into the benzvalene isomer, that is, the precursor of 4,5-dimethylpyrimidine, the reaction product. In fact, the benzvalene isomer can be obtained from the Dewar isomers in processes that occur without an activation energy, and it is the more stable benzvalene isomers that can be obtained from the Dewar isomers. CASSCF study indicates the presence of a conical intersection allowing the direct formation of the benzvalene isomer.

Isomerization Conical intersection Chemistry Photoisomerization Singlet state Cis–trans isomerism Photochemistry Excited state

References (22)

  1. 1 Horspool, W., and Lenci, F. (2004). Photoisomerization of some nitrogen-containing hetero-aromatic compounds. CRC Handbook of Organic Photochemistry and Photobiology, CRC Press. [2nd ed.]. [DOI]
  2. 2 Horspool, W., and Lenci, F. (2004). Photochemistry of N-oxides. CRC Handbook of Organic Photochemistry and Photobiology, CRC Press. [2nd ed.]. [DOI]
  3. 3 Horspool, W., and Lenci, F. (2004). A new look at pyridinium salt photochemistry. CRC Handbook of Organic Photochemistry and Photobiology, CRC Press. [2nd ed.]. [DOI]
  4. 4 Klán, P., and Wirz, J. (2009). Photochemistry of Organic Compounds, John Wiley & Sons Ltd. [DOI]
  5. 5 Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Scalmani, G., Barone, V., Mennucci, B., and Petersson, G.A. (2009). Gaussian 09, Revision A.1, Gaussian, Inc.
  6. 6 Parr, R.G., and Yang, W. (1989). Density Functional Theory of Atoms and Molecules, Oxford University Press.
  7. 7 Chong, 1995, Time-dependent density-functional response theory for molecules [DOI]
  8. 8 Casida, 1998, Molecular excitation energies to high-lying bound states from time-dependent density-functional response theory: Characterization and correction of the time-dependent local density approximation ionization threshold [DOI]
  9. 9 Becke, 1993, Molecular excitation energies to high-lying bound states from time-dependent density-functional response theory: Characterization and correction of the time-dependent local density approximation ionization threshold [DOI]
  10. 10 Hegarty, 1979, Application of unitary group-methods to configuration-interaction calculations [DOI]
  11. 11 Eade, 1981, Direct minimization in MC SCF theory—The Quasi-Newton method [DOI]
  12. 12 Schlegel, 1982, MC SCF gradient optimization of the H2CO → H2 + CO transition structure [DOI]
  13. 13 Bernardi, 1984, MCSCF gradient calculation of transition structures in organic reactions [DOI]
  14. 14 Frisch, 1992, An Evaluation of 3 Direct MC-SCF Procedures [DOI]
  15. 15 Yamamoto, 1996, A Direct Derivative MC-SCF Procedure [DOI]
  16. 16 Siegbahn, 1984, A new direct CI method for large CI expansions in a small orbital space [DOI]
  17. 17 Weinstein, 1990, The Unitary Group Approach to Electronic Structure Computations
  18. 18 Klene, 2000, Parallel implementation of the CI-vector evaluation in full CI/CAS-SCF [DOI]
  19. 19 Lahmani, 1967, Photoisomerization of pyrazine and of its methylderivatives [DOI]
  20. 20 Su, 2006, CASCSF Study on the photochemical transposition reactions of pyrazines [DOI]
  21. 21 2021, The photochemical isomerization of hexatomic heterocyclic compounds [DOI]
  22. 22 (2022, January 10). Available online: https://spectrabase.com/spectrum/JGriPcJDFzk.

Cited by 8

The photochemical isomerization in pyridazine-N-oxide derivatives

Maurizio D’Auria, Lucia Emanuele · Tetrahedron · 2024

The Photochemical Isomerization in Pyridazine-N-oxide Derivatives

Maurizio D’Auria, Lucia Emanuele · Preprints.org · 2024

The Binding Mechanism of 2,5-Dimethylpyrazine with Amyloid Fibrils Derived from Different Protein Sources

Wenbin Zha, Lu Lin, Xiuqing Wang (4489777) · ACS Food Science & Technology · 2026

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