Origin of methyl torsional barrier in 1-methyl-2(1H)-pyridinimine and 3-methy 1-2(1H)-pyridone: II. Ground state

B. Pradhan, Rajeev K. Sinha, Bhanu P. Singh, T. Kundu

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

To get the insight into the electronic structure-methyl torsion correlation in nitrogen heterocyclic molecules, a comparative study on torsion of the methyl group in 1-methyl-2(1H)pyridone (1MPY), 1-methyl-2(1H)pyridinimine (1MPI), and 3-methyl-2(1H)pyridone (3MPY) was carried out using ab initio calculations. To understand the barrier forming mechanism in the ground state and its consequence on the molecular structure, the ground state torsional potential has been investigated by partitioning the barrier energy using the natural bond orbital (NBO) theoretical framework. The NBO analysis reveals that the delocalization energy is the barrier forming term whereas the Lewis energy is always antibarrier for all these molecules. To get further insight into the effect of local electronic structure on the methyl torsional barrier, the individual bond-antibond interactions and structural energy contributions have been investigated. It was found that when the bond order difference between the vicinal bonds does not change appreciably during the course of methyl rotation, the local electronic interactions with the methyl group do not play any decisive role in barrier formation as observed in the case of 1MPY and 1MPI In these cases, it is the skeletal relaxation during methyl rotation that plays an important role in determining the barrier. On the other hand, if the bond order change is appreciable as is the case for 3MPY, the local interactions alone suffice to describe the origin of the torsional barrier of the methyl group.

Original languageEnglish
Article number114313
JournalJournal of Chemical Physics
Volume126
Issue number11
DOIs
Publication statusPublished - 08-04-2007

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Pyridones
Ground state
Torsional stress
Electronic structure
ground state
Molecules
Energy barriers
Molecular structure
Nitrogen
torsion
electronic structure
orbitals
energy
interactions
molecules
molecular structure
nitrogen
electronics

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

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title = "Origin of methyl torsional barrier in 1-methyl-2(1H)-pyridinimine and 3-methy 1-2(1H)-pyridone: II. Ground state",
abstract = "To get the insight into the electronic structure-methyl torsion correlation in nitrogen heterocyclic molecules, a comparative study on torsion of the methyl group in 1-methyl-2(1H)pyridone (1MPY), 1-methyl-2(1H)pyridinimine (1MPI), and 3-methyl-2(1H)pyridone (3MPY) was carried out using ab initio calculations. To understand the barrier forming mechanism in the ground state and its consequence on the molecular structure, the ground state torsional potential has been investigated by partitioning the barrier energy using the natural bond orbital (NBO) theoretical framework. The NBO analysis reveals that the delocalization energy is the barrier forming term whereas the Lewis energy is always antibarrier for all these molecules. To get further insight into the effect of local electronic structure on the methyl torsional barrier, the individual bond-antibond interactions and structural energy contributions have been investigated. It was found that when the bond order difference between the vicinal bonds does not change appreciably during the course of methyl rotation, the local electronic interactions with the methyl group do not play any decisive role in barrier formation as observed in the case of 1MPY and 1MPI In these cases, it is the skeletal relaxation during methyl rotation that plays an important role in determining the barrier. On the other hand, if the bond order change is appreciable as is the case for 3MPY, the local interactions alone suffice to describe the origin of the torsional barrier of the methyl group.",
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Origin of methyl torsional barrier in 1-methyl-2(1H)-pyridinimine and 3-methy 1-2(1H)-pyridone : II. Ground state. / Pradhan, B.; Sinha, Rajeev K.; Singh, Bhanu P.; Kundu, T.

In: Journal of Chemical Physics, Vol. 126, No. 11, 114313, 08.04.2007.

Research output: Contribution to journalArticle

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T1 - Origin of methyl torsional barrier in 1-methyl-2(1H)-pyridinimine and 3-methy 1-2(1H)-pyridone

T2 - II. Ground state

AU - Pradhan, B.

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AB - To get the insight into the electronic structure-methyl torsion correlation in nitrogen heterocyclic molecules, a comparative study on torsion of the methyl group in 1-methyl-2(1H)pyridone (1MPY), 1-methyl-2(1H)pyridinimine (1MPI), and 3-methyl-2(1H)pyridone (3MPY) was carried out using ab initio calculations. To understand the barrier forming mechanism in the ground state and its consequence on the molecular structure, the ground state torsional potential has been investigated by partitioning the barrier energy using the natural bond orbital (NBO) theoretical framework. The NBO analysis reveals that the delocalization energy is the barrier forming term whereas the Lewis energy is always antibarrier for all these molecules. To get further insight into the effect of local electronic structure on the methyl torsional barrier, the individual bond-antibond interactions and structural energy contributions have been investigated. It was found that when the bond order difference between the vicinal bonds does not change appreciably during the course of methyl rotation, the local electronic interactions with the methyl group do not play any decisive role in barrier formation as observed in the case of 1MPY and 1MPI In these cases, it is the skeletal relaxation during methyl rotation that plays an important role in determining the barrier. On the other hand, if the bond order change is appreciable as is the case for 3MPY, the local interactions alone suffice to describe the origin of the torsional barrier of the methyl group.

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