Origin of methyl torsional barrier in 1-methyl-2-(1H)-pyridone
DSpace at IIT Bombay
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Title |
Origin of methyl torsional barrier in 1-methyl-2-(1H)-pyridone
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Creator |
PRADHAN, B
SINGH, BP NANDI, CK CHAKRABORTY, T KUNDU, T |
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Subject |
pi(asterisk)-sigma(asterisk) hyperconjugation mechanism
internal-rotation barriers staggered conformation substituted toluenes anionic states ethane 2-pyridone s-1 |
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Description |
The laser induced fluorescence excitation and single vibronic excitation dispersed fluorescence spectra have been studied for supersonic jet cooled 1-methyl-2(1h)-pyridone. The methyl torsional bands and some low frequency vibrational transitions were assigned for both ground and excited states. The torsional parameters V-3=244 cm(-1) and V-6=15 cm(-1) for the ground state and V-3 = 164 cm(-1) and V-6= 40 cm(-1) for the excited state were obtained. To get the insight into the methyl torsional barrier, ab initio calculations were performed and compared with the experimental results. Origin of potential barrier was traced by partitioning the barrier energy into changes in bond antibond interaction, structural, and steric energies accompanying methyl rotation using natural bond orbital analysis. The role of local interactions in ascertaining the barrier potential reveals that its nature cannot be understood without considering the molecular flexing. The hyperconjugation between CH sigma* and ring pi* observed in lowest unoccupied molecular orbital (LUMO) stabilizes the methyl group conformer that undergoes a 60 degrees rotation in the excited state with respect to that of the ground state, and it is the change in LUMO that plays important role in the excited state barrier formation. (c) 2005
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Publisher |
AMER INST PHYSICS
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Date |
2011-07-16T10:56:54Z
2011-12-26T12:49:44Z 2011-12-27T05:35:22Z 2011-07-16T10:56:54Z 2011-12-26T12:49:44Z 2011-12-27T05:35:22Z 2005 |
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Type |
Article
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Identifier |
JOURNAL OF CHEMICAL PHYSICS, 122(20), -
0021-9606 http://dx.doi.org/10.1063/1.1901567 http://dspace.library.iitb.ac.in/xmlui/handle/10054/4410 http://hdl.handle.net/10054/4410 |
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Language |
en
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