1. Modulations in restricted amide rotation by steric induced conformational trapping
- Author
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Krishnan, V.V., Thompson, William B., Goto, Joy J., Maitra, Kalyani, and Maitra, Santanu
- Subjects
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MOLECULAR rotation , *AMIDES , *CONFORMATIONAL analysis , *CHEMICAL bonds , *MOLECULAR models , *METHYL groups - Abstract
Abstract: The rotation around the amide bond in N,N-diethyl-m-toluamide (m-DEET) has been studied extensively and often used in laboratory instructions to demonstrate the phenomenon of chemical exchange. Herein, we show that a simple modification to N,N-diethyl-o-toluamide (o-DEET) significantly alters the dynamics of the restricted rotation around the amide bond due to steric interactions between the ring methyl group and the two N-ethyl groups. This alters the classic two-site exchange due to restricted rotation around the amide bond, to a three-site exchange, with the third conformation trapped at a higher-energy state compared to the other two. This often overlooked phenomenon is elucidated using variable-temperature NMR, two-dimensional exchange spectroscopy and molecular modeling studies. [Copyright &y& Elsevier]
- Published
- 2012
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