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- Title
Structural peculiarities of configurational isomers of 1-styrylpyrroles according to <sup>1</sup>Н, <sup>13</sup>С and <sup>15</sup>N NMR spectroscopy and density functional theory calculations: electronic and steric hindrance for planar structure
- Authors
Afonin, Andrei V.; Ushakov, Igor A.; Pavlov, Dmitry V.; Schmidt, Elena Yu.; Dvorko, Marina Yu.
- Abstract
Comparative analysis of the 1Н and 13С NMR data for a series of the E and Z-1-styrylpyrroles, E and Z-1-(1-propenyl)pyrroles, 1-vinylpyrroles and styrene suggests that the conjugation between the unsaturated fragments in the former compounds is reduced. This is the result of the mutual influence of the donor p-π and π-π conjugation having opposite directions. According to the NMR data combined with the density functional theory calculations, the Z isomer of 1-styrylpyrrole has essentially a nonplanar structure because of the steric hindrance. However, the E isomer of 1-styrylpyrrole is also an out-of-plane structure despite the absence of a sterical barrier for the planar one. Deviation of the E isomer from the planar structure seems to be caused by an electronic hindrance produced by a mutual influence of the p-π and π-π conjugation. The structure of the E isomer of the 2-substituted 1-styrylpyrroles is similar to that of the 2-substituted 1-vinylpyrroles. The steric effects in the Z isomer of the 2-substituted 1-styrylpyrroles result in the large increase of the dihedral angle between planes of the pyrrole ring and double bond. Copyright © 2013 John Wiley & Sons, Ltd.
- Publication
Magnetic Resonance in Chemistry, 2013, Vol 51, Issue 6, p339
- ISSN
0749-1581
- Publication type
Article
- DOI
10.1002/mrc.3951