Proton and carbon-13 nuclear magnetic resonance studies of substituted pyrimidines. Part 3. Hindered internal rotation in some 4-(NN-dimethylamino)pyrimidines
- 1 January 1979
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 9,p. 1248-1252
- https://doi.org/10.1039/p29790001248
Abstract
The free energy of activation for internal rotation about the C–N exocyclic bond of some substituted 4-(NN-di-methylamino)pyrimidines has been determined using 1H and 13C n.m.r. line-shape analysis. Substituent effects on the rotational barrier of the dimethylamino group are evaluated. The influence of the position of the dimethyl-amino group with respect to the nitrogen atoms is discussed, the rotational barrier being higher in the 4- than in the 2-position. An interesting linear correlation between free energies of activation and 1J(C,H) coupling constants for the 4-dimethylamino group has been found.Keywords
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