Publications by authors named "Dora G de Kowalewski"
The well-known N lone-pair orientation effect on (1)JCC spin-spin coupling constants (SSCCs) in oximes and their derivatives was used to study how negative hyperconjugative interactions of type LP1(O) → σ*CC depend on ortho interactions involving the OH group. This study demanded the following analyses: (i) a qualitative estimation of how (1)JCC SSCCs are affected by hyperconjugative interactions, (ii) a study of similar stereochemical effects to those in oximes, but in (1)JC1C2 and (1)JC1C6in a series of 2-substituted phenols, and (iii) a quantitative estimation, with the natural bond order approach, of some key electron delocalization interactions. A few unexpected results are quoted.
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- The study examines one- to three-bond 13C, 13C scalar couplings in pyrimidine derivatives using both experimental data and DFT calculations, focusing on four key contributions.
- It discusses the significance of non-contact terms and how substituent effects in pyrimidines compare to those in benzene and pyridine, with a dominance of the Fermi contact term in overall trends.
- Furthermore, while the inductive effect primarily influences 1J(C,C) couplings in benzene derivatives, this research highlights unique differences in pyrimidines, suggesting that nitrogen lone pair orientation can modify the impact of substituents on these couplings.