Differentiation of substituent effects from hydrogen bonding and protonation effects in carbon-13 NMR spectra of pyridine N-oxides was written by Szafran, Miroslaw;Brycki, Bogumil;Dega-Szafran, Zofia;Nowak-Wydra, Barbara. And the article was included in Journal of the Chemical Society, Perkin Transactions 2: Physical Organic Chemistry (1972-1999) in 1991.Application of 3718-65-8 This article mentions the following:
Aromatic 13C chem. shifts are reported by 4- and 3-substituted pyridine N-oxides in deuteriochloroform, deuterium oxide, perchloric acid (60% in D2O) and dichloroacetic acid (80% in CDCl3), and also for O-alkylated derivatives in (CD3)2SO and D2O. The substituent chem. shift data show systematic nonadditivity in comparison with monosubstituted benzenes. Data for the position equation. For this position multiple substituent interactions are responsible for the nonadditive shifts; interactions have both an inductive (polar) and a resonance component. Hydrogen bonding and protonation effectes were differentiated from the substituent effect. The relative 13C chem.-shift difference [CΔ3 – Δ4)/Δ3] is a measure of the hydrogen bond and protonation effects and is not subject to substituent effects. 3-(Dimethylamino)pyridine N-oxide is protonated at the dimethylamino group, 4-(dimethylamino)pyridine N-oxide at the oxygen. In the experiment, the researchers used many compounds, for example, 3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8Application of 3718-65-8).
3,5-Dimethylpyridine 1-oxide (cas: 3718-65-8) belongs to pyridine derivatives. In contrast to benzene, Pyridine’s electron density is not evenly distributed over the ring, reflecting the negative inductive effect of the nitrogen atom. Halopyridines are particularly attractive synthetic building blocks in a variety of cross-coupling methods, including the Suzuki-Miyaura cross-coupling reaction.Application of 3718-65-8