Adjacent lone pair (ALP) effects in heteroaromatic systems. 1. Isotope exchange of ring hydrogens in alkylimidazoles was written by Takeuchi, Yoshio;Yeh, Herman J. C.;Kirk, Kenneth L.;Cohen, Louis A.. And the article was included in Journal of Organic Chemistry in 1978.Related Products of 3034-41-1 This article mentions the following:
Solvent D isotope exchange (D2O, 50°) is readily observed above pD 5 at C-2 in imidazole and its C– or N-alkyl derivatives The intermediate is an ylide, formed by base-catalyzed abstraction of H-2 from the imidazolium ion (path Y-2). A similar, but much slower, exchange is observed at C-4 (Y-4) or at C-5 (Y-5) at 100°. In strongly alk. media, NH imidazoles exchange more rapidly at C-4 or C-5 via a carbanion pathway (C) involving C-proton abstraction from the neutral mol.; in N-alkylimidazoles, however, only H-5 exchanges via the C pathway (C-5). The resistance to carbanion formation at C-4 is ascribed to the adjacent lone pair (ALP) effect, a significant electrostatic repulsion between lone pairs in the coplanar, sp2 orbitals at N-3 and C-4. The partial contributions of the ylide and carbanion pathways are evaluated from kinetic data at pD 10-11 and in 1 N NaOD, resp. For 1-methylimidazole (1 N NaOD, 100°C), C-5 exchange occurs 15 times faster than Y-5 and 3 times faster than Y-4. NMR signals for H-4 and H-5 are assigned on the basis of (1) spin-decoupling experiments, (2) nuclear Overhauser enhancements, (3) chem. transformations of 1-methylimidazole-d2, and (4) Δδ values. Ring protons adjacent to N-Me can be differentiated from other ring protons by a characteristic shift in δ with variation of solvent (Δδ); furthermore, relative to H-4, H-5 appears at higher field in nonpolar solvents and lower field in polar ones. In the experiment, the researchers used many compounds, for example, 1-Methyl-4-nitroimidazole (cas: 3034-41-1Related Products of 3034-41-1).
1-Methyl-4-nitroimidazole (cas: 3034-41-1) belongs to imidazole derivatives. The solubility of imidazoles in ethers is lower than that in alcohols and decreases with increasing chain length of the ethers . In contrast, the solubility of benzimidazoles in alcohols (C3–C6) is higher than in water and generally decreases with a This ring system is present in important biological building blocks, such as histidine and the related hormone histamine.Related Products of 3034-41-1
Referemce:
Imidazole – Wikipedia,
Imidazole | C3H4N2 – PubChem