Adjacent lone pair (ALP) effects in heteroaromatic systems. 2. Isotope exchange of ring hydrogens in nitro- and fluoroimidazoles was written by Takeuchi, Yoshio;Kirk, Kenneth L.;Cohen, Louis A.. And the article was included in Journal of Organic Chemistry in 1978.Recommanded Product: 3034-41-1 This article mentions the following:
The ring protons of nitro- and fluoroimidazoles (and their N-Me derivatives) undergo base-catalyzed exchange in D2O by a combination of carbanion (C) and ylide (Y) pathways, which involve proton abstraction from the neutral imidazole species and from the imidazolium ion, resp. In 4-substituted imidazoles, C exchange occurs more readily at C-5 than at C-2, log kC correlating with 蟽o掳 for the NH- and with 蟽p掳 for the N-Me series. For 1-methyl-4-nitroimidazole, t1/2 = 2 min at C-5 (50掳, 0.2 N NaOD). In 1-methyl-5-X-imidazoles, exchange at C-4 occurs only via the Y pathway, carbanion formation in the neutral species being retarded by the adjacent lone pair (ALP) effect at N-3. The same effect is seen in the lack of C exchange at C-4 in 1-methylimidazoles. The ALP effect is considerably weaker or nonexistent at C-2. Most exchanges across the ring show correlations of log k with 蟼m掳. 4-Alkylimidazoles (but not 1,4-dialkylimidazoles) show enhanced C exchange at C-5, which may result from the existence of a trace concentration of the ketimine tautomer. Enhanced exchange at C-5 in 2-fluorohistidine is ascribed to a combination of the ketimine effect, C exchange involving catalysis by OH and intramol. general-base catalysis by the side-chain primary-amine function. The use of buffer catalysis for the T labeling of poorly reactive imidazoles is described. In the experiment, the researchers used many compounds, for example, 1-Methyl-4-nitroimidazole (cas: 3034-41-1Recommanded Product: 3034-41-1).
1-Methyl-4-nitroimidazole (cas: 3034-41-1) belongs to imidazole derivatives. Imidazole is the basic core of some natural products such as histidine, purine, histamine and DNA based structures, etc. Among the different heterocyclic compounds, imidazole is better known due to its broad range of chemical and biological properties. Imidazole is incorporated into many important biological compounds. The most pervasive is the amino acid histidine, which has an imidazole side-chain. Histidine is present in many proteins and enzymes, e.g. by binding metal cofactors, as seen in hemoglobin.Recommanded Product: 3034-41-1
Referemce:
Imidazole – Wikipedia,
Imidazole | C3H4N2 – PubChem