The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Activated nucleophilic substitution of aromatic compounds. VI. Ortho-para relation. Reactivity of 2- and 4-chloropyridines, chloropyridine oxides, and chloronitrobenzenes with piperidine in methanol》. Authors are Coppens, G.; Declerck, F.; Gillet, C.; Nasielski, J..The article about the compound:2-Chloropyridine 1-oxidecas:2402-95-1,SMILESS:ClC1=CC=CC=[N+]1[O-]).Quality Control of 2-Chloropyridine 1-oxide. Through the article, more information about this compound (cas:2402-95-1) is conveyed.
cf. CA 57, 5881a. The effect of the groups NO2, cyclic, aromatic -N=, and N → O on the reactivity of the halogens of the chloronitrobenzenes, chloropyridines, and chloropyridine oxides with piperidine in methanol was studied. The reactivity sequence is N → O > NO2 -N=. The results are (compound, temperature, concentration of the halogen derivative, and second order constant in mole-1 sec.-1 = 107 given): 2-chloronitrobenzene (I), 80°, 0.00998, 144; I, 90°, 0.00985, 274; I, 100°, 0.00972, 537; I, 110°, 0.00959, 1090; 4-chloronitrobenzene (II), 70°, 0.00942, 28.8; II, 70°, 0.00942, 27.4; II, 80°, 0.0263, 61.4; II, 90°, 0.0259, 116; II, 90°, 0.0259, 122; II, 100°, 0.0256, 31; II, 110°, 0.0252, 442; 2-chloropyridine (III), 90°, 0.0482, 3.66; III, 100°, 0.0476, 8.60; III, 110°, 0.0469, 20.3; III, 120°, 0.0463, 40.7; 4-chloropyridine (IV), 70°, 0.0891, 8.37; IV, 80°, 0.0879, 16.4; IV, 90°, 0.0868, 32.3; IV, 100°, 0.0857, 67.2. Because of the low reactivity of the meta derivatives, a 50:50 piperidine-H2O mixture was used. These facts are in accordance with the hypothesis of internal solvation as the ex-planation of the high reactivity of the halogen in the meta position in 2,4-dinitrochlorobenzene with piperidine.
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Reference:
Isoxazole – Wikipedia,
Isoxazole | C3H3NO – PubChem