Étude de la tautomérie du benzotriazole à partir des mesures des moments dipolaires

Mauret, P.; Fayet, Jean-Pierre; Fabre, Martine; Elguero, José; Mendoza, Javier de

doi:10.1051/jcp/1974710115

Cited by 14 publications

(7 citation statements)

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“…15 They ascribed both instances of tautomerism to a double proton transfer in the complexes. In the present author's opinion, however, there is the scarcely explored possibility that the solvent dipolarity might enable indazole tautomerism since 1-methylindazole possesses a dipole moment of 1.5 D, 16 whereas 2-methylindazole has one of 3.4 D, 16 and is therefore considerably more polar.…”

Section: Methodsmentioning

confidence: 76%

“…As noted in the Introduction, the tautomerization of indazole from its less polar form (1H, µ 1meindazole = 1.5 D 16 to its more polar form (2H, µ 2meindazole = 3.4 D 16 ) can be facilitated by increasing the polarity of the solvent. As can be seen from Figure 5, neither the segment corresponding to the presence of the monomer (293-153 K) nor that corresponding to the doubly hydrogen bonded dimer suggest that raising the polarity of the medium leads to tautomerization from the 1H form to the 2H form in the ground electronic state.…”

Section: On the Tautomerization Of Indazolementioning

confidence: 96%

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On the solvatochromism, dimerization and tautomerism of indazole

Catalán¹

2013

Arkivoc

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A careful study of the solvatochromism of indazole was for the first time conducted in this work. The study revealed that indazole solvatochromism is governed mainly by the polarizability of the medium and, to a lesser extent, by its acidity and basicity. Based on the results of the solvatochromic analysis and their processing with Abe's model, this polar compound undergoes no significant change in dipole moment from its ground electronic state to its first excited state, which contradicts the predictions of other authors. Indazole dimerizes in both 2-methylbutane and 1-chlorobutane. However, neither its monomer nor its dimer undergoes tautomerization to 2H-indazole in the ground state in response to an increase in dipolarity of the medium. Also, based on experimental evidence, no tautomerization occurs in the first excited singlet or triplet of the compound.

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Section: Methodsmentioning

confidence: 76%

Section: On the Tautomerization Of Indazolementioning

confidence: 96%

On the solvatochromism, dimerization and tautomerism of indazole

Catalán¹

2013

Arkivoc

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“…Similarly, the N2 resonance of 6 at 306.5 ppm exhibits a 51-ppm downfield shift relative to the N3 resonance of 4 at 255.9 ppm. Thus, for 1-methyl-IH-1,2,3-triazole (11), the resole) G. C. Levy and R. L. Lichter, "Nitrogen-15 Nuclear Magnetic Resonance Spectroscopy", Wiley, New York, 1979, p 8. nance at 235.2 ppm is assigned to the iV-methyl nitrogen, a pyrrole-type N. The pyridine-type nitrogen atoms of 11, N2 and N3, are assigned to the resonances at 363.9 and 349.5 ppm, respectively. The N2 resonance is at lower field than the N3 resonance as a result of two neighboring nitrogen atoms for N2 but only one neighbor for N3.…”

Section: Resultsmentioning

confidence: 99%

Nitrogen-15 NMR spectroscopy: prototropic tautomerism of azoles

Wofford¹,

Forkey²,

Russell³

1982

J. Org. Chem.

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9-[l-(Methylthio)ethylidene]bicyclo[4.2.1]nonane (41).This compound is prepared and isolated as described for 15; yield 68%. Extremely pure product was obtained with the aid of high-performance LC (hexane): MS, m/e 196; 1H NMR (CDC13) 3.30 (m, 1), 3.03 (m, 1), 2.20 (s, 3), 1.97 (s, 3), 2.0-1.2 (m, 12). syn -9-Acetyl-9-chlorobicyclo[4.2.1]nona-2,4,7-triene (44). To a solution of vinyl ether 13 in S02 at -78 °C was added an excess (3 equiv) of S02C1F. The reaction was instantaneous. The reaction mixture was poured onto saturated aqueous NaHC03 and extracted into Et20. After the extract was dried (MgS04) and concentrated, hydrolysis of the intermediate ester was effected by passing the reaction mixture through a column of Si02 (CHC13 as eluent): NMR (CDC13) 6.0-5.7 (m, 4), 5.30 (d, 2), 3.53 (d, 2), 2.27 (s, 3); MS, m/e 194, 196. Carbocation Generation. NMR samples were prepared by condensing S02 from a gas cylinder into an NMR tube containing the substrate and cooled in a dry ice/acetone bath. The concentration of the samples was about 100-200 mg/0.3 mL of solvent. To the cooled solution, was carefully added freshly prepared HFS03/SbF5 (5:1) via the wall of the tube. In the case of the unsaturated substrates 13, 15, and 19,1 equiv of acid was used; the cations 47a-c were generated with a twofold excess of acid. Mixing was effected by shaking the samples vigorously with the aid of a vibromixer. Samples were checked with 60-MHz NMR spectroscopy. Spectroscopic investigations were performed in the temperature range of -100 to -30 °C. Quenching was effected by pouring the samples onto saturated aqueous NaHC03. AppendixTables IV and V contain collections of various and 13C NMR spectral data, respectively.

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“…As shown in the reaction scheme ( Fig. 1), benzotriazole exists in two tautomeric forms A and B. Spectroscopic data (UV, IR and 1 H NMR) (Negri & Caminati, 1996;Nesmeyanov et al, 1969;Poznań ski et al, 2007) and dipole moment measurements (Mauret et al, 1974) revealed that the 1H-tautomer A is the predominant species at room temperature.…”

Section: Chemical Contextmentioning

confidence: 91%

“…2016, Smith (2008), Trofimenko (1993Trofimenko ( , 2004. For the tautomerism of benzotriazole, see Mauret et al (1974), Negri & Caminati (1996); Nesmeyanov et al (1969), Poznań ski et al (2007.…”

Section: Figurementioning

confidence: 99%