Encontrados 14 documentos, a visualizar página 1 de 2
Tautomer Selective Photochemistry in 1-(Tetrazol-5-yl)ethanol
Ismael, A.; Cristiano, M. L. S.; Fausto, R.; Gómez-Zavaglia, A.A combined matrix isolation FTIR and theoretical DFT/B3LYP/6-311++G(d,p) study of the molecular structure and photochemistry of 1-(tetrazol-5-yl)ethanol [1-TE] was performed. The potential energy surface landscapes of the 1H and 2H tautomers of the compound were investigated and the theoretical results were used to help characterize the conformational mixture existing in equilibrium in the gas phase prior to de...
Thermally Induced Sigmatropic Isomerization of Pseudosaccharyl Allylic Ether
Gómez-Zavaglia, A.; Kaczor, A.; Almeida, R.; Cristiano, M. L. S.; Eusébio, M. E. S.; Maria, T. M. R.; Mobili, P.; Fausto, R.The thermally induced sigmatropic isomerization of the pseudosaccharyl allylic ether [3-(allyloxy)-1,2-benzisothiazole 1,1-dioxide; ABID] has been investigated by a multidisciplinary approach using temperature dependent infrared spectroscopy, differential scanning calorimetry, and polarized light thermomicroscopy, complemented by theoretical methods. Migration of the allylic system from O to N occurs in the mel...
Matrix-isolation FTIR, theoretical structural analysis and reactivity of amino-...
Almeida, R.; Gómez-Zavaglia, A.; Kaczor, A.; Ismael, A.; Cristiano, M.L.S.; Fausto, R.In this work, two novel amino-substituted derivatives of saccharin, N-(1,1-dioxo-1,2-benzisothiazol-3-yl)-N-methyl amine (MBAD) and N-(1,1-dioxo-1,2-benzisothiazol-3-yl)-N,N-dimethyl amine (DMBAD), were synthesized and characterized, and their molecular structure and vibrational properties were investigated by matrix-isolation FTIR spectroscopy and theoretical calculations undertaken using different levels of a...
First observation of Chapman rearrangement of a pseudosaccharyl ether in the so...
Almeida, R.; Gómez-Zavaglia, A.; Kaczor, A.; Cristiano, M.L.S.; Eusébio, M.E.S.; Maria, T.M.R.; Fausto, R.3-(Methoxy)-1,2-benzisothiazole 1,1-dioxide, a pseudosaccharyl ether, was long ago known to undergo a thermal Chapman-like [1,3′]-isomerization to the corresponding N-methyl pseudosaccharin at temperatures above its melting point (ca. 184 °C) [Hettler H., Tetrahedron Lett.1968, 15, 1793]. In the present study, it is shown that this rearrangement can also take place in the solid state, at temperatures as low as ...
First observation of Chapman rearrangement of a pseudosaccharyl ether in the so...
Almeida, R.; Gómez-Zavaglia, Andrea; Kaczor, A.; Cristiano, M. L. S.; Eusébio, M. E. S.; Maria, T. M. R.; Fausto, R.3-(Methoxy)-1,2-benzisothiazole 1,1-dioxide, a pseudosaccharyl ether, was long ago known to undergo a thermal Chapman-like [1,3']-isomerization to the corresponding N-methyl pseudosaccharin at temperatures above its melting point (ca. 184 °C) [Hettler H., Tetrahedron Lett. 1968, 15, 1793]. In the present study, it is shown that this rearrangement can also take place in the solid state, at temperatures as low as...
Photochemistry of 5-allyloxy-tetrazoles: steady-state and laser flash photolysi...
Frija, L. M. T.; Khmelinskii, I. V.; Serpa, C.; Reva, I. D.; Fausto, R.; Cristiano, M. L. S.The photochemistry of three 5-allyloxy-tetrazoles, in methanol, acetonitrile and cyclohexane was studied by product analysis and laser flash photolysis. The exclusive primary photochemical process identified was molecular nitrogen elimination, with formation of 1,3-oxazines. These compounds were isolated in reasonable yields by column chromatography on silica gel and were fully characterized. DFT(B3LYP)/6-31G(d...
The Chapman-type rearrangement in pseudosaccharins: The case of 3-(methoxy)-1,2...
Kaczor, A.; Proniewicz, L.M.; Almeida, R.; Gómez-Zavaglia, A.; Cristiano, M.L.S.; Beja, A.M. Matos; Silva, M. Ramos; Fausto, R.The thermal Chapman-type rearrangement of the pseudosaccharin 3-(methoxy)-1,2-benzisothiazole 1,1-dioxide (MBID) into 2-methyl-1,2-benzisothiazol-3(2H)-one 1,1-dioxide (MBIOD) was investigated on the basis of computational models and knowledge of the structure of the reactant and product in the isolated and solid phases. X-ray diffraction was used to obtain the structure of the substrate in the crystalline phas...
Photochemistry and Vibrational Spectra of Matrix-Isolated 5-Ethoxy-1-Phenyl-1H-...
Frija, Luís M. T.; Reva, I. D.; Gómez-Zavaglia, A.; Cristiano, M. L. S.; Fausto, R.A combined matrix isolation FT-IR and theoretical DFT(B3LYP)/6-311++G(d,p) study of the molecular structure and photochemistry of 5-ethoxy-1-phenyl-1H-tetrazole (5EPT) was performed. A new method of synthesis of the compound is described. Calculations show three minima, very close in energy and separated by low-energy barriers (less than 4 kJ mol-1), in the ground-state potential energy profile of the molecule....
UV-induced photochemistry of matrix-isolated 1-phenyl-4-allyl-tetrazolone
Frija, L. M. T.; Reva, I. D.; Gómez-Zavaglia, A.; Cristiano, M. L. S.; Fausto, R.The photochemistry and molecular structure of 1-phenyl-4-allyl-tetrazolone (PAT) was studied by FT-IR matrix isolation spectroscopy and DFT(B3LYP)/6-311++G(d,p) calculations. The spectrum of matrix-isolated PAT monomers agrees well with the sum spectrum of three conformers predicted theoretically. UV irradiation (λ > 235 nm) of matrix-isolated PAT induces three types of photofragmentation: (1) production of phe...
Photochemistry of 1-phenyl-tetrazolone isolated in solid argon
Gómez-Zavaglia, A.; Reva, I.D.; Frija, L.; Cristiano, M.L.; Fausto, R.The molecular structure, vibrational spectra, tautomerism and photochemistry of the derivative of tetrazole, 1-phenyl-tetrazolone (C7H6N4O; PT) have been studied by FT-IR matrix isolation spectroscopy and DFT/B3LYP/6-311++G(d,p) calculations. Among the five structures in which PT could be expected to exist (two keto tautomers, one mesoionic olate-form and two different conformers of the hydroxyl tautomer), only...
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