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Sigmatropic rearrangements in 5-allyloxytetrazoles
Frija, L.; Reva, I. D.; Ismael, A.; Coelho, Daniela; Fausto, R.; Cristiano, Maria Lurdes SantosMechanisms of thermal isomerization of allyl tetrazolyl ethers derived from the carbocyclic allylic alcohols cyclohex-2-enol and 3-methylcyclohex-2-enol and from the natural terpene alcohol nerol were investigated. In the process of the syntheses of the three 1-aryl-5-allyloxytetrazoles, their rapid isomerization to the corresponding 1-aryl-4-allyltetrazol-5-ones occurred. The experiments showed that the imidat...
Matrix Isolation FTIR Spectroscopic and Theoretical Study of 3,3-Dichloro-1,1,1...
Lucena Jr., J. R.; Sharma, A.; Reva, I. D.; Araújo, R. M. C. U.; Ventura, E.; Monte, S. A. do; Braga, C. F.; Ramos, M. N.; Fausto, R.The molecular structure and infrared spectrum of the atmospheric pollutant 3,3-dichloro-1,1,1-trifluoropropane (HCFC-243) were characterized experimentally and theoretically. The theoretical calculations show the existence of two conformers, with the gauche (G) and trans (T) orientation around the HCCC dihedral angle. Conformer G was calculated to be more stable than form T by more than 10 kJ mol−1. In consonan...
Matrix-Isolated Diglycolic Anhydride: Vibrational Spectra and Photochemical Rea...
Jarmelo, S.; Reva, I. D.; Lapinski, L.; Nowak, M. J.; Fausto, R.The structure of diglycolic anhydride (1,4-dioxane-2,6-dione; DGAn) isolated in a low-temperature argon matrix at 10 K was studied by means of FTIR spectroscopy. Interpretation of the experimental vibrational spectrum was assisted by theoretical calculations at the DFT(B3LYP)/aug-cc-pVTZ level. The optimized structure of the isolated DGAn molecule adopts an envelope conformation, which was found to resemble clo...
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...
Photochemistry of 5-allyloxy-tetrazoles: steady-state and laser flash photolysi...
Frija, L.; Khmelinskii, Igor; Serpa, C.; Reva, I. D.; Fausto, R.; Cristiano, Maria Lurdes SantosThe 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...
Matrix-Isolated Monomeric Tryptophan: Electrostatic Interactions as Nontrivial...
Kaczor, A.; Reva, I. D.; Proniewicz, L. M.; Fausto, R.An extensive analysis of the conformational space of tryptophan (Trp) was performed at the B3LYP/6-311++G(d,p) level and verified by comparison with the infrared spectra of the compound isolated in low-temperature argon and xenon matrixes. Different types of conformers have been unequivocally identified in the matrixes. Type I exhibits the trans arrangement of the carboxylic group and is stabilized by an O−H···...
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...
UV-induced photochemistry of matrix-isolated 1-phenyl-4-allyl-tetrazolone
Frija, L.; Reva, I. D.; Gómez-Zavaglia, A.; Cristiano, Maria Lurdes Santos; 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 (k > 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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