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FTIR spectroscopic and theoretical study of matrix-isolated (E)-1-(cyclopropyld...
Duarte, L.; Giuliano, B. M.; Reva, I.; Campos, Ana M. F. Oliveira; Fausto, R.Photochromic systems are important due to their industrial applications in variable optical transmission materials and optobioelectronic devices. For such applications, the organic photochromic compounds involved are usually incorporated in polymers, liquid crystalline materials, or other convenient host matrices [1, 2]. Herein, a photochromic compound, (E)-1-(cyclopropyldiazenyl)naphthalen-2-ol (show in Figure...
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...
Conformational Space and Photochemistry of α-Terpinene
Marzec, K. M.; Reva, I.; Fausto, R.; Malek, K.; Proniewicz, L. M.α-Terpinene is a natural product that is isolated from a variety of plant sources and is used in the pharmaceutical and perfume industries. In the atmosphere, under the influence of sunlight, α-terpinene undergoes a series of photochemical transformations and contributes to the formation of the secondary organic aerosols. In the present work, α-terpinene has been isolated in low-temperature xenon and argon matr...
Crystal and Molecular Structure of dl-Serine Hydrochloride Studied by X-Ray Dif...
Jarmelo, S.; Reva, I.; Rozenberg, M.; Silva, M. Ramos; Beja, A. M. Matos; Fausto, R.The structure of dl-serine·HCl was studied by three complementary techniques. Experimental Fourier transform infrared (FT-IR) spectra of pure NH/OH polycrystalline dl-serine·HCl [HO−CH2−CH(NH3+)−COOH·Cl−] and the respective deuterated derivatives [ND/ODAlcohol/Acid (<10% and ca. 60% D)] were recorded in the region 4000−400 cm−1 in the temperature range 300−10 K and interpreted. The assignments were confirmed by...
Molecular structure and vibrational spectra of 2(5H)-furanone and 2(5H)-thiophe...
Breda, S.; Reva, I.; Fausto, R.The structure and vibrational spectra of two five-membered heterocyclic [alpha]-carbonyl compounds have been studied. The experimental FTIR spectra 2(5H)-furanone and 2(5H)-thiophenone monomers isolated in inert argon matrices at 10 K are reported and discussed. The interpretation of the experimental data is supported by vibrational calculations at the MP2 and DFT(B3LYP) levels of theory with the 6-311++G(d,p) ...
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...
Low-Temperature FTIR Spectroscopic and Theoretical Study on an Energetic Nitroi...
Simões, P. N.; Reva, I.; Pedroso, L. M.; Fausto, R.; Portugal, A. A.This paper presents an overview of recent progress in spectroscopic studies of the energetic nitroimine 4,6-bis(nitroimino)-1,3,5-triazinan-2-one (DNAM), based on experimental and theoretical data. The following topics are considered: variable temperature FTIR spectroscopy (4000−400 cm-1) applied to the study of natural and isotopically substituted (deuterated) samples aiming to obtain a successful vibrational...
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...
UV-induced unimolecular photochemistry of 2(5H)-furanone and 2(5H)-thiophenone ...
Breda, S.; Reva, I.; Fausto, R.Monomers of two simplest five-membered heterocyclic α-carbonyl compounds, 2(5H)-furanone and 2(5H)-thiophenone were isolated in low temperature inert argon matrices and their UV-induced photochemistry was studied. The reaction photoproducts were identified by FTIR spectroscopy and interpretation of the experimental results was assisted by theoretical calculations of the infrared spectra at the DFT(B3LYP)/6-311+...
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