Encontrados 13 documentos, a visualizar página 1 de 2
Study of Nα-benzoyl-L-argininate ethyl ester chloride, a model compound for pol...
Fonseca, A. C.; Jarmelo, S.; Silva, M. Ramos; Beja, A. M. Matos; Fausto, R.; Gil, M. H.; Simões, P. N.Poly(ester amide)s (PEAs) are lacking in structural and spectroscopic information. This paper reports a structural and spectroscopic characterization of Nα-benzoyl-L-argininate ethyl ester chloride (BAEEH+·Cl−), an important amino acid derivative and an adequate PEAs’ model compound. Crystals of BAEEH+·Cl− obtained by slow evaporation in an ethanol/water mixture were studied by different complementary technique...
Épocas de floração de cultivares de oliveira em Castelo Branco, Elvas e Santarém
Cordeiro, A.M.; Martins, P.C.S.; Matias, H.; Rogado, B.; Silva, M.; Ramos, A.S.Comunicação apresentada no III Simpósio Nacional de Olivicultura que decorreu em Castelo Branco, de 29 a 31 de Outubro, na Escola Superior Agrária do Instituto Politécnico de Castelo Branco. ; A época de floração da oliveira está determinada pelas características genéticas inerentes a cada cultivar e é influenciada por factores climatéricos, variáveis de ano para ano. Esta influência do clima pode provocar imp...
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...
The structure of betaxolol from single crystal X-ray diffraction and natural bo...
Canotilho, João; Castro, Ricardo A. E.; Rosado, Mário T. S.; Silva, M. Ramos; Beja, A. Matos; Paixão, J. A.; Redinha, J. SimõesThe structure of betaxolol obtained from ethanol:water solution was studied by X-ray diffraction. The geometrical parameters needed to define the structure are tabulated. The X-ray data show the existence of two conformers in the unit cell differing only in the conformation of the cyclopropylmethoxy fragment. Differences in the bond lengths angles and dihedral between both conformations are observed. The cyclop...
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...
X-ray diffraction and Mössbauer spectrometry studies of molecular iron compounds
Costa, B. F. O.; Greneche, J. M.; Silva, M. Ramos; Pereira, L. C. J.We have synthesized two new iron complexes that have been structural and magnetically characterized: diphenylguanidinium hexafluoroferrate and hexakisvaline-oxo-triiron(III) chloride. The former crystallizes as monomers with the fluoride ions six-coordinating the Fe(II) ion. Valine iron chloride is comprised of trinuclear complexes, with a well ordered oxo-centered carboxylate core and some disordered organic l...
Crystal and Molecular Structure of 4,6-Bis(nitroimino)-1,3,5-triazinan-2-one: ...
Simões, P. N.; Pedroso, L. M.; Beja, A. M. Matos; Silva, M. Ramos; MacLean, Elizabeth; Portugal, A. A.This paper provides an overview of recent progress on structural data on the title compound. Theoretical work based on quantum mechanical calculations was performed to gain some understanding on the heterocyclic tautomerism potentially exhibited by the compound. The computational studies encompassed a wide range of tautomers/conformers, allowing the determination of the most probable molecular structure. In the...
Conformational Isomorphism of Organic Crystals: Racemic and Homochiral Atenolol
Castro, R. A. Esteves de; Canotilho, João; Barbosa, Rui M.; Silva, M. Ramos; Beja, A. Matos; Paixão, J. A.; Redinha, J. SimõesX-ray diffraction analysis of (R,S)- and S-atenolol crystalline forms was performed. The crystals studied were grown from evaporation of an ethanol/water solution. (R,S)-Atenolol crystallizes in the centrosymmetric space group C2/c, and S-atenolol crystallizes in a noncentrosymmetric space group C2. There is one symmetry independent molecule in (R,S)-atenolol crystals and two symmetry independent molecules in S...
One-step synthesis of dipyrromethanes in water
Sobral, Abílio J. F. N.; Rebanda, Nuno G. C. L; Silva, Melo da; Lampreia, Sandra H.; Silva, M. Ramos; Beja, A. Matos; Paixão, J. A.In this communication we describe the first results of an efficient synthesis of [beta]-free-dipyrromethanes in water. This new method affords very pure products in moderate to high yields, using a cheap, non-toxic, environment friendly solvent, in a one-step procedure from pyrrole and carbonyl compounds, needing little or no work up procedures. ; http://www.sciencedirect.com/science/article/B6THS-48FBYP9-W/...
Low temperature polymorphism in 3-amino-1-propanol
Cacela, C.; Baudot, A.; Duarte, M. L.; Matos-Beja, A. M.; Silva, M. Ramos; Paixão, J. A.; Fausto, R.3-Amino-1-propanol (3AP) was investigated by differential scanning calorimetry, and low temperature powder X-ray diffraction and Raman spectroscopy. Within the range of temperatures studied (-150-25 °C), 3AP was found to be able to crystallize in two monotropic polymorphs. Fast cooling rates produce an amorphous state that, on heating, crystallizes into the metastable polymorph. At higher temperatures, this met...
| Financiadores do RCAAP | |||||||
|
|
|
|
|
|
||