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Interactions of Copper (II) Chloride with ß-Cyclodextrin in Aqueous Solutions
Ribeiro, A. C. F.; Esteso, M. A.; Lobo, V. M. M.; Valente, A. J. M.; Simões, S. M. N.; Sobral, A. J. F. N.; Ramos, L.; Burrows, H. D.; Amado, A. M.The interaction between copper (II) chloride and the carbohydrate ß-cyclodextrin (ß-CD) has been studied in aqueous solutions (298.15 K and 310.15 K) using measurements of diffusion coefficients and electrical conductivity. Significant effects on the electrical conductivity were observed in the presence of the ß-CD, suggesting interactions between this carbohydrate and copper chloride. Support for this came fro...
Interactions of vanadates with carbohydrates in aqueous solutions
Ribeiro, Ana C. F.; Valente, Artur J. M.; Lobo, Victor M. M.; Azevedo, Eduarda F. G.; Amado, Ana M.; Costa, A. M. Amorim da; Ramos, M. LuísaThe interaction between the vanadate ion (VO3-, i.e. vanadium (V)) and the carbohydrates sucrose, glucose and fructose has been studied in aqueous solutions (pH [approximate]6, 298.15 K) using measurements of diffusion coefficients, electrical conductivity, Raman and multinuclear NMR spectroscopy. With sucrose and glucose, indications of hydrolysis of the anion in the absence of the sugars came from a decrease ...
Raman spectra of putrescine, spermidine and spermine polyamines and their N-deu...
Costa, A. M. Amorim da; Marques, M. P. M.; Carvalho, L. A. E. Batista deThe experimental and calculated Raman spectra of the N-hydrogenated and N-deuterated biogenic polyamines putrescine, spermidine and spermine and of their N-hydrogenated and N-deuterated hydrochloride salts in the 2000-3400 cm-1 spectral region (at distinct temperatures) are reported and analysed. A complete assignment of the N-H, C-H and N-D stretching modes is carried out, in the light of both steric and hydro...
The carbon---hydrogen stretching region of the Raman spectra of 1,6-hexanediami...
Costa, A. M. Amorim da; Marques, M. P. M.; Carvalho, L. A. E. Batista deThe Fermi resonance interaction between the methylene symmetric C---H stretching mode and appropriate binary combinations involving the methylene bending mode in the Raman spectra of polyamines, namely in 1,6-hexanediamine derivatives, under different conditions of deuteration and ionisation of the head amino groups and varying temperature has been analysed. The tentative assignment of the observed bands in the...
Cation hydration in hydrogelic polyacrylamide-phosphoric acid network: A study ...
Costa, A. M. Amorim da; Amado, A. M.The effects upon the structure and morphology of adding lithium, calcium and magnesium chlorides to a phosphoric acid/polyacrylamide 2:1 molar ratio proton conducting hydrogel are examined by observing the changes in the vibrational features of the polyacrylamide chain, in the phosphate group and in the interstitial water molecules as a function of the concentration and the cationic nature of the additive, at 2...
Evidence of C−H···O Hydrogen Bonds in Liquid 4-Ethoxybenzaldehyde by NMR and Vi...
Marques, M. P. M.; Costa, A. M. Amorim da; Ribeiro-Claro, Paulo J. A.Raman, FTIR, and NMR (both 13C and 17O) spectroscopies are used in a complementary way in order to study the occurrence of C−H···O intermolecular hydrogen bonds in liquid 4-ethoxybenzaldehyde (4EtOB). Additional information concerning the structure of the possible dimers is obtained through ab initio calculations, at the B3LYP/6-31G* level. The strongest evidences of the presence of C−H···O hydrogen bonds in th...
C-H...O Bonded Dimers in Liquid 4-Methoxybenzaldehyde
Karger, N.; Costa, A. M. Amorim da; Ribeiro-Claro, Paulo J. A.To further investigate the formation of C−H···O bonded dimers in liquid 4-methoxybenzaldehyde (4MeOB), previously suggested by Raman observations, 1H and 17O NMR chemical shift studies have been carried out for solutions of 4MeOB in CCl4. In addition, Raman and FTIR spectra have been obtained and a set of ab initio calculations has been performed in order to determine possible dimer structures. Considering the ...
Hydrogen-Bonded Dimers of CH3OCH2CH2OH: Ab Initio Structures and Multivariate A...
Gil, Francisco P. S. C.; Costa, A. M. Amorim da; Bruns, Roy E.; Teixeira-Dias, J. J. C.Structures and vibrational frequencies of relevant hydrogen-bonded dimers of 2-methoxyethanol are obtained at the 3-21G*//Ah41 level (the 3-21G* basis set included polarization functions deliberately added to second period atoms) and the results analyzed by standard multivariate methods. Dimers built from the same pair of isolated monomers belong to the same homologous series. The most stable dimer is obtained ...
Conformational Analysis of CmH2m+1OCH2CH2OH (m = 1-4): The Role of CH.cntdot..c...
Gil, Francisco P. S. C.; Costa, A. M. Amorim da; Teixeira-Dias, J. J. C.Structures and energies of the more stable conformations of C ~ H ~ ~ + I O C H ~ C(HCm~EOl, Hm = 1-4) have been determined by gradient geometry refinement at ab initio level. For m = 3 (C~EIa)n d m = 4 (C~EI )t,h e results show that attractive CH-O intramolecular interactions associated with the formation of five-membered rings in the alkylic fragments of these molecules lead to the stabilization of gauche arr...
Oxygen-by-Sulfur Substitution in CH3OCH2CH2OH: An Ab Initio Comparative Study o...
Gil, Francisco P. S. C.; Costa, A. M. Amorim da; Teixeira-Dias, J. J. C.Conformational energies, structural parameters and vibrational frequencies for the tgg’, ggg’, ttg, and ttt conformers of CH~XCH~CHZY(XH, Y = 0, S) have been determined by MO ab initio calculations at the MP2/6-31G* level. The results show that the relative strength of the intramolecular X. *HY interaction in tgg’ and ggg‘ conformers diminishes gradually along the series of molecules (0,O) - (0,s) - (S,O) - (S,...
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