Estudo de um conversor push-pull alimentado em corrente com grampeamento ativo /

Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico

Nicotinohydrazide

The title mol­ecule (alternative name: pyridine-3-carbohydrazide; C6H7N3O) was obtained from the reaction of ethyl nicotinate with hydrazine hydrate in methanol. In the amide group, the C—N bond is relatively short, suggesting some degree of electronic delocalization in the mol­ecule. The stabilized conformation may be compared with those of isomeric compounds picolinohydrazide (pyridine-2-carbohydrazide) and isonicotinohydrazide (pyridine-4-carbohydrazide). In the title isomer, the pyridine ring forms an angle of 33.79 (9)° with the plane of the non-H atoms of the hydrazide group. This lack of coplanarity between the hydrazide functionality and the pyridine ring is considerably greater than that observed in isonicotinohydrazide (dihedral angle = 17.14°), while picolinohydrazide is almost fully planar. The title isomer forms inter­molecular N—H⋯O and N—H⋯N hydrogen bonds, which stabilize the crystal structure

2-All­yloxy-5-nitro­benzoic acid

The mol­ecule of the title compound, C10H9NO5, is approximately planar, with the mean planes of the nitro, carboxyl and all­yloxy groups rotated by 8.1 (3), 7.9 (3) and 4.52 (18)°, respectively, from the plane of the benzene ring. Bond lengths in the aromatic ring are influenced by both electronic effects and strain induced by ortho-substitution. In the crystal structure, centrosymmetrically related mol­ecules are paired into dimers through strong O—H⋯O hydrogen bonds

Novel Supramolecular Nanoparticles Derived From Cucurbit[7]uril and Zwitterionic Surfactants

Binding constants, Log K ≈ 6.6 M-1, and NMR characterization of the complexes formed by sulfobetaines and cucurbit[7]uril (CB7) support the electrostatic interaction as major driving force. This very strong binding motif is cross-linked by additional CB7 molecules resulting in the formation of supramolecular nanoparticles (SNPs) with an average diameter of 172 nm and negative surface potential. The time course evolution of the particle size and the surface potential suggests the very fast formation of an amorphous aggregate that absorbs additional amount of sulfobetaine. These aggregates afford very stable (more than two weeks) nanoparticles in aqueous dispersion. The reversibility of the sulfobetaine/CB7 host:guest complexes allows SNPs disaggregation by adding a competitive guest as shown by treatment with tetraethylammonium chloride. The addition of this competitive cation triggers a SNPs to micelle transition. The potential application of these nanoparticles as drug delivery vehicles was investigated by using carboxyfluorescein. These experiments revealed that upon externally induced disruption of the SNPs (by tetraethylammonium chloride) the fluorescent dye was trapped into micellar aggregates that can be further disrupted by cyclodextrin additionhttp://www.usc.es/Financial support from Ministerio de Economia y Competitividad of Spain (projects CTQ2014-55208-P, CTQ2017-84354-P, CTQ2014-59646-R and MAT2015-67458-P), Xunta de Galicia (GR 2007/085; IN607C 2016/03 and Centro singular de investigación de Galicia accreditation 2016-2019, ED431G/09) and the European Union (European Regional Development Fund – ERDF), is gratefully acknowledged. J.M. received a Ramón y Cajal (RYC-2013- 13784) and a starting grant from the ERC (DYNAP677786)S

Kinetic and thermodynamic study of the interaction of vitamine B₁₂a with ligands in aqueous and micellar environments

Vita.Rate constants for the formation, k₁(superscript app) and decomposition, k₋ ₁(superscript app), of glycine, imidazole, sodium azide, cysteine, N-butanoyl-D,L-cysteine, N-octanoyl-D,L-cysteine, and N-decanoyl-D,L-cysteine adducts of vitamin B₁₂(subscript a) have been determined in water, in aqueous micellar sodium dodecyl sulfate and hexadecyltrimethylammonium bromide as well as in dodecylammonium propionate solubilized water in benzene. Effects in aqueous micellar systems are relatively small, with the exception of the N-alkanoyl-D,L-cysteine derivatives, and are explicable in terms of electrostatic and hydrophobic considerations. Using the obtained linear correlations between the glycine solubilities versus solvent polarity parameter E (subscript T)(30) , the effective environment was determined to depend on both the concentrations of water and of surfactant. Vitamin B₁₂(subscript a) effectively shielded from the apolar solvent by some 300 surfactant molecules. Values for k₁ (superscript app) and k₋₁(superscript app) for the interaction of vitamin B ₁₂(subscript a) a with ligands in the polar cavities of surfactants in benzene are significantly greater than those in bulk water and also depend on both the water and surfactant concentrations. Not unexpectedly, the largest rate enhancements were found with the smallest water pools. For the reaction of glycine with vitamin B₁₂(subscript a) at constant concentration of solubilized water for k₁ (superscript app) and k₋₁ (superscript app) increase with increasing dodecylammonium propionate concentration up to a maximum after which they decrease logarithmically. The significance of these results is discussed

Kinetic and thermodynamic study of the interaction of vitamine B₁₂a with ligands in aqueous and micellar environments

Vita.Rate constants for the formation, k₁(superscript app) and decomposition, k₋ ₁(superscript app), of glycine, imidazole, sodium azide, cysteine, N-butanoyl-D,L-cysteine, N-octanoyl-D,L-cysteine, and N-decanoyl-D,L-cysteine adducts of vitamin B₁₂(subscript a) have been determined in water, in aqueous micellar sodium dodecyl sulfate and hexadecyltrimethylammonium bromide as well as in dodecylammonium propionate solubilized water in benzene. Effects in aqueous micellar systems are relatively small, with the exception of the N-alkanoyl-D,L-cysteine derivatives, and are explicable in terms of electrostatic and hydrophobic considerations. Using the obtained linear correlations between the glycine solubilities versus solvent polarity parameter E (subscript T)(30) , the effective environment was determined to depend on both the concentrations of water and of surfactant. Vitamin B₁₂(subscript a) effectively shielded from the apolar solvent by some 300 surfactant molecules. Values for k₁ (superscript app) and k₋₁(superscript app) for the interaction of vitamin B ₁₂(subscript a) a with ligands in the polar cavities of surfactants in benzene are significantly greater than those in bulk water and also depend on both the water and surfactant concentrations. Not unexpectedly, the largest rate enhancements were found with the smallest water pools. For the reaction of glycine with vitamin B₁₂(subscript a) at constant concentration of solubilized water for k₁ (superscript app) and k₋₁ (superscript app) increase with increasing dodecylammonium propionate concentration up to a maximum after which they decrease logarithmically. The significance of these results is discussed