Solvolysis
Mostrando 1-12 de 17 artigos, teses e dissertações.
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1. Topological study of the first step of nucleophilically unassisted solvolysis of protonated 2-endo/exo-norbornanol and protonated 2-endo/exo-oxabicycloheptanol
A assistência da deslocalização de elétrons sigma ou assistência anquimérica dos elétrons sigma explica grandes diferenças de velocidade na solvólise de 2-exo- e 2-endo-norbornil-p-bromobenzenosulfonatos. Este estudo foi anteriormente analisado pela teoria dos orbitais moleculares em fase gás. Ao revisitar este antigo problema a partir da teoria qu
Journal of the Brazilian Chemical Society. Publicado em: 2012-03
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2. Gas-phase solvolysis type reactions of SiCl3+ cations
Gas-phase SiCl3+ ions undergo sequential solvolysis type reactions with water, methanol, ammonia, methylamine and propylene. Studies carried out in a Fourier Transform mass spectrometer reveal that these reactions are facile at 10-8 Torr and give rise to substituted chlorosilyl cations. Ab initio and DFT calculations reveal that these reactions proceed by ad
Química Nova. Publicado em: 2010
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3. Solvolysis reactions of cation +SiCl3: Experiment and Theory / Reações de solvólise em fase gasosa do cátion +SiCl3: experimento e teoria
Polyhalogenated silicenium ions, X3Si+ (X = F, Cl), are common fragment ions in the mass spectra of polyhalogenated silanes obtained by electron ionization. These ions are powerful electrophiles and are believed to play a role in plasma enhanced corrosion processes and plasma enhanced chemical vapour deposition processes. In this dissertation, we present som
Publicado em: 2010
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4. SÃntese e estudo espectroscÃpico de complexos de Ãons lantanÃdeos incorporados em materiais hÃbridos orgÃnicos-inorgÃnicos
In this work two new europium and gadolinium b-diketonate complexes, [Ln(btfa)3(4,4 -bpy)(EtOH)] (Ln = Eu, Gd; 4,4 -bpy = 4,4 -bipyridine; btfa = 4,4,4- trifluoro-l-phenyl- 1,3-butanedione), were prepared and incorporated into a organicinorganic hybrid material. The general formulae of these complexes were confirmed by X-rays single crystal data and elementa
Publicado em: 2007
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5. Partial characterization and anticoagulant activity of a heterofucan from the brown seaweed Padina gymnospora
The brown algae Padina gymnospora contain different fucans. Powdered algae were submitted to proteolysis with the proteolytic enzyme maxataze. The first extract of the algae was constituted of polysaccharides contaminated with lipids, phenols, etc. Fractionation of the fucans with increasing concentrations of acetone produced fractions with different proport
Brazilian Journal of Medical and Biological Research. Publicado em: 2005-04
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6. THE SLOW RATES OF SOLVOLYSIS OF ENDO-5,6-TRIMETHYLENE-ENDO-(2 AND 8)-NORBORNYL TOSYLATES: STERIC HINDRANCE TO IONIZATION AND THE FOOTE-SCHLEYER CORRELATION*
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7. Reexamination of the presence and linkage of 3-hydroxybutyryl substituents in the acidic capsular polysaccharide of Rhizobium trifolii 0403.
We resolved previous conflicting results concerning the presence of 3-hydroxybutyryl substituents on the extracellular acidic polysaccharide from Rhizobium trifolii 0403. These substituents were indeed present in the polysaccharide and in the oligosaccharide fragments obtained by hydrogen fluoride solvolysis of the extracellular and capsular polysaccharides
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8. Direct C-1 hydroxylation of vitamin D compounds: convenient preparation of 1alpha-hydroxyvitamin D3, 1alpha, 25-dihydroxyvitamin D3, and 1alpha-hydroxyvitamin D2.
An efficient procedure for the direct C-1 hydroxylation of vitamin D compounds has been developed. The method involves conversion of vitamin D3 tosylates to 3,5-cyclovitamin D derivatives, allylic oxidation with selenium dioxide, and acid-catalyzed solvolysis to the 1 alpha-hydroxyvitamin D analogs. When applied to vitamin D3,25-hydroxyvitamin D3, and vitami
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9. A mechanism for posttranslational modifications of proteins by yeast protein farnesyltransferase.
Protein farnesyltransferase catalyzes the alkylation of cysteine in C-terminal CaaX sequences of a variety of proteins, including Ras, nuclear lamins, large G proteins, and phosphodiesterases, by farnesyl diphosphate (FPP). These modifications enhance the ability of the proteins to associate with membranes and are essential for their respective functions. Th
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10. The Acid-Base Properties, Hydrolytic Mechanism, and Susceptibility to O2 Oxidation of Fe4S4(SR)4-2 Clusters
The iron-sulfur cluster compounds Fe4S4(SR)4-2 [where —SR = —SCH3, —S—C(CH3)3, and —S— CH2—CH(CH3)2] have been found to represent the base species of weak acids of pKa comparable to that of carboxylic acids. The acid species Fe4S4(SR)4H- is most subject to reaction with O2 and to acid-catalyzed solvolysis, while the base species Fe4S4(SR)4-2 mo
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11. The Selectivity Principle and the Question of the Bridged Structure of the 2-Norborynyl Cation
Low exo/endo rate ratios in the solvolysis of certain norbornyl derivatives have been attributed to the involvement of classical (unbridged) 2-norbornyl cations. Consequently, the high exo/endo rate ratio in the parent system, 2-norbornyl arenesulfonates, has been interpreted as involving rate enhancement in the exo isomer arising from σ-participation. It i
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12. Familial giant cell hepatitis associated with synthesis of 3 beta, 7 alpha-dihydroxy-and 3 beta,7 alpha, 12 alpha-trihydroxy-5-cholenoic acids.
Urinary bile acids from a 3-mo-old boy with cholestatic jaundice were analyzed by ion exchange chromatography and gas chromatography-mass spectrometry (GC-MS). This suggested the presence of labile sulfated cholenoic acids with an allylic hydroxyl group, a conclusion supported by analysis using fast atom bombardment mass spectrometry (FAB-MS). The compounds