Now showing items 11-20 of 1859
In situ quantification of the active acid sites of H6P2W18O62·nH 2O heteropoly-acid through chemisorption and temperature programmed surface reaction of isopropanol
(Elsevier Science, 2004-06)
Isopropanol chemisorption and temperature programmed surface reaction analyses were used to determine the nature, amount and acid strength of the active sites of bulk WO3, monolayer supported tungsten oxide over titania ...
Sobre a força de ácidos e bases: algumas consideraçõesOn the strength of acids and bases: some considerations
(Sociedade Brasileira de Química, 2008)
Understanding the influence of Lewis acids in the regioselectivity of the Diels-Alder reactions of 2-methoxy-5-methyl-1,4-benzoquinone: A DFT study
The mechanisms of the Diels-Alder (DA) reactions of 2-methoxy-5-methyl-1,4-benzoquinone 1 with 2-methyl-1,3-butadiene 2, in the absence and in the presence of LA catalysts, have been studied using the DFT method at the ...
Bronsted Acid Catalyzed Morita-Baylis-Hillman Reaction: A New Mechanistic View for Thioureas Revealed by ESI-MS(/MS) Monitoring and DFT Calculations
(Wiley-v C H Verlag Gmbh, 2009-01-01)
A Morita-Baylis-Hillman (MBH) reaction catalyzed by thiourea was monitored by ESI-MS(/MS) and key intermediates were intercepted and characterized. These intermediates Suggest that thiourea acts as an organocatalyst in all ...
Structural requirements and reaction pathways in condensation reactions of alcohols on MgyAlOx catalysts
The effect of composition and of surface properties on alcohol-coupling reactions was studied on MgyAlOx catalysts using C2H5OH or 13CH3OH/1–12C3H7OH mixtures as reactants. Samples with Mg/Al ratios of 0.5–9.0 were obtained ...
Reações ácido-base: conceito, representação e generalização a partir das energias envolvidas nas transformações
(Sociedade Brasileira de Química, 2014)
Kinetic of liquid-phase reactions catalyzed by acidic resins: The formation of peracetic acid for vegetable oil epoxidation
(Elsevier Science, 2000-05)
A heterogeneous kinetic model which takes into account the complete physicochemical interaction of reactive species in a polar liquid phase with an ion-exchange resin acting both as selective sorbent and heterogeneous ...
One-Step Synthesis of Methoxylated Phloroglucinol Derivatives Promoted by Niobium Pentachloride: An Experimental and Theoretical Approach
Phloroglucinol derivatives are an important class of natural compounds featuring the rhodomyrtone derivatives. In this work, the synthesis of compounds with a structure core of rhodomyrtosone I is described using a ...
Solid-phase Petasis multicomponent reaction for the generation of beta-lactams 3-substituted with non-proteinogenic alfa-amino acids
An efficient protocol for the rapid generation of libraries of biologically promising b-lactams is described. Key step is a solid-phase based multicomponent Petasis reaction