Educação Química no Projeto Escolar “Quixaba”: Alfabetização Científica com Enfoque CTSA no Ensino Fundamental a Partir de Temas Sociocientíficos

The objective of this study was to analyze the pedagogical aspects of teaching chemistry in a “Quixaba” school project developed with students of Science of last year of basic school (corresponding to the third cycle), focusing CTSA. The project dealt with the articulation of socio-scientific issues with content of Chemistry, focusing on some industry sectors of Espírito Santo State, such as food, construction and steel. This is a case study, qualitative, based on direct observations, technical visits and focus group interviews. The results led us to conclude that the teaching practices carried out during the “Quixaba” project provided scientific literacy focusing CTSA. DOI: http://dx.doi.org/10.17807/orbital.v7i1.68

Fast and efficient synthesis of pyrano[3,2-c]quinolines catalyzed by niobium(V) chloride

A highly efficient two-step method for the synthesis of pyranoquinoline derivatives from imino-Diels-Alder reactions between aldimines and 3,4-dihydro-2H-pyran using niobium(V) chloride as catalyst under mild conditions is described.Fundacao de Amparo Pesquisa do Estado de Sao Paulo (FAPESP)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Coordenadoria de Aperfeicoamento de Pessoal do Nivel Superior (CAPES)Financiadora de Estudos e Projetos (FINEP

Niobium to alcohol mol ratio control of the concurring esterification and etherification reactions promoted by NbCl5 and Al2O3 catalysts under microwave irradiation

Alcohols and acids can be switched to produce ethers or esters by varying the alcohol to catalyst mol ratio, in a new etherification and esterification method using NbCl5/Al2O3 catalyst under ""solvent free"" conditions and promoted by MW (microwave) irradiation. A ""two sites"" mechanism for the reaction is proposed, in an attempt to clarify the tendency of the catalyst to be dependent on the alcohol alone during the esterification process. (c) 2008 Elsevier B.V. All rights reserved

Using NMR to Study the Process of Rigid Polyurethane Depolymerization

Polyurethanes (PUs) have been widely used in several trade sections. Thereby, large amounts of waste are produced and need to be correctly disposed of. Research on this theme has been helping industries to apply recycling processes that are cheap and efficient. In this work, the glycolysis of a rigid PU was performed using different catalysts. 1H NMR analysis was used to obtain the rate of PU depolymerization. Glycerol (GCL) and diethylene glycol (DEG) were tested as glycolysis agents. The PU was synthesized to be free of additives in the depolymerization process, and its characterization was performed using FTIR and 1H NMR analyses. The use of NaOH as a catalyst showed a better conversion rate, as is already known in the literature. Ionic liquids (LIs) also presented good results, which can be improved by modifying the reaction conditions. To determine the composition of the mixture of products in the depolymerization reaction, diffusion ordered spectroscopy 1H NMR (DOSY-NMR) was used. DOSY-NMR indicated a complex mixture of reaction by-products, differently from the 1H NMR data, which indicated the formation of a simple diamine-terminated by-product. DOI: http://dx.doi.org/10.17807/orbital.v11i1.1385<br /

Niobium(V) Chloride as Catalyst in Diels-Alder Reaction of Furan Ring

According to the relevant literature, the Diels-Alder reaction of furan without a catalyst can last several weeks and shows a low yield due to the diene's low reactivity. The use of Lewis acid catalysts or high pressures is described as an effective method for improving the reaction yields. This paper describes our recent study on the use of niobium pentachloride as the catalyst in Diels-Alder reactions between furan and several reactive dienophiles, among which methyl acrylate showed good yields, especially at lower temperatures. Other dienophiles have shown lower yields because of problems such as byproduct formation and the high reversibility of the reaction

SÍNTESE E DETERMINAÇÃO DA ESTEREOQUÍMICA RELATIVA DE UM NOVO EPÓXIDO ALDEÍDO CICLOPENTANO MONOTERPENÓIDE

In this study, we report the preparation of a new tetra-substituted epoxide aldehyde cyclopentane, which acts as a starting material for the synthesis of plinol, from (R)-(+)-epoxy-limonene. The synthesis was performed in three steps and resulted in a good yield. The structural determination was performed by 1H and 13C NMR, and the relative stereochemistry was defined by nuclear Overhauser effect (NOE) experiments with computer calculations of molecular modeling, particularly with respect to indirect coupling constant calculations