Síntese, caracterização e estudo das propriedades catalíticas e magnéticas de nanopartículas de Ni dispersas em matriz mesoporosa de SiO2

Nickel nanoparticles supported on amorphous silica ceramic matrix were synthesized by the polymeric precursor method. The nanostructure was characterized by NMR, BET, XRD, SEM, TEM, and flame atomic absorption spectrometry techniques. It was observed a dependence of the crystallite size on the thermal annealing, under a N2 atmosphere. The materials presented a high catalytic activity and selectivity upon the beta-pinene hydrogenation reaction. The magnetic hystereses were also correlated with the morphology of the processed material.

Síntese e reatividade de azaindóis: aplicações na preparação de moléculas de interesse biológico

Synthetic methods used for the preparation of azaindoles are described in this article. Applications in the preparation of bioactive molecules are given: synthesis of substituted 6-azaindoles as benzodiazepines receptor ligands, substituted 7-azaindoles as dopamine D4 ligands and preparation of an olivacine analogue.

Uma proposta de síntese para o ensino integrado das disciplinas experimentais de química orgânica e inorgânica nos cursos de graduação

The synthesis of the layered compound VO(PO4)(H2O)2 and its use to oxidize 2-butanol to the ketone 2-butanone, is proposed as an experiment to integrate the organic and inorganic experimental undergraduate chemistry courses, in an atempt to overcome the observed disrupture between organic and inorganic chemistry.

Metodologias de síntese de 2-arilcicloexanonas

Several methodologies concerning the preparation of 2-aryl and 2-heteroarylcyclohexanones are presented. The use of these intermediates in the synthesis of chemically and biologically interesting organic compounds is also discussed.

Aspectos químicos e potencial terapêutico de imidas cíclicas: uma revisão da literatura

Cyclic imides consists of an important family of organic compounds with therapeutic potential. In this review, emphasis will be given to the chemical and biological aspects of several sub-classes of this family, incluing maleimides, succinimides, glutarimides, naphtalimides, etc. Additionally, will be focused the contribution of our research group in this field.

Síntese dos analgésicos paracetamol e fenacetina e do adoçante dulcina: um projeto para química orgânica experimental

A synthesis of artificial sweetener dulcin starting from nitrobenzene was elaborated for undergraduate organic laboratory course. Paracetamol and phenacetin, both physiologically active analgesic compounds, were also prepared as intermediates. Besides a large scope of discussion subjects related with organic synthesis, interesting lectures about analgesics and sweeteners may also be performed in this project. The advantage of this project is the adaptability according to the conditions offered by the course, i.e., convenience and/or availability of time and reagents.

Síntese eletroquímica do ion ferrato(VI)

The optimization of ferrate(VI) ion generation has been studied due to its favorable characteristics for application in several fields, including environmental quality control. The paper presents the best conditions for electrolytic generation of ferrate(VI) in alkaline media. An appropriate electrolyte was NaOH, 10 mol/L. Circulation of the electrolyte solution was important to avoid acidification close to the anode surface. An anode pre-cleaning with 10% HCl was more efficient than a cathodic pre-polarization. Among the distinct anode materials tested, pig iron showed the best performance, allowing up to 20 g/L of Na2FeO4, in 10 mol/L NaOH solution to be obtained, after 7 h of reactor operation, which is a concentration higher than those found in literature for alternative processes.

Síntese do isobutileno e seu emprego em reações de esterificação: propostas de aulas práticas de química orgânica para a graduação

An experiment for the synthesis of isobutylene from tert-butanol dehydratation using oxalic acid as catalyst, followed by preparations of tert-butyl benzoate and tert-butyl cinnamate is described. The synthesis are simple, requiring two periods of 4 hours and are suitable for undergraduate organic chemistry experimental courses.

Síntese e caracterização de um composto VOPO4-DMA

A layered matrix, alpha-VOPO4.2H2O was used as host species to produce a VOPO4.dimethylacetamide intercalation compound. The oxovanadium matrix and the synthesized hybrid were characterized by elemental analysis, infrared spectroscopy, thermogravimetry, X-ray diffractometry and SEM microscopy. The X-ray diffraction patterns show that the VOPO4.dimethylacetamide compound is amorphous, but can be turned lamellar after a solubilization-crystallization process. The SEM micrographs obtained for the VOPO4-dimethylacetamide hybrid matrix show that the microstructure of VOPO4.2H2O is changed after reaction, with a delamination of the oxovanadium matrix.

Síntese e avaliação da atividade fitotóxica de novos análogos oxigenados do ácido helmintospórico

Several compounds related to helminthosporic acid (3) were synthesized via the [3+4] cycloaddition. The reaction of 3-hydroxymethyl-2-methylfuran (12) with 1,1,3,3-tetrabromo-4-methylpentan-2-one (13) resulted in 7-hydroxymethyl-4alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (8) (37%) and 7-hydroxymethyl-2alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (14) (12%), which were converted into 7-formyl-4alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (16) (32% from 8) and 7-formyl-2alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (18) (40% from 14), respectively. Reduction of (8) resulted in 7-hydroxymethyl-4alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6 -en-3alpha-ol (11) (63% from 8) and 7-hydroxymethyl-4alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6-en-3 beta-ol (15) (30% from 8). The 4alpha-isopropyl-1alpha-methyl-3-oxo-8-oxabicyclo[3.2.1]oct-6-en-7-oic acid (19) was obtained by oxidation of (16) (78%). The results of biological tests are described in details. The best result was observed for compound (15) that caused 76% inhibition on the root growth of D. tortuosum.

Efeito do polietilenoglicol e da albumina na imobilização de lipase microbiana e na catálise em meio orgânico

Poly (ethylene) glycol (PEG) and bovine serum albumin (BSA), as additive agents, were used to enhance the activity of immobilized microbial lipase in organic solvent. Controlled pore silica (CPS) was selected as matrix and different immobilization procedures were evaluated: directly lipase binding on CPS and simultaneous addition of lipase and additive agent on the same support. The highest coupling yield (59.6%) was attained when the immobilization procedure was performed at lipase loading of 150 U/g support in the presence of PEG-1.500. This immobilized system was used in esterification reactions under repeated batch cycles and the biocatalyst half-life was found to increase 2.7 times when compared with the control.

Dióxido de estanho nanoestruturado: síntese e crescimento de nanocristais e nanofitas

The objectives of this work are to supply a basic background on nanostructured materials and also to report about the obtaining of nanoparticles, mainly, tin dioxide nanocrystalline particles (obtained by using the polymeric precursor method) presenting a high stability against particle growth due to the usage of a metastable solid solution. The synthesis and growth of SnO2 nanoribbons by a carbothermal reduction process are also discussed.

Sucroquímica: síntese e potencialidades de aplicações de alguns derivados químicos de sacarose

The interest on the use of sucrose as raw material increased in the last years. In this work, the synthesis and applications of sucrose derivatives as esters, ethers, and other products are discussed in a concise manner aiming to presenting the sucrochemistry as a promising field in organic chemistry from a rather accessible, low-priced, ecological, and renewable source.

Tratamento dos resíduos gerados na síntese de polianilina em escala pré-piloto

Polyaniline (PAni) is one of the most studied conducting polymer. It can be synthesized by two methods: electrochemical or chemical oxidation. The chemical oxidation is more adequate to produce large quantities of polymer. Regardless of the synthesis scale, the treatment of the residues before its final destination is very important and necessary because it contains toxic aniline derivatives (carcinogens in some cases), acids and inorganic salts, both with low toxicity. In this work we discuss the methods used to treat these residues and to eliminate and discard the toxic substances. These were extracted from the reaction residues by using activated coal and the pH of the residue was neutralized.

Alcóxidos como precursores na síntese de novos materiais através do processo sol-gel

An overview about the role of alkoxides in the most recent uses of the sol-gel process in the synthesis of new materials is presented. Special attention is focused on the uses of silicon, aluminum, zirconium and titanium alkoxides. This review shows that the alkoxides enable the synthesis of new matrices with controlled surface area, acidity and porosity, as well as some unusual properties. The property associated with the solubility of metal alkoxides opens enormous possibilities of combining them for the synthesis films of powders with a very large range of metal compositions.