Jucleiton José R. de Freitas

SYNTHESIS OF AMIDOXIMES USING AN EFFICIENT AND RAPID ULTRASOUND METHOD

This is a report on an efficient and rapid synthesis of amidoximes using ultrasound irradiation with appropriate nitrile and hydroxylamine hydrochloride in water/ethanol. This new synthetic methodology is compared with previously known methods. The main advantages of the process reported are shorter reaction times, easier work-up, and good yield.

A CONVENIENT SYNTHESIS AND CYTOTOXIC ACTIVITY OF 3-ARYL-5-PENTYL-1,2,4-OXADIAZOLES FROM CARBOXYLIC ACID ESTERS AND ARYLAMIDOXIMES UNDER SOLVENT-FREE CONDITIONS

The synthesis of 3-aryl-5-pentyl-1,2,4-oxadiazoles from carboxylic acid esters and arylamidoximes in the presence of potassium carbonate is described. The reaction was carried out in a microwave oven without any solvent in much shorter time and in good yields. The structures of the synthesized compounds were elucidated using IR, 1H and 13C NMR spectroscopy and elemental analysis and their antiproliferative activities was evaluated against three different human cell lines.

PREPARAÇÃO DE 1,2,4-OXADIAZOL: SEQUÊNCIA DIDÁTICA APLICADA EM DISCIPLINA DE SÍNTESE ORGÂNICA NA GRADUAÇÃO

1,2,4-oxadiazoles are used in a wide range of applications, including medicinal chemistry and chemistry of materials. However, this kind of oxadiazoles is not usually prepared in an undergraduate organic teaching laboratory. This work describes a didactic sequence for the preparation of 1,2,4-oxadiazols, mediated by microwave irradiation, employing home-use microwave oven. For the development of this practice, one lecture and one laboratory session were used. At the end of this session, a questionnaire was applied to evaluate the didactic sequence. The conclusion was that this approach can be used for the preparation of 1,2,4-oxadiazoles as a pedagogical practice to make the process of teaching easier and enjoyable.

Extração e separação cromatográfica de pigmentos de pimentão vermelho: utilização de materiais alternativos

Normal 0 21 false false false A separacao cromatografica utilizando pigmentos extraidos de produtos naturais proporciona uma abordagem didatica e interessante para o estudante do ensino medio, e permite o acompanhamento de uma separacao pela simples observacao das cores dos pigmentos possibilitando uma correlacao entre a Quimica e o cotidiano. Este artigo descreve um experimento de extracao e separacao cromatografica de pigmento de pimentao utilizando materiais alternativos. No experimento usou-se a farinha de trigo como fase estacionaria, e o removedor de gordura e de esmaltes como solventes. O experimento permitiu ilustrar conceitos de misturas, substâncias, solubilidade, polaridade e de funcoes orgânicas. Vale salientar que metodologia alem de ilustrativa e de utilizar materiais alternativos, mostrou-se bastante eficiente na separacao dos principais componentes do pimentao vermelho.

Investigando cinza da casca do arroz como fase estacionária em cromatografia: uma proposta de aula experimental nos cursos de graduação

This article describes an experiment that involves the extraction and separation of the pigments of spinach extract by column chromatography using the silica obtained from rice husk ash as a stationary phase. The experimental procedure is very simple to apply in the chemistry laboratory, and allowed to illustrate some concepts of organic chemistry: structure of organic molecules, solubility, polarity, extraction, partition coefficient, adsorption and retention factor (Rf), as well as objectives and fundamentals of chromatographic methods. The experiment can be carried out in a 4 h period.

Synthesis of aryl-1H-1,2,3-triazoles via 1,3-dipolar cycloaddition

A series of Aryl-1H-1,2,3-triazoles were prepared from the reaction between aril-azide (1) with 1.5 equiv. of terminal alkynes (2a-o). The reactions carried out at room temperature and in the presence of CuI (10 mol%) in acetonitrile. The compounds (3a-o) were obtained in moderate-to-good yields (50-94%). In general, not was observed significant inductive effect on the reactivity of the alkynes (2a-f). The alcohol alkynes (2i-k) showed moderate yields 50-72%. On the other hand, the reaction with alkyl alkynes (2m,n) furnished the compounds (3m) and (3n) in excellent yields of 89% and 90%, respectively.

Separação de Mistura Sólido–Sólido : Novo Enfoque Experimental

Neste artigo, um novo metodo experimental e apresentado na separacao de mistura solido-solido, usando materiais baratos e simples. As atividades propostas foram divididas em dois momentos distintos: a) construcao de equipamentos; b) realizacao de experimentos para gerar resultados a serem interpretados. Estas atividades possibilitam a construcao de conceitos, por exemplos, solubilidade, substâncias, misturas, dissolucao, combustao e inflamavel.

Modelos Mentais dos Estudantes do Ensino Médio e a Química dos alimentos

Modelo Mental e definido como representacao de uma ideia, objeto, evento, processo ou sistema. O conceito de modelo mental vem sendo usado em varias areas do conhecimento. Baseado na Teoria dos Modelos Mentais de Johnson-Laird, estudantes de Ensino Medio foram observados durante dois semestres letivos com a finalidade de determinar o tipo de modelo mental que eles teriam utilizados durante a abordagem da tematica quimica dos alimentos.