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Molecular simulation has become an integral and invaluable part of Chemical Product Engineering, as it provides fundamental and indispensable insights for a rational product design. Silica aerogels...

We report an alternative method for the synthesis of 2-(1,3-dithian-2-ylidene)-acetonitrile using 3-(4-chlorophenyl)-3-oxopropanenitrile and carbon disulfide as starting materials. The methanolysis of the intermediate 3-(4-chlorophenyl)-2-(1,3-dithian-2-ylidene)-3-oxopropanenitrile occurs via three possible intermediates, leading to the formation of the product at a 75% overall yield. Molecular modeling simulation of the reaction pathway using B3LYP 6-311G++(2df,2p) justified the proposed reaction mechanism.

In the present paper, we propose the construction of a physical molecular model through the reuse of recyclable polymeric material, selected in units of selective garbage collect and in the school environment itself. This didactic intervention, especially in the Organic Chemistry classes, greatly helps the students have a threedimensional visualization of the molecules, averting itself, thus, the two-dimensional classicism of the whiteboard and the book. The construction of this handmade learning object has some extremely important characteristics both from an operational point of view of its elaboration as to the didactic point of view. Among them, we can quote: a very low cost; simplicity in the making and enforcement; a good approximation in the representation of the geometries of the molecules and the bond angles to the experimental values. The proposed model could substitute the ones sold on the market without any loss of information, moreover it adds some information that only this model is able to highlight, like the different size of the atoms. None of the representational physical models (either a model sold on the market or a handmade one) provides the discussion about the strength of the link. The model proposed here, however, has sticks with different length purposely, inducing the student to think about and verify the reason of this differentiation. Still regarding the process of learning, we can observe, in an workshop, that the involvement of the students in the making of the molecular kit favors their effective participation as an strategy and a way of a meaningful learning, functioning as a very efficient subsumptive. We still evidence the potential of this project in make the students sensible to the environmental consciousness, in view of the characteristics of the utilized material, indiscriminately discarded in the trash. Furthermore, some workshops were developed with teachers and students of the Public Educational System in the town of Arapiraca-AL. In the occasion, some quizzes were applied about the perception of the students and we observed, in most answers, that the use of the recycled material led to some discussions about what really trash is, this way what we’re going to do to minimize the problems caused by its consume and posterior discard and how to be rightly reused. No presente trabalho, propomos a construção de um modelo molecular físico por meio do reuso de material polimérico reciclável, selecionados em unidades de coleta seletiva de lixo e no próprio ambiente escolar. Essa intervenção didática, especialmente nas aulas de Química Orgânica, vem auxiliar sobremaneira o aluno a ter uma visualização tridimensional das moléculas, distanciando-se, assim, do classicismo bidimensional da lousa e do livro. A construção desse objeto de aprendizagem possui algumas características extremamente importantes tanto do ponto de vista operacional de sua elaboração, quanto do ponto de vista didático. Dentre elas, podemos citar: o baixíssimo custo; simplicidade de confecção e aplicação; uma boa aproximação na representação das geometrias das moléculas e dos ângulos de ligações aos valores experimentais. O modelo proposto pôde substituir os modelos comerciais sem qualquer perda de informação, inclusive acrescenta informações que somente esse modelo consegue dar destaque, como o tamanho diferenciado dos átomos. Nenhum dos modelos representacionais físicos, seja comercial ou artesanal, traz a discussão sobre a força de ligação. Entretanto, o modelo aqui proposto possui, propositalmente, varetas de diferentes comprimentos, induzindo o aluno a refletir e verificar o porquê dessa diferenciação. Ainda no que diz respeito ao processo de aprendizagem, pudemos observar que o envolvimento dos alunos e do professor na confecção do kit molecular propiciou a participação efetiva dos mesmos como estratégia e forma de aprendizagem significativa, funcionando como um subsunsor bastante eficaz. Ressaltamos ainda, o potencial desse projeto em sensibilizar uma conscientização ambiental, dado às características dos materiais utilizados, descartados no lixo indiscriminadamente. Além disso, foram desenvolvidas oficinas com professores e alunos da rede pública de ensino no município de Arapiraca-AL. Na ocasião, foram aplicados questionários sobre a percepção dos alunos e se observou, na grande maioria das respostas, que o uso de material reciclado levou a discussões sobre o que realmente é lixo, por conseguinte o que faremos para minimizar os problemas causados por seu consumo, posterior descarte e como ser adequadamente reaproveitados.

Molecular modeling enables the students to visualize the abstract relationships underlying theoretical concepts that explain experimental data on the molecular and atomic levels. With this aim we used the free software "Arguslab 4.0.1" (semi-empirical method) to study the reaction of 1-chloropropane with ethoxide in solution, known to lead to methyl propyl ether, through the S N2 mechanism, and propene, through the E2 mechanism. This tool allows users to calculate some properties (i. e. heat formation or electric charges) and to produce 3D images (molecular geometry, electrostatic potential surface, etc.) that render the comprehension of the factors underlying the reaction's progress, which are related to the structure of the reagents, and the process kinetic clearer and easier to understand by the students

In general, molecular modeling techniques applied in medicinal chemistry have been static and drug based. However the active site geometry and the intrinsic flexibility of both receptor and ligand are fundamental properties for molecular recognition and drug action. As a consequence, the use of dynamic models to describe the ligand-receptor complex is becoming a more common procedure. In this work we discuss the relevance of considering the receptor structure in medicinal chemistry studies as well as the flexibility of the ligand-receptor complex.

A series of seven Schiff bases have been synthesized from 3,3-diphenylpropilamine and substituted benzaldehydes. These imines were treated with NaBH4 in ethanol affording the corresponding amines in 98-55% yields. A molecular modeling study was performed with the Schiff bases in order to compare the theoretical parameters with the experimental results. The theoretical parameters were obtained by AM1 and PM3 semi-empirical methods. The analysis of charge, electron densities and LUMO coefficients suggested that the most favorable interactions should occur with Schiff bases containing electron-donating groups, in accordance with experimental yields, showing that the higher reactivity is due to higher electrophilic character of imine carbons.

The results of semiempirical molecular orbital calculations performed on aziridinone and diaziridinone employing the MNDO, AM1, and PM3 molecular models are presented. The AM1 method, which best reproduces ground-state molecular properties, is used to calculate electronic parameters and the use of these parameters for the evaluation of reactivity is discussed.