The contributions of Henri Victor Regnault in the context of organic chemistry of the first half of the nineteenth century

A very little known aspect of the scientific career of Regnault is his contribution to the emerging organic chemistry in the first half of the nineteenth century. The purpose of this article is not only to describe two of his most important researches in this field, as were the discovery of two series of halogenated derivates of certain organic compounds and the precise identification of some of the then recently discovered alkaloids, but also the main features that identified his research method. With the involvement in these subjects, Regnault unintentionally positioned himself in the midst of some of the polemics about the classification of organic compounds that characterized this age of science.

Uma experiência didática de corrosão usando colorimetria visual

In this paper, a simple and rapid method of evaluating galvanized steel sheet corrosion in a CuSO4 solution, as an experimentation proposal for corrosion teaching. Galvanized steel corrosion is present in tanks and tubing by leading of natural or industrial waters which contain soluble copper compounds. This was the rationale for choosing the Cu2+ ions solution as an oxidizing agent. The method principle is based on visual colorimetry because the used oxidant has an intense blue color. Thus, a change in its concentration as a result of the corrosive process can be followed by a color intensity change in the solution thereby allowing evaluation of the corrosion rate.

A problematização das atividades experimentais na educação superior em Química: uma pesquisa com produções textuais docentes - parte II

Through the analysis of articles with proposals for experimental activities and with current pedagogical, epistemological and environmental discussion on experimentation by Chemistry professors, this paper investigates ways of highlighting relevant methodological characteristics that can be incorporated in experiments. 102 articles from national periodicals were analysed, all of which suggested experiments for use in Chemistry higher education. Based on analysis of the suggestions for experiments it appears that of particular importance are: visions, such as those that explain a belief that experimentation incentivizes motivation and conceptual learning; awareness of observation influenced by empiricism; and "errors" of students, which enrich their knowledge.

Análise vibracional de compostos de coordenação de niquel(II): uma abordagem ao ensino dos grupos pontuais

This paper presents an IR and Raman experiment executed during the teaching of the course "Chemical Bonds" for undergraduated students of Science and Technology and Chemistry at the Federal University of ABC, in order to facilitate and encourage the teaching and learning of group theory. Some key aspects of this theory are also outlined. We believe that student learning was more significant with the introduction of this experiment, because there was an increase in the discussions level and in the performance during evaluations. This work also proposes a multidisciplinary approach to include the use of quantum chemistry tools.

A brief introduction to molecular orbital theory of simple polyatomic molecules for undergraduate chemistry students

A simple, four-step method for better introducing undergraduate students to the fundamentals of molecular orbital (MO) theory of the polyatomic molecules H2O, NH3, BH3 and SiH4 using group theory is reported. These molecules serve to illustrate the concept of ligand group orbitals (LGOs) and subsequent construction of MO energy diagrams on the basis of molecular symmetry requirements.

Sintonização de estados quânticos: um estudo numérico do oscilador harmônico quântico

The quantum harmonic oscillator is described by the Hermite equation.¹ The asymptotic solution is predominantly used to obtain its analytical solutions. Wave functions (solutions) are quadratically integrable if taken as the product of the convergent asymptotic solution (Gaussian function) and Hermite polynomial,¹ whose degree provides the associated quantum number. Solving it numerically, quantization is observed when a control real variable is "tuned" to integer values. This can be interpreted by graphical reading of Y(x) and |Y(x)|², without other mathematical analysis, and prove useful for teaching fundamentals of quantum chemistry to undergraduates.

Novas métricas holísticas para avaliação da verdura de reações de síntese em laboratório

New semi-quantitative metrics for simple evaluation of global greenness of chemical reactions used in teaching laboratories, namely, the Green Circle (GC) and Green Matrix (GM), were developed. These metrics globally consider all Twelve Principles of Green Chemistry. To illustrate their construction, the greenness of several syntheses performed in the laboratory under different sets of conditions was assessed. The tools were validated by comparing the results with another metric, the Green Star (GS), developed in our previous study. Results showed these new metrics were useful for the intended purpose, having the advantage of being simpler than the GS.

Tropical biodiversity: has it been a potential source of secondary metabolites useful for medicinal chemistry?

The use of natural products has definitely been the most successful strategy in the discovery of novel medicines. Secondary metabolites from terrestrial and marine organisms have found considerable use in the treatment of numerous diseases and have been considered lead molecules both in their natural form and as templates for medicinal chemistry. This paper seeks to show the great value of secondary metabolites and emphasize the rich chemical diversity of Brazilian biodiversity. This natural chemical library remains understudied, but can be a useful source of new secondary metabolites with potential application as templates for drug discovery.

Un método para enseñar el porqué suceden las reacciones químicas

A methodology is proposed for explaining one of the central questions in the teaching of general chemistry courses to freshman students: why do chemical transformations occur? The answer to this question is based on thermodynamics but we propose arriving at an answer in a more intuitive way by using computational tools in a bid to increase the motivation of students for learning chemistry.

Visual demonstration of the ionic strength effect in the classroom: the Debye-Hückel limiting law

The effects of ionic strength on ions in aqueous solutions are quite relevant, especially for biochemical systems, in which proteins and amino acids are involved. The teaching of this topic and more specifically, the Debye-Hückel limiting law, is central in chemistry undergraduate courses. In this work, we present a description of an experimental procedure based on the color change of aqueous solutions of bromocresol green (BCG), driven by addition of electrolyte. The contribution of charge product (z+|z-|) to the Debye-Hückel limiting law is demonstrated when the effects of NaCl and Na2SO4 on the color of BCG solutions are compared.

Avaliação do conhecimento sobre periodicidade química em uma turma de química geral do ensino a distância

This work describes the software Quiptabela, suggests a teaching activity, and analyses responses of general chemistry students from the Biological Sciences distance course at the Federal University of Tocantins. The software was described according to its educational potential, featuring the creation of dozens of charts or tables correlating physicochemical properties of the elements, being Brazilian, and free distribution. The teaching activities suggested analyzed students' ability to create and analyze tables and charts correlating the properties of chemical elements. Some 41% of students tested could define the term "periodic", but failed to use the concept to explain and differentiate changes in mass or atomic radius with the atomic number of elements.

A abordagem de questões ambientais: contribuições de formadores de professores de componentes curriculares da área de ensino de química

This paper presents the results of a study involving current teachers of the chemistry teaching curricular components of twelve Chemistry licentiate courses at state universities in the South and South-east of Brazil. The aim was to analyse how these curricular components can work together to address environmental issues in Chemistry teacher-training. From analysis of the interviews, it can be ascertained for example that environmental themes in the curricular components analysed are treated with differing levels of intensity and perspectives, and in some cases, have a more illustrative character regarding chemistry concepts.

Estudo das relações entre estrutura e atividade de parabenos: uma aula prática

Parabens are p-hydroxybenzoic acid esters widely used as preservatives. With the aim of teaching the structure-activity relationships (SAR) knowledge in a practical form, this paper proposed a practical class to view the SAR of parabens as antimicrobial agents. Methyl, ethyl, n-propyl, isopropyl and isopentyl paraben compounds were synthesized and their respective antimicrobial activities were assessed through determination of minimum inhibitory concentrations (MIC) against Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922 stains. With the MIC values, it was possible to verify theircorrelation with calculated lipophilicity (ClogP). This method can be applied in practical Medicinal Chemistry classes.

Metodologia de ensino jigsaw em disciplina de química medicinal

In this paper, we describe an educational experience involving the use of the jigsaw method on the Medicinal Chemistry course at the University of São Paulo, Brazil. The goal of this proposal was to investigate acceptance and contributions of the method to undergraduate chemistry teaching. Feedback on the jigsaw method collected from the focus groups and questionnaires showed that participants generally acknowledged the advantages of the jigsaw method in helping them learn the Medicinal Chemistry subject. Suggestions for improving the jigsaw method were also received from participants.