Vol. 104 No. 3 (2008)

The concept of the "click" chemistry was introduced by Prof. Sharpless and coworkers in 2001 to define a modular synthetic approach that uses only the most practical and reliable chemical transformations. Among a number of reactions that meet these criteria, the Huisgen 1,3-dipolar cycloaddition of azides and alkynes, in particular the copper(I)-catalyzed version, has been established as the most effective and versatile. In the last years, its use has been spread exponentially in numerous applications within a variety of scientific fields including organic synthesis, molecular biology, and synthesis of new functional materials.

Keywords: "Click" chemistry, cycloaddition, azides, alkynes, 1,2,3-triazole

The aims of this work has been the development and application of analytical methodologies based on the combination of spectroscopic measures of ultraviolet with chemometric methods of experiments design to establishing the matrix of calibration and later analysis of the obtained results. Citric acid and tartaric acid have been the selected analytes for this study. Citric acid is a tricarboxylic organic acid that is present in most of the fruits, mainly in citruses like the lemon and the orange. Tartaric acid is an organic acid extended enough in the nature. It is in the grape, and in small amounts in cucumbers and potatoes. It appears in form of salt in some vegetables and their juices.

Keywords: citric acid, tartaric acid, experimental design, ANOVA, multiple lineal regression

The conjugate addition reaction is a widely employed tool for the synthesis of functionalized carbon chains. In this reaction several stereogenic centers can be formed at the α- and/or β-position of the activating group and stereochemical control can be achieved by introducing a chiral auxiliary linked to the conjugate acceptor or, alternatively, by employing a chiral catalyst. Regarding to the last topic, in the last years the use of chiral small organic molecules as catalysts (also referred to as organocatalysts) in several asymmetric transformations has been a field of intense research. In this paper, we present our main recent efforts directed toward the development of new asymmetric methodologies for carrying out conjugate addition reactions using chiral auxiliaries and organocatalysis.

Mitigation of climatic change requires controlling the amount of CO₂ in the atmosphere. Reduction of anthropogenic emissions of CO₂ can be the result of shorter production, or of its capture and storage when generated. Natural sinks of CO₂ of the natural carbon cycle constitute the most powerful system for the control of atmospheric CO₂. Good knowledge of their mechanisms is needed in order to design technologic and chemical contributions to increase their capacity.

The Sustainable Chemistry or Green Chemistry was born in the 90's of the twentieth century. Through their principles, chemists have been improving industrial production processes and designing new methodologies in laboratories to minimize the environmental impact of activities related to chemistry, as well as designing processes using renewable-raw materials and reducing the energy needed to carry them out. Through networks of various agencies and researchers, chemists have been combining to boost and developing technologies more respectful of the environment.

TThis paper summarizes ideas about the active learning of Chemistry. This concept, which has been the object of debate for many decades at pre-university levels, has been extensively discussed since the beginning of this century for the university level in European countries, promoted by the renowned "Bologna Process". This paper summarizes the presentations that were the focus of an international conference of physical and chemical education specialists, held in Madrid in July 2007, on "Active learning in physics and chemistry". A product of this conference was the edition of a book of proceedings, including 58 works by 146 authors.

Keywords: chemical education, active learning, Bologna process

High School students show a great interest about experimental activities in Chemistry and Geology subjects, being growing crystals one of the most attractive for them. Not only does this paper propose different ways to obtain crystals but also many practical suggestions for students so they can prove by themselves the relationship between the growing environment and the crystals morphology.

The present paper is an educative innovation project and an experience of Chemistry which has been carried out by students of a high school. They have determined characteristic parameters of citrus fruits, such as acidity, sugars, vitamin C, formol index, percentage of juice and flesh. Moreover this experience has been useful for studying acids and bases, hydrolysis reactions, pH, redox processes and also for measuring the variation of juice potential with pH.

We are presenting in this article the historical evolution of some Organic Chemistry laboratory techniques, focusing main- ly in the ones used for the determination of the structure of molecules. We will finish with two historical examples like the structure of the penicillin and steroids.

The development of organic Chemistry and Biology in the second half of the 19th century was key to the origin of Biochemistry. Some French chemists such as Dumas, Laurent and Berthelot, and also the Germans Wöhler, Liebig and Kekulé contributed to it. The study of alcoholic fermentation was another landmark to the development of Biochemistry. In 1897 Eduard Büchner provided evidence that alcoholic fermentation was not inherent in life. He proved the ability of cell-free ferments to break down glucose.