Vol. 104 No. 2 (2008)
Molecular Modelling has become so functional that nowadays is generally utilized for the study of chemical reactivity and homogeneous catalysis. This is mainly due to both the increase in the computational power and the fact that computational chemists are now able to undertake practical studies for experimental chemists. The analysis at molecular level of the reactivity is its major advantage. This article performs a general description of the main features of molecular modelling in homogeneous catalysis.
Ordered mesoporous materials are widely used both as catalyst or support. In the present work, the role of various structural and chemical parameters in the immobilization capacity of Candida antartica B (CaLB) enzyme on OMM (Ordered Mesoporous Materials) was studied. Two types of porous structures were prepared: cylinder (SBA-15, KIT-6) and cage (SBA-16, FDU-12) type. Additionally, each material was synthesized in pure silica and methyl functionalized forms. Finally, the resulting catalysts were evaluated for the tributyrin hydrolysis reaction, and the leaching of enzyme in aqueous media was tested.
Palladium-catalyzed cross-coupling reactions are fundamental organometallic transformations and nowadays have become a principal method of forming carbon-carbon and carbon-heteroatom bonds. In this report, essential features of cross-coupling reactions are review, mainly focused in the less developed C-S bond forming process. In addition, the results obtained in the coupling of aryl halides with aliphatic and aromatic thiols using a catalyst system derived from the bisphosphine Josiphos CyPFtBu ligand are presented.
The study of the metallurgical evolution of different chemical elements related to the manufacture of poured castings provides an useful tool in order to avoid the appearance of gas porosities. The formation of these defects into the metallic material has a critical influence on the technological properties of the obtained castings and affects to their functionality. This work analyses the most important types of gas porosities normally found in graphitic iron, aluminium and steel. In addition, the most apparent causes for these defects formation are discussed according to the physical and chemical processes which take place inside the melt.
Pollution by heavy metals is one of the most serious environmental problems today. Biosorption, by means of biomaterials such as marine seaweeds, mushrooms, bacteria and yeast, is considered a viable and applicable biotechnology for the large-scale treatment of residual waters with low heavy metals concentration in the range of 1 to 100 mg/L. Among the biosorbents used in this field, marine seaweeds have shown a higher efficiency, applicability, and selectivity for heavy metals than their analogs. The chemical and mechanical properties of marine seaweeds that show higher affinity with mainly divalent heavy metals; the comparison of biosorption by marine seaweeds and other biomaterials and finally the most prevalent techniques used in biosorbent's characterization and biosorption are detailed in the present review.
Mitigation of climate warming depends on the control of CO2 in the atmosphere. Generation of CO2 is mainly due to the production of energy from fossil fuels and can be minimized by reduction of energy consumption, higher efficiency in the use of fossil fuels and by shifting to renewable energy sources. Chemistry can contribute significantly to these strategies, especially for the development of renewable sources.
A pilot experience of teaching innovation on the EEES framework is being developed at the Faculty of Chemistry (University of Valencia) since 2003−2004 academic year. One of the main objectives has been to design collaborative activities based on active methodologies, in which the student becomes the centre of the learning process. Among them, the most enriched and, probably, best valued by the first-year students, is the teamwork designed with a "mini-symposium" format, that is, with oral and poster presentations. Here, we present the evolution and results of this activity from the beginning until its present format.
The amorphous alloys, or bulk metallic glasses, are a mixture of several metals that when they are rapidly quenched present similar characteristics to the plastics but higher tensile strengh. This alloy allows the teacher to show the relationships between the new technologies and the scientific progress, the atomic structure and the physical properties, and finally, the new properties of the materials and their novel application provide such important benefits in numerous fields, among them, leisure and sports.
This paper offers a guide on the history of chemistry. It is made of two closely related parts. The first one (published in a former issue of this journal) describes the development of history of chemistry as an academic discipline from its origins until the twentieth century. This second part offers the main sources of information (encyclopaedias, textbooks, journals, etc) and the characteristics of the most outstanding European teaching and research institutions on history of chemistry, relying on a survey recently carried out by the Historical Group of EuCheMs. Additional information is offered in http://www.uv.es/bertomeu.