Search

Molecular models derived from results of quantum-chemical calculations present an important category of didactic instruments in chemistry education. These models can be used especially as tools for supporting the students’ understanding by visual learning, which can adequately address complexity of many chemical topics, incorporate appropriate didactic principles, as well as utilize the benefits brought up by the actual information technology. The proposed molecular models are non-trivial examples of didactic application of computational chemistry techniques in illustration of electron interactions in amidic group, namely the interaction of the free electron pair on the nitrogen atom with the carbonyl group and also the interaction of atoms in the amide group with other surrounding atoms in the molecule. By these molecular models it is possible to explain acid-base properties of amides applying knowledge of electron density distribution in the molecules and the resulting electrostatic potential. Presentation of the structure and properties of the amides within education is important also for the reason that amidic functions are involved in many important natural substances (e.g. proteins, peptides, nucleic acids or alkaloids), synthetic macromolecular substances (e.g. Silon) or pharmaceutical preparations (e.g. paracetamol). This paper investigated the effect of using different types of models while teaching organic chemistry on student understanding of new concepts and the spatial structure of new molecules, as well as preference of a particular model type and illustrates the possibilities of computer-assisted molecular modelling in supporting chemistry teaching and learning. Keywords: Molecular models, Acidity, Amides, Basicity, Electrostatic potential

A vast population of the world is vulnerable to fluoride contaminated drinking water intake, and there are various defluoridation techniques available to date as well. But the removal of fluoride is still a challenge, especially in remote rural areas because available techniques require proper supervision and equally, ineffective due to economic issues and electricity crisis. Among all methods of defluoridation, adsorption methods are found better to carry out at the community and household level but sometimes demanded a replacement of commercial activated carbon (CAC) due to economic issues and less availability in remote areas. Hence keeping this in mind, the present study assessed the pine cone activated carbon (PCAC) as adsorbent material in the defluoridation that is easy to prepare like any other agriculture-waste material. The activated carbon was prepared using KOH as an impregnating agent for activation of pine cone by pyrolysis technique at 800 °C and has been analyzed for various parameters in the fluoride removal viz. contact time, dose variation, pH and initial fluoride concentration. The maximum adsorption capacity of fluoride on pine cone activated carbon was found 1.34 mg/g of initial fluoride concentration (2–12 mg/L) at pH (6.8–7.0) with a contact period of 45 min. Also, a comparison has been made between Pine Cone Activated Carbon (PCAC) with Commercial Activated Carbon (CAC) based on obtained results. It has been suggested that Pine cone activated carbon is efficient as well as cheap adsorbent and can be used for the removal of fluoride from drinking water in rural areas.

A simple, reproducible and efficient reverse phase high performance liquid chromatographic method was developed for simultaneous estimation of etoricoxib and thiocolchicoside in combined tablet dosage form. Formulation containing etoricoxib and thiocolchicoside is used as analgesic. Chromatography was performed on a 250 mm x 4.6 mm, 5-microm particle size, BDS Hypersil C-18 column with trifluoroacetic acid buffer (pH 2.6) and acetonitrile (75:25, v/v) as a mobile phase. The detection of the combined dosage form was carried out at 220 nm and a flow rate employed was 1.5 mL/min. The retention times were 6.6 and 3.1 min for etoricoxib and thiocolchicoside, respectively. Linearity was obtained in the concentration range 20 to 160 ppm for etoricoxib and in the range 2 to 16 ppm for thiocolchicoside with a correlation coefficient of 0.9918 and 0.9994, respectively. The results of the analysis were validated statistically and recovery studies confirmed the accuracy and precision of the proposed method.