STUDY COMPUTATION OF SIMPLE CHEMICAL REACTIONS AND VISUALIZATION FOR LEARNING CHEMICAL

• Main Author: Ridwan
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/32311
• Institution: Institut Teknologi Bandung

Chemistry lesson requires imagination of the behavior at the very small atomic level. This make it difficult to learn and to make students interested. Therefore, teachers need to find solution to overcome that problem using existing facilities, as well as to create a meaningful, fun, creative, dynamic and dialogical learning atmosphere. Computer can be used as a learning media that can help teachers to develop and achieve expected competences. Computer can visualize chemical reactions, determine molecular properties and molecular structure through computational chemistry calculations. Computational studies of chemical reactions, especially at the level of Senior High School (SMA) can help students to understand chemistry lessons. This study aims to create a learning media about chemical reactions, which will be built upon the results of computational study of simple chemical reactions, and their visualization. The selected chemical reactions are substitution, elimination, addition, and esterification reactions. Calcutions were done by computational methods quantum-mechanically, at the Hartree-Fock level of theory and 6-31G basis set. The calcutions of structural parameters, energy, and some chemical properties were performed on each molecule involved, either as reactant, transition state and products.Visualizations were performed by Jmol, i.e. a software that can show images of the structure of reactants and products, and also parameters of molecular structure such as bond lengths, bond angles and dihedral angles. The structure of reactants and products can be used to estimate the transition state structure that will be used to calculate the structure and energy of the transition state. The understanding of the reaction can be obtained from all these calculations. Then, the 3D structure of reactants, transition states, and products were created as a basis for the development of instructional media in the learning of chemical reaction for high school chemistry. The geometry optimization results for the substitution reaction: CH3CH2Cl + CH3OH ? HCl + CH3CH2OCH3, is = 22,79 kJ / mol and for (CH3)3CBr + H2O ?(CH3)3COH + HBr, is +49,06 kJ/mol. For the elimination reaction: (CH3)2CHBr+CH3CH2ONa ? CH2 = CHCH3 + NaBr, the reaction energy is - 89,48 kJ/mol and for (CH3)3CBr + H2O ? CH2 = C(CH3)2 + H2O + HBr, is +191,26 kJ/mol. For addition reactions: CH3CH = CHCH3+ Br2 ?CH3CHBr-CHBrCH3, the reaction energy is -116,52 kJ/mol. Lastly, for the esterification reaction: CH3COOH + CH3CH2OH ? H2O + CH3COOCH2CH3, the reaction energy is 34,23 kJ/mol. For the development of instructional media, the visualization of all the above calculated structures are mostly required, part of which are displayed as three-dimensional images, and others are used as the basis for creating animated reaction mechanisms with three-dimensional view.