#TITLE_ALTERNATIVE#

• Main Author: AMALIA AFIYANTI (NIM: 90514002) , NUR
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/20366
• Institution: Institut Teknologi Bandung

Chalcones is one of the most abundant natural product. One type of chalcones compound found in the bark of the plant are Cryptocarya costata. Compounds that be isolated is 2,4-dihydroxy-3,5,6-methoxy chalcone. The structure of 2,4-dihydroxy-3,5,6-methoxy chalcone has some geometric isomers. Cis-trans phenomenon is commonly known in the field of organic chemistry, but still interesting to be developed as a teaching material in schools and universities. This study aims to assess the geometric isomers of these compounds in terms of thermodynamics and apply them in learning. Method to assess the stability and geometric isomers energy were calculated using computational chemistry. Calculations using Gaussian 09 with density functional theory, B3LYP method and basis set 6-311G. The three torque involving single and double bonds. The three torque, studied the structure and stability in the singlet state and a triplet. The result of the calculation of singlet structure, torque 1 has an activation energy of 9.537 kcal/mol, while torque 2 and 3 are 3.150 kcal/mol and 7.8777 kcal/mol respectively. From these results it can be concluded that the compound 2,4-dihydroxy-3,5,6methoxy chalcone requires higher energy for isomerization with torque rotation are first, third, and second. The three torque can also be known that the isomer ΔG of the first, second, and third is 5.560 kcal/mol, -2.9543 kcal/mol, and 0.1518 kcal/mol respectively. ΔH value for each isomer are 4.764 kcal / mol, -2.7127 kcal / mol, and 0.5377 kcal / mol. Similarly, the same tendency when the structure of the triplet state. Torque 1 has an activation energy is 11.0875 kcal/mol, while torque 2 and 3 are -0.1964 kcal/mol and 5.8058 kcal/mol. Then, ΔG values are -0.4800 kcal/mol, 2.9310 kcal/mol and -2.0400 kcal/mol, while ΔH for each isomer are -1.3673 kcal/mol, -3.1689 kcal/mol, and -1.9804 kcal/mol. The results of the study isomers geometric subsequently applied as teaching materials through eXeLearning with simpler molecules such as ethane and ethene.