AB INITIO COMPUTATIONAL STUDY ON AROMATICITY OF PYRROLE, FURAN AND TIOPHENE RADICAL BY HARTREE FOCK METHOD

• Main Author: Hendra Saputera, Wibawa
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/34859
• Institution: Institut Teknologi Bandung

Computational study is used to determine aromaticity in radical compounds of furan, pyrrole and tiophene. These calculations are supported by GAMESS (General Atomic Molecular Electronic Structure System) program. In these research, some properties of the radicals such as molecular geometry optimization in ground states and excited states, and Aromaticity Stabilization Energy (ASE) of each radical compounds will be determined. Those aspects will be determined with Unrestricted Hartree Fock (UHF) method, Becke-3 Lee-Yang-Par (B3LYP) as the type of Density Functional Theory (DFT), and 6-311G as basis sets. After the most stable radical in each radical compounds are found, single point calculations to calculate total energy in excited state are accomplished by Restricted Hartree Fock (RHF) method and Time Dependent Density Functional Theory (TDDFT) as the type of DFT. On the other hand, ASE in each most stable radical is calculated to know stabilization of resonance in aromatic system. These calculations show that radical state in each carbon of compounds cause fluctuation energy in aromatic system and if ASE value in three radical compounds are compared, from the lowest ASE value or most stable radical compound is tiophene, pyrrole, and furan. It can be explained theoritically when netral compound is changed to radical compound, single electron in radical move from equatorial position to axial position, change the electron ? in aromatic system so total electron in aromatic system become fewer. However, this case can be revealed with visualization of radical in aromatic system.