Ab Initio Study Toward The Effect of Electron Withdrawing­ Group on Alpha Carbon Substituent of Styrene in Rhodium­ Catalyzed Hydroformylation Reaction

• Main Author: Wibowo, Reksy
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/37968
• Institution: Institut Teknologi Bandung

Computational studies of the hydroformylation reaction of styrene contammg carboxamido as electron-withdrawing group at the alpha carbon substituent was done using the Hartree-Fock level of theory and LANL2DZ basis set for Rhodium and 6-31G basis set for atom other than rhodium. Computational results indicate that the reaction pathway for the formation of linear aldehydes energetically preferable than branched aldehydes. Studies on the carbonyl insertion step illustrates the possibilities for an explanation of the regioselectivity preferences to a linear aldehyde, with a value of L1G for linear aldehydes is -45,80 kJ I mol and Gibbs energy activation of 85,40 kJ I mol, while for branched aldehydes, the value of L1G and gibbs energy activation are 34,64 kJ I mol and 116,36 kJimol, respectively. However, at the step of acyl hydrogenolysis, L1G value for linear and branched aldehydes are 24,24 kJ I mol and -50,89 kJ/mol respectively, which indicates that this step may contribute to determine the reaction regioselectivity. Thermodynamic studies was carried out by replacing the phenyl group substituent on carboxamido with CF3 and CF2Cl shows that the stronger the effect of electron-withdrawing group, reaction was thermodynamically preferred on the branch aldehyde reaction pathway than linear aldehydes pahtway. The influence of the strength of the electron-withdrawing group electronically affect alkene insertion step, carbonyl insertion and acyl hydrogenolysis step. At the first two, linear aldehyde reaction pathway still thermodynamically more stable than the branched aldehydes but with diminishing value of MG as the strength of the electron -withdrawing group increase. However, at acyl hydrogenolysis step, increasing the strength of electron withdrawing groups make thermodynamically less favorable for aldehydes linear pathway and proportional to the increase of L1L1G value at this step.