STUDY AB INITIO OF CARBONYLATIVE REACTION MECHANISM OF ALLYL ALCOHOL CATALYZED

• Main Author: Setiadji, Soni
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/32572
• Institution: Institut Teknologi Bandung

Computational study to predict a carbonylative reaction mechanism of allyl alcohol catalyzed HCo(CO)4 complex into poly-4-hydroxybutyrate has been investigated. The calculation is performed to obtain structure optimized and activation energy of each reactions in the mechanism. This calculations using B3LYP/cc-pVDZ density functional theory with Gaussian 09 program for all atoms. The proposed mechanism involves five elementary steps: formation of active catalyst HCo(CO)3, coordination of allyl alcohol into HCo(CO)3, insertion of ally alcohol C=C bond toward Co-H bond, carbonylation, and esterification. In addition, formation of ?-butyrolactone as by-product was investigated. From calculation showed that the highest activation energy occurs when the formation of active catalyst HCo(CO)3 via CO dissociation from catalyst HCo(CO)4 was 129.65 kJ/mol. A reaction part of allyl alcohol coordination, which orientation of ally alcohol C=C bond parallel to the Co-H bond, determine the regioselectivity of resulted polymer, i.e., straight or branched chain polymers. Transition state of insertion-1,2 allyl alcohol has lower energy of 2.43 kJ/ mol compared to insertion-2,1. In mechanism, an activation energy of insertion-1,2 allyl alcohol is 10.04 kJ/mol, whereas insertion-2,1 is 15.48 kJ/mol. Carbonylation via alkyl migration into the equatorial CO ligands will produce acyl complex, which has an agostic interaction between Co with ?-H of carbonyl. This activation energy of carbonylation is 22.2 kJ/mol. Rearrangement of these carbonylation structure will produce a complex with interaction between Co with oxygen from C=O, which has energy 17.88 kJ/mol lower. The presence of C=O group in the acyl complex, allowing for the next reactions ,i.e., esterification and cyclecarbonylation. Cycle-carbonylation has energy of 29.24 kJ/mol lower than esterification. Activation energy from esterification is 98.86 kJ/mol, whereas activation energy from cycle-carbonylation is 63.29 kJ/mol. From energy level of mechanism indicates that carbonylative reaction of allyl alcohol catalyzed HCo(CO)4 is preferred to formation of ?-butyrolactone.