STUDY AB INITIO OF CARBONYLATIVE REACTION MECHANISM OF ALLYL ALCOHOL CATALYZED
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 u...
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| Format: | Theses |
| Language: | Indonesia |
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| Online Access: | https://digilib.itb.ac.id/gdl/view/32572 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | 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. |
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