چکیده :
The study of the kinetics and mechanisms of the gas-phase thermal decarboxylation of allyl formate and
2-methylallyl formate was carried out by means of electronic structure calculations using Density Functional
Theory (DFT) functionals: B3LYP, B3PW91, MPW1PW91 and PBEPBE. Two possible molecular
mechanisms were investigated: a concerted [1, 5] hydrogen shift through a six-centered cyclic transition
state, and a [1, 3] hydrogen shift mechanism through a four-centered cyclic transition state. Calculation
results suggest these reactions to be unimolecular and proceed in a concerted mechanism through a sixmembered
cyclic transition state (TS) geometry. Despite the similar activation energies, differences were
found when comparing the two elimination processes. In the case of allyl formate, the reaction shows
small predominance of the change in the terminal allyl moiety bond order and the CAOester bond breaking.
Conversely, for 2-methylallyl formate, the process is highly controlled by the new C@O double bond
development leading to carbon dioxide formation. Moreover, in the 2-methylallyl formate decomposition,
the a-carbonyl hydrogen transfer to the terminal allyl carbon to produce 2-methyl propene is at
a very early stage in the TS compared to allyl formate.
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