Abstract
This study unveils a new transition state (TS) leading to the acyclic product via synchronous double proton transfer by automatedly exploring the potential energy surface of β -D-xylopyranose under pyrolysis conditions. Quantum chemistry methods with multi-path canonical variational transition state theory show that the standard activation enthalpy of the new TS (44.9 kcal mol-1 ) is 1.5 kcal mol-1 lower than that of the well-established channel; however, the latter's rate constant ( 4.36 × 10-2 - 9.96 × 101 s-1 ) is higher in the 673.15-873.15 K pyrolytic range by a factor of 5-8. This gap narrows to a factor of 2 within 320-400 K, signifying that the new TS can potentially impact the acyclic product production in this low-temperature regime. This is particularly relevant for β -D-xylopyranose trimers, as the interior unit bears different substituents at the C1 and C3 positions.