# Xylopyranose Ring‐Opening by Single and Double Proton Transfers Under Pyrolysis Conditions

## TL;DR

The paper discovers a new chemical pathway for breaking down xylopyranose rings under heat, which could improve biomass conversion processes.

## Contribution

A novel transition state for xylopyranose ring-opening is identified, offering new insights into hemicellulose pyrolysis mechanisms.

## Key findings

- A new transition state with lower activation enthalpy is found but has a slower rate at higher pyrolysis temperatures.
- The new pathway becomes more relevant at lower temperatures (320–400 K), impacting acyclic product formation.
- The discovery informs kinetic models for biomass conversion and hemicellulose pyrolysis.

## 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.

Using automated reaction discovery tools, quantum chemistry, and kinetic modeling, we identify and characterize a novel transition state for xylopyranose ring opening reaction. This finding enhances the molecular‐level understanding of hemicellulose pyrolysis, providing new insight into reaction pathways relevant to biomass conversion and informing kinetic models for engineering applications.