# Pre‐Activation as a Route for Tuning the Kinetics of Mechanochemical Transformations

## TL;DR

Pre-activating certain starting materials can significantly speed up mechanochemical reactions and affect their outcomes.

## Contribution

Selective pre-activation of reagents offers a new way to control mechanochemical reaction rates and polymorphic outcomes.

## Key findings

- Pre-activation of the most stable reagent increases reaction rates by up to 10-fold.
- Pre-activation of less stable reagents shows negligible kinetic enhancement.
- Polymorphic outcomes in mechano-co-crystallization are sensitive to pre-activation.

## Abstract

Learning to control reaction kinetics is essential for translating any chemical technology into real‐world application. Based on time‐resolved in situ powder X‐ray diffraction data, we demonstrate the opportunity to tune mechanochemical reaction rates through the pre‐activation of the starting reagents. For three model co‐crystal systems, the pre‐activation of the most stable reagent yields up to a ca 10‐fold increase in the reaction rate, whilst negligible kinetic enhancement is seen when the less stable reagent is pre‐activated. Moreover, we demonstrate how the polymorphic outcome of mechano‐co‐crystallization is also sensitive to pre‐activation of the starting material. Our results suggest that reproducibility of mechanochemical processes requires detailed understanding over the origin and history of reagent powders, whilst providing a new conceptual framework to design and control mechanochemical reactions.

The kinetics of mechanochemical reactions can be markedly altered through the selective pre‐activation of starting reagents, as revealed through reaction monitoring using time‐resolved in situ powder X‐ray diffraction and ab initio density functional theory simulation.