Quantitative determination of activation energies in mechanochemical reactions

Abstract

Mechanochemical reactions often result in 100% yields of single products, making purifying procedures obsolete. Mechanochemistry is also a sustainable and eco-friendly method. The ever increasing interest in this method is contrasted by a lack in mechanistic understanding of the mechanochemical reactivity and selectivity. Recent in situ investigations provided direct insight into formation pathways. However, the currently available theories do not predict temperature T as an influential factor. Here, we report the first determination of an apparent activation energy for a mechanochemical reaction. In a temperature-dependent in situ study the cocrystallisation of ibuprofen and nicotinamide was investigated as a model system. These experiments provide a pivotal step towards a comprehensive understanding of milling reaction mechanisms.

The effect of ball mass on the mechanochemical transformation of a single-component organic system: anhydrous caffeine

“…In the previous literature, it is generally suggested that the important factor of the milling ball is its mass [17] and that the rate of conversion is proportional to the energy imparted by the associated impact. This may be true for some reactions [55,56]. In the present case, ball bass may be associated with more rapid comminution and an increase in the generation of defects per impact.…”

Decoupling the Arrhenius equation via mechanochemistry

“…This difference in thermal energy is mainly due to how the ball mill is constructed, which can influence the environment of the mechanochemical reaction. 27 , 39 …”

Tandem In Situ Monitoring for Quantitative Assessment of Mechanochemical Reactions Involving Structurally Unknown Phases

“…In the kinetic assessment, one caveat should be kept in mind. Namely, the reaction mixture warms up during milling, which could influence the reaction kinetics as the reaction is occurring. Recently, we have shown that even mild temperature changes, achieved by preheating the milling assembly, can have a dramatic influence on the reaction kinetics and mechanism .…”

“…To remedy the currently very scarce mechanistic understanding of mechanochemical milling reactions, accumulation of knowledge of reaction profiles for a large number of reactions and reaction types will be required. Although Raman spectroscopy has been used to monitor mechanochemical reactions in situ and ex situ, current approaches mostly rely on extracting the reaction profile from changes in the intensity of a single peak . Clearly, continuing in this fashion would present a tedious task for collecting sufficient kinetic data for a variety of mechanochemical reactions conducted under a variety of reaction conditions.…”

“…AlthoughR aman spectroscopy has been used to monitor mechanochemical reactions in situ and ex situ, current approaches mostly rely on extracting the reaction profile from changes in the intensity of as ingle peak. [27,28] Clearly,c ontinuing in this fashion would presenta tedious task for collecting sufficient kinetic data for av ariety of mechanochemical reactions conducted underavariety of reaction conditions. Additionally,a ne xs itu approach is not suitable for self-propagating anda ir-sensitive reactions, as well as the use of volatile additives.…”