Interacting Quantum Atoms Analysis of the Reaction Force: A Tool to Analyze Driving and Retarding Forces in Chemical Reactions

Abstract

The analysis of the reaction force and its topology has provided a wide range of fruitful concepts in the theory of chemical reactivity over the years, allowing to identify chemically relevant regions along a reaction profile. The reaction force (RF), a projection of the Hellmann-Feynman forces acting on the nuclei of a molecular system onto a suitable reaction coordinate, is partitioned using the interacting quantum atoms approach (IQA). The exact IQA molecular energy decomposition is now shown to open a unique window to identify and quantify the chemical entities that drive or retard a chemical reaction. The RF/IQA coupling offers an extraordinarily detailed view of the type and number of elementary processes that take reactants into products, as tested on two sets of simple reactions.

Atoms in molecules in real space: a fertile field for chemical bonding

“…Thus, the IQA decomposition of F ( ξ ) into self-atomic/group components and classical/exchange–correlation interaction terms, which can be obtained through differentiation of cubic splines, yields chemically appealing images in terms of bonds, covalency and ionicity for different types of reactions. 160,161 Similar descriptions can be obtained with the closely-related Reduced Energy Gradient (REG) technique, 162 which relates the gradient of selected IQA components to the gradient of the total energy with respect to an arbitrary reaction coordinate for binding or reactive processes.…”

A deeper analysis of the role of synchronicity on the Bell–Evans–Polanyi plot in multibond chemical reactions: a path-dependent reaction force constant

“…This definition of DE act has allowed analysing the effect of a given substituent, 17 solvent [29][30][31] or catalyst 32,33 by inspecting changes in both energetic components. The F(x)-based analysis has been coupled to the activation strain model [34][35][36] and the interacting quantum atoms 37,38 to gain additional insights into the physical phenomena governing each reactive region.…”

The increased Diels–Alder reactivity of umpolung tropone: analysis of individual atoms and bonds using QTAIM and IQA along complete IRC paths

“…13 Even though the IQA@IRC protocol might seem challenging, considering the computational cost needed, the results it yields more than compensate the computation effort employed in the analysis, 14 as can be seen from the increasing number of studies reporting various kinds of IQA-based analysis applied to reactivity mechanisms. [15][16][17][18][19] F I G U R E 1 Scheme for the Diels-Alder (DA) reactions studied in this work, featuring maleimide (M) as the dienophile and the five different dienes: tropone (1) and the umpolung derivatives 2prot, 2, 3prot, and 3. The blue dashed lines represent the new σ bonds being formed, whereas the red curved arrows represent the standard DA approach found in most introductory textbooks.…”

“…This methodology was implemented and fully automatized recently 13 . Even though the IQA@IRC protocol might seem challenging, considering the computational cost needed, the results it yields more than compensate the computation effort employed in the analysis, 14 as can be seen from the increasing number of studies reporting various kinds of IQA‐based analysis applied to reactivity mechanisms 15–19 …”