A common question in chemistry is that of regioselectivity: “where will my molecule react?” This is an important problem in many fields:
Unfortunately, regioselectivity is also very difficult to predict. In theory, one could predict the regioselectivity of a given chemical process by modeling each transition state at an accurate level of theory and then comparing the various barrier heights to generate a prediction for the rates of various processes. In practice, however, finding the necessary transition states is tedious and difficult to automate, making the amount of human and computer time necessary for accurate kinetic modeling impractical.
This approach also requires a precise atomistic understanding of the various pathways in question—selectivity depends on the molecularity and conformation of the various transition states, which makes it difficult to apply in cases where the precise reacting partner might not be known ahead of time (e.g. non-specific material decomposition).
Fukui indices, named after Kenichi Fukui (the 1981 Nobel Laureate in Chemistry), quantify how a molecule’s electron distribution changes upon adding or removing an electron. Computing Fukui indices gives an atom-centered depiction of where a molecule will localize additional positive or negative charge, which in turn can be used to predict potential sites of downstream reactivity. In practice, Fukui indices have been shown to be useful in predicting drug metabolism, site selectivity in organic reactions, and more.
There are three different Fukui indices—f(+), f(-), and f(0)—each of which predicts a different mode of reactivity. f(+) tells you where a molecule will react with nucleophiles, f(-) tells you where a molecule will react with electrophiles, and f(0) tells you where a molecule will react with radicals.
Importantly, Fukui indices are a ground-state property, so they're fast to compute and don't require computation of transition states or even identification of the reacting partner, thus bypassing the issues discussed above.
Rowan makes the submission, computational, and analysis of Fukui indices fast and intuitive; with Rowan's Fukui index workflow, scientists can quickly gain valuable insights about the stability and reactivity of their molecules within seconds. Our software automatically runs the entire sequence of optimizations and single-point calculations needed to compute Fukui indices and displays the output as publication-quality figures right in your browser. Here's one such calculation, which took less than four seconds to run through Rowan's cloud infrastructure:
Rowan automatically calculates all three Fukui indices; to toggle between different views, simply select the appropriate top-level tab. The cutoff for visualization can be changed by adjusting the slider at the bottom of the screen.
