Foreword: Applied computational chemistry

K. N. Houk
Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095-1569, USA

This themed issue of Chemical Society Reviews is very timely, coming shortly after the Nobel Prize in Chemistry was awarded in 2013 to the three chemists who, it can be argued, launched the beginning of applications of computational methods to large systems. Between the 1920s establishment of quantum mechanics and the 1970s, there were major developments of quantum mechanical methods and computer programs as well as empirical force field programs. However, computers were primitive, and the only computer programs available were quite limited. Warshel, Levitt, and Karplus began to take on large systems related to real chemistry, especially the enzyme lysozyme as well as photoresponsive molecules. The calculations were still at a very approximate level, but the breakthrough was to take on large systems by combining quantum mechanics and molecular mechanics in one calculation.

Fast forward to today's world, where computers are at least 10 million times faster than in the 1970s, and several orders of magnitude more plentiful, as well. An abundance of wonderful computer programs and modern graphics are available, and all of these things have elevated applied computational chemistry to a status as one of the major fields of chemistry in the 21st century, a worthy subject of this themed issue.

The forté of applied computational chemistry is to understand chemistry and to predict promising directions that experimentalists can follow to make new discoveries. The impacts of computations on the understanding of mechanisms and selectivities, especially in the organometallic, biosynthetic, and materials fields, are well represented in this themed issue. Experimentalists often turn to computational chemists for help with understanding how their chemistry works or to predict how to overcome problems encountered experimentally. Computational chemists also undertake the development of conceptual models to understand factors controlling reactivity (e.g., the Activation Strain or Distortion/Interaction Model), the nature of transition states (e.g., aromaticity), or the general relationship of electron densities to reactivity, as in Conceptual Density Functional Theory. These, and the power of high accuracy calculations, are also demonstrated in this issue.

This themed issue represents the power of applied computational chemistry as a guide to understanding and a driver of new chemistry.

This journal is © The Royal Society of Chemistry 2014