Chemistry theoretical screening

Recommended testing procedures depend on the stage of development of the process as indicated in Table 1.1. During early developmental chemistry work, only small amounts of materials will be available. In many cases, only theoretical information from the literature or from calculations is readily available. Screening tests can be run to identify the reaction hazards. Also, data for pilot plant considerations can be obtained. 

The products of photochemical rearrangements are occasionally quite different from what one may intuitively expect and this creates difficulty in their identification. In such cases, computational chemistry is perhaps our only resort. Several possible structures can be screened computationally with rather little cost in terms of time, effort, and money. Unfortunately, computational chemistry cannot predict a priori the structure of the unknown. However, if a good match between theoretically derived and experimental IR spectrum is found, then this constitutes a strong case and often is taken as proof of identification. 

A correlation analysis is a powerful tool used widely in various fields of theoretical and experimental chemistry. Generally, such an analysis, based on a statistically representative mass of data, can lead to reliable relationships that allow us to predict or to estimate important characteristics of still unknown molecular systems or systems unstable for direct experimental measurements. First, this statement concerns structural, thermodynamic, kinetic, and spectroscopic properties. For example, despite the very complex nature of chemical screening in NMR, particularly for heavy nuclei, various incremental schemes accurately predict their chemical shifts, thus providing a structural analysis of new molecular systems. Relationships for the prediction of physical or chemical properties of compounds or even their physiological activity are also well known. 

Tlie ultimate test of new, theoretically motivated protocols for materials discovery is, of course, experimental. To motivate such experimentation, the effectiveness of these protocols is demonstrated by combinatorial chemistry experiments where the experimental screening step is replaced by hgures of merit returned by the random-phase volume model. The random phase volume model is not fundamental to the protocols it is introduced as a simple way to test, parameterize, and validate the various searching methods,... 

In the past 15 years, combined advances in computer technology and innovative algorithms development provided the possibility to perform complex computational operations in a reasonable time scale. Therefore these theoretical methods, when used together with modern experimental techniques (combinatorial chemistry and high-throughput screening), are now widely used. 

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