Theoretical Chemistry
Theoretical chemistry is the study of chemical phenomena with the help of mathematical models and computer calculations. It is different from bench chemistry done in laboratories in that theoretical chemistry is done outside of the laboratory, and is done using supercomputers.
Most of theoretical chemistry is based on quantum mechanics. In fact, another name for theoretical chemistry is quantum chemistry. Theoretical chemists devise mathematical models to determine the properties of atoms and molecules, and to determine how atoms and molecules react with each other. These models are centered largely on quantum mechanical principles. Chemists perform numerically intense computations in order to make predictions from these models.
Though theoretical chemistry can be called chemistry out of the laboratory, there is a strong relationship between bench chemistry and theoretical chemistry. Theoretical chemistry allows chemists to study molecules that have not yet been isolated in a laboratory and molecules that are difficult to attain in the laboratory. It also allows chemists to study molecules without the fear of laboratory accidents and environmental hazards. The enormous advances made recently in computer technology allow computer modeling to be carried out for less cost than similar experimental work. Most importantly, theoretical work helps us better understand the behavior and properties of molecules. Theoretical chemistry and bench chemistry then have a strong, cooperative relationship.
There are limitations to what theoretical chemistry can do though. The accuracy of theoretical predictions is limited by the quality of the models. Although there is no reason to doubt the validity of quantum mechanics, the enormous complexity of Erwin Schrödinger's wave equation for molecules compels chemists to use many mathematical approximations. Chemists must always check these models against experimental results, and these models must be refined and redefined based on these experimental results.
Theoretical chemistry is not only concerned with the properties of atoms and molecules. It is also involved in examining reaction pathways, reaction mechanisms, and reaction rates. Additionally, theoretical chemists also work in the biochemistry field. Protein molecules are large biological polymers of small molecules called amino acids, and each protein has a unique amino-acid sequence. These molecules spontaneously fold and coil into a characteristic three-dimensional shape in solution. The shapes of these proteins is very important because the folding and coiling produces unique surface features, such as grooves and indentations. It is these features that determine how the protein functions and interacts with other molecules. But it is nearly impossible to learn the folding patterns of proteins in the laboratory or using pen and paper. Instead, computational chemistry is very useful in determining the folding patterns of proteins.
Computational chemistry is a branch of theoretical chemistry, which applies the basic equations of quantum mechanics to chemical systems. It can predict bond lengths in small molecules, vibrational frequencies, and binding energies to levels of accuracy comparable to experimental methods. Computational chemistry has a very practical application in drug design. Computer-aided drug design uses computational chemistry to determine which molecules may react with the active sites of bacteria and viruses. This process cuts down the cost of conducting many laboratory experiments to determine the same information. Drugs for Alzheimer's disease, hypertension, and AIDS have already been designed using computer-aided drug design.
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