With support from the Organic Dynamics Program, Professor William H. Saunders, Jr. of The University of Rochester will study the effect on chemical behavior caused by replacing one or more atoms in a molecule with an isotope (an atom with the same qualitative chemical behavior but a different atomic weight). The difference in reaction rates caused by such replacements will lead to conclusions about the detailed pathways (mechanisms) of the particular chemical reactions in question. Such knowledge facilitates the use of the reactions to synthesize compounds of industrial and pharmaceutical interest. Major emphasis will be placed on exploring the influence of quantum mechanical tunneling on rates and isotope effects in proton transfer reactions. In order to obtain such information, isotope effects and their temperature dependencies will be determined for bimolecular eliminations and deprotonation of aliphatic nitro compounds. Another characteristic of tunneling that will be explored is noncumulative behavior of isotope effects in multiply labeled species (isotope effects on isotope effects). Kinetic enolate formation and other reactions showing attenuated temperature dependencies will be studied. Dr. Saunders will test the hypothesis that such abnormal temperature dependence can in many instances be attributed to reaction via more than one base species. Isotope effect calculations will be performed as they are needed to interpret experimental results.
