We recently proposed a new physical organic chemistry direction. It examines how structure affects the 1° isotope dependence of 2° KIEs in H-transfer reactions and how this dependence provides information about the structure of the tunneling ready states (TRSs). Our hypothesis is that H- and D-tunneling have TRS structures which have different donor-acceptor distances (DADs), and pronounced 1° isotope effect on 2° KIEs should be observed in tunneling systems that are sterically hindered. Since 1° H-tunneling possesses longer DAD than 1° D-tunneling, the study of the 1° isotope effect on 2° KIEs becomes that of the DAD effect on 2° KIEs. The hypothesis becomes “pronounced DAD effect on 2° KIEs should be observed in sterically hindered systems, and the shorter the DAD, the greater the steric effects, the lower the 2° KIE.” This can be studied using the computation methods. I investigated this hypothesis by calculating the DAD effect on 2° KIEs at different positions in two hydride transfer systems. The signs of the 2° KIEs and the DAD (in)dependence of the 2° KIEs were discussed. The experimental results were attempted to fit to the calculations to find the TRS structures.
|Commitee:||Jones, Myron W., Khazaeli, Sadegh|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 55/03M(E), Masters Abstracts International|
|Keywords:||Donor-acceptor distance, H-tunneling, Hydride transfer reactions, Kinetic isotope effect|
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