ABSTRACT
I. Introduction ...................................................................................................................... 417
II. Isotope Effects with Short-Lived Radionuclides............................................................. 418
A. Fluorine Kinetic Isotope Effects .............................................................................. 418
B. Carbon Kinetic Isotope Effects................................................................................ 418
III. Synthesis of Compounds Labelled with Short-Lived Radionuclides ............................. 419
A. Labelling with
C ................................................................................................... 419
B. Labelling with
F.................................................................................................... 419
IV. Kinetic Methods — A Combination of Liquid Chromatography
and Liquid Scintillation ................................................................................................... 420
V. Determination of Rate-Limiting Steps ............................................................................ 421
A. Using Leaving Group F KIEs — Nucleophilic Aromatic Substitution.................. 421
1. The Effect of Solvent on the Rate-Limiting Step............................................. 422
2. The Effect of Steric Hindrance on the Rate-Limiting Step.............................. 422
B. Concerted or Stepwise Reaction? The Use of F KIEs and Double Labelling
for a Base-Promoted Elimination ............................................................................ 422
VI. Probing Transition-State Structure — Nucleophilic Aliphatic Substitution .................. 423
A. Relative Carbon KIEs .............................................................................................. 423
B. Labelled Central atom: Probing Steric Effects........................................................ 424
C. Labelled Nucleophile ............................................................................................... 425
1. The Effect of Substitution in the Substrate....................................................... 425
2. The Effect of Substitution in the Leaving Group............................................. 426
VII. The Determination of Secondary Deuterium KIEs by the Aid of Radioactive Carbon... 426
VIII. Secondary Carbon KIE in a Proton-Transfer Reaction................................................... 427
IX. Carbon Isotope Effects for Enzyme-Catalysed Reactions .............................................. 428
Acknowledgments ........................................................................................................................ 428
References..................................................................................................................................... 428
This chapter describes the use of the short-lived radionuclides
C and
F in the study of reaction
mechanisms.
