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Generation of a cyclopentenyl cation labelled with a single deuterium at C‐4. Rate studies of the scrambling reaction
Author(s) -
Brunelle Patrick,
Sorensen Ted S.,
Taeschler Christoph
Publication year - 2003
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.660
Subject(s) - chemistry , deuterium , scrambling , superacid , kinetics , activation energy , hydrogen–deuterium exchange , derivative (finance) , nuclear magnetic resonance spectroscopy , hydrogen , computational chemistry , stereochemistry , catalysis , organic chemistry , atomic physics , linguistics , philosophy , physics , quantum mechanics , financial economics , economics
The kinetics of the hydrogen scrambling reaction in the cyclopentenyl cation 1 were studied. The pure 4‐deutero derivative of 1 was prepared using superacid conditions and the activation energy Δ G ‡ for the rearrangement of this label to the C‐1(3) position of 1 was determined using low‐temperature 2 H NMR spectroscopy. In addition, the sequential rearrangement of the deuterium label from C‐4(5) → C‐1(3) → C‐2 was noted in a qualitative fashion. Based on a statistical analysis, the activation free energy Δ G ‡ for a single hydrogen (deuterium) migration leading to the 4‐cyclopentenyl cation intermediate was determined to be 18.3 kcal mol −1 (−20.8 °C), in good agreement with the less direct determination provided by an earlier NMR line‐broadening and spin‐saturation transfer experiment. Copyright © 2003 John Wiley & Sons, Ltd.