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Updated: Mar 9, 2026

Reductive Electropolymerization of a Vinyl-containing Poly-pyridyl Complex on Glassy Carbon and Fluorine-doped Tin Oxide Electrodes
Published on: January 30, 2015
Why Are Vinyl Cations Sluggish Electrophiles?
Peter A Byrne1, Shinjiro Kobayashi1, Ernst-Ulrich Würthwein2
1Department Chemie, Ludwig-Maximilians-Universität München , Butenandtstrasse 5-13, 81377 München, Germany.
Vinyl cations exhibit unique reactivity with nucleophiles, differing significantly from benzhydrylium ions due to high intrinsic barriers in their formation and reactions. This impacts their overall reaction rates and stability.
Area of Science:
- Organic Chemistry
- Physical Chemistry
- Reaction Kinetics
Background:
- Vinyl cations are transient intermediates in chemical reactions.
- Their reactivity patterns are crucial for understanding organic synthesis and reaction mechanisms.
- Comparison with diarylcarbenium ions provides insights into carbocation behavior.
Purpose of the Study:
- To determine the kinetics of vinyl cation reactions with various nucleophiles.
- To compare the reactivity of vinyl cations with diarylcarbenium ions.
- To investigate the origin of observed reactivity differences using computational methods.
Main Methods:
- Laser flash photolysis for generating vinyl cations.
- Photometric determination of reaction kinetics.
- High-level molecular orbital (MO) calculations.
Main Results:
- Vinyl cation reactivity order with nucleophiles mirrors that of benzhydrylium ions.
- Vinyl cation reaction rates are less sensitive to nucleophile variations compared to benzhydrylium ions.
- Vinyl cations react significantly slower than benzhydrylium ions with certain nucleophiles, despite slower ionization of their precursors.
Conclusions:
- High intrinsic barriers for sp2-sp rehybridization explain the slow formation and consumption of vinyl cations.
- The observed reactivity differences are attributed to these intrinsic barriers, not necessarily high intermediate energy.
- Understanding these barriers is key to explaining the kinetics of vinyl cation reactions.
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