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Using phenyl cations as probes for establishing electrophilicity-nucleophilicity relations
Valentina Dichiarante1, Maurizio Fagnoni, Angelo Albini
1Department of Organic Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy.
The Journal of Organic Chemistry
|January 19, 2008
Summary
N,N-Dimethyl-4-aminophenyl cation probes nucleophile reactivity. Its triplet state shows reduced dependence on nucleophilicity, suggesting modifications to Mayr
Area of Science:
- Organic Chemistry
- Physical Chemistry
Background:
- N,N-Dimethyl-4-aminophenyl cation serves as an electrophilic probe.
- Understanding nucleophile reactivity is crucial in chemical reactions.
Purpose of the Study:
- To determine the relative reactivity of nucleophiles using N,N-Dimethyl-4-aminophenyl cation.
- To investigate the selectivity of the cation's singlet and triplet states.
Main Methods:
- Utilized N,N-Dimethyl-4-aminophenyl cation as an electrophilic probe.
- Employed competition experiments to measure reaction rates with various nucleophiles.
- Applied Mayr's nucleophilicity parameter (N) and a modified equation for analysis.
Main Results:
- The singlet state (1 1) of the cation exhibited unselective reactivity across different nucleophiles.
- The triplet state (3 1) showed limited reactivity variation (2 orders of magnitude) with nucleophiles over a broad N range.
- A modified Mayr's equation (log k = s(E + eN) with e = 0.33) best described the data for amines and pi nucleophiles.
Conclusions:
- The triplet state's reduced dependence on nucleophilicity is attributed to its half-filled sigma orbital.
- Mayr's equation can be extended to diverse reactions with a modified scaling factor (e < 1) based on the electrophilic probe's electronic structure.
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