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Published on: December 4, 2017
Redox potential inversion by ionic hydrogen bonding between phenylenediamines and pyridines.
Yi-Chun Chung1, Yi-Jung Tu, Shih-Hua Lu
1Department of Applied Chemistry, National Chi Nan University, Puli, Nantou, Taiwan.
Organic Letters
|May 4, 2011
Summary
Hydrogen bonding affects phenylenediamine oxidation potentials. The study reveals a linear relationship with pyridine basicity and different patterns with alcohols, impacting electrochemical analysis.
Area of Science:
- Electrochemistry
- Physical Chemistry
- Organic Chemistry
Background:
- Phenylenediamines (PD) are electrochemically active compounds.
- Hydrogen bonding interactions can significantly influence redox potentials.
- Understanding these interactions is crucial for controlling electrochemical reactions.
Purpose of the Study:
- To investigate the effect of hydrogen bonding on the second oxidation potential of phenylenediamines (PD).
- To explore the relationship between pyridine basicity and potential shifts in PD oxidation.
- To compare the hydrogen bonding interactions of oxidized PD with pyridines and alcohols.
Main Methods:
- Electrochemical oxidation of phenylenediamines.
- Cyclic voltammetry to measure oxidation potentials.
- Analysis of potential shifts in relation to pK(a) of pyridines and alcohol structures.
Main Results:
- The second oxidation potential of PD varies due to hydrogen-bonding formation between PD radical cations (PD(+•)) and pyridines.
- A linear relationship was observed between the potential shift and the pK(a) of protonated pyridines.
- Potential inversion was observed under certain conditions.
- Oxidized PD (PD(+•)) also forms hydrogen bonds with alcohols, but with a different potential shift pattern.
Conclusions:
- Hydrogen bonding is a key factor modulating the electrochemical behavior of phenylenediamines.
- The basicity of pyridine significantly influences the stability of the PD radical cation through hydrogen bonding.
- Alcohols interact differently with the PD radical cation, suggesting varied hydrogen bonding strengths or geometries.
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