Using voltammetry to analyse hydrogen bonding interactions of donors and acceptors in non-aqueous solvents
Tessensohn, Malcolm Eugene
Date of Issue2017-01-31
School of Physical and Mathematical Sciences
The electrochemical behavior of phenols, quinones and phenylenediamines in non-aqueous solvents is strongly influenced by hydrogen bonding interactions, especially to the trace water that is present in the solvents. Hence, it is recommended that voltammetric studies on electroactive hydrogen donors and hydrogen acceptors measure and report the moisture content of their working solutions to enable accurate comparisons and better understanding of the data. The voltammetry of quinones and phenylenediamines were used in hydrogen bonding analysis of several compounds. In the case of quinones, their electrochemical parameter ΔEQ = |EQ1 – EQ2| (where EQ1 was the first reduction potential and EQ2 was the second reduction potential) was found to be sensitive to the steric and electronic effects of hydrogen donors as well as the number of hydroxyl groups present thus, could differentiate the binding abilities of alcohols and diols. As for phenylenediamines, their oxidized forms are such strong hydrogen donors that pyridine and its derivatives and even the alcohols and diols could be categorized as bases or hydrogen acceptors. Yet, their voltammetric response could also measure the hydrogen donor strengths of trifluoroethanol and acetic acid because the neutral species predominantly behaves as a hydrogen acceptor. Finally, the voltammetric behavior of quinones and phenylenediamines were explored for the purpose of measuring the moisture content of carbonyl and protic organic solvents as well as applied to detect impurities in nitrile solvents that were commonly used for electrochemistry.