Previous studies from this laboratory have involved the characterization of adiponitrile (NCCH2CH2CH2CH2CN) / tetraethylammonium tetrafluoroborate (TEABF4) as a versatile solvent system for organic electrochemistry (1,2). One very valuable feature of this system is the wide potential limit range, as noted by others (3). Considering that the positive potential limit is +5 V vs Ag/AgCl, the system is particularly attractive for the study of hydrocarbon oxidation. The present paper is a continuation of the study of various hydrocarbons in adiponitrile (4).

Experimental

Adiponitrile was obtained from Sigma-Aldrich Corporation, and tetraethylammonium tetrafluoroborate (TEA BF₄) was purchased from Southwestern Analytical Chemicals. Cyclic voltammograms were obtained on a PAR 283 potentiostat using PowerSuite software. Potentials are referenced against a Ag/AgCl reference electrode (1). Platinum and glassy carbon electrodes (1 mm diameter each) were obtained from eDAQ.

Results and Discussion

Cyclic voltammograms of 6.8 mM toluene in adiponitrile / 0.2 M TEABF₄ are shown in the attached figure. An initial positive scan at platinum from 0.00 V produced a multicomponent, irreversible oxidation process between +2V and +3V vs Ag/AgCl, with considerable current on the second sweep (not shown). Results at glassy carbon were somewhat similar; however, there is little evidence of multiple oxidation processes. In addition, the lack of oxidation current on the second sweep at glassy carbon indicates that considerable electrode filming at glassy carbon is involved. Reported peak potentials in acetonitrile / NaClO₄ are similar to the values observed in the present study (5). This study shows that adiponitrile / 0.2 M TEA BF₄ is a useful solvent system for the electrochemical study of toluene.

References

1. G.T. Cheek, ECS Trans., 58(46), 45-51 (2014).

2. G.T. Cheek, ECS Trans., 61(30), 19-24 (2104).

3. H. Duncan, N. Salem, and Y. Abu-Lebdeh, J. Electrochem. Soc., 160(6) A838-A848 (2013).

4. G.T. Cheek, ECS Trans., 72(26), 1-5 (2016).

5. W.C. Neikam and M.M. Desmond, J. Am. Chem. Soc., 86, 4811-4814 (1964).

Figure 1. Cyclic voltammograms of 6.8 mM toluene in adiponitrile / 0.2 M TEA BF₄ at 100 mV/s.

Black (solid) curve : Platinum ; Red (dotted) curve : Glassy carbon