Pixel International Conferences

Electrosynthetic methods can play an important role in industrial processes for a more sustainable economy based on renewable energies. In order to demonstrate these techniques and the associated benefits, the introduction of electrochemical processes beyond batteries and fuel cells into chemistry classes is very well suited to emphasize the significance of chemistry to overcome the current fossil age.

The electrosynthesis of intensely colored substances (e.g. organic dyes) like bromocresol green are particularly suitable for the implementation in a chemistry course since the distinct color allows the use of only small amounts of substance and therefore short reaction times. Furthermore, the color change can be used to monitor the reaction progress visually as well as (semi-)quantitatively using UV/Vis spectroscopy. The proposed model experiment consists of the electrosynthetic bromination of cresol purple with potassium bromide as bromine source in acetic acid using graphite electrodes at moderate voltages. Both, cresol purple and the product bromocresol green, are pH indicators but differ in their colors and transistion ranges which can be confirmed experimentally by the students.

We’ve chosen an electrosynthetic bromination reaction as a model experiment, since important green chemistry principles can be easily demonstrated by generating the bromination agent in-situ: Avoiding the addition of elemental bromine to the reaction mixture clearly establishes a less hazardeous synthesis and also obsoletes the need to store large quantities of toxic and corrosive substances on site. Additionally, spectroscopic monitoring of the reaction mixture prevents from accumulating excess bromine and ensures to detect when the reaction is complete, resulting in an efficient use of electric energy.

Keywords: Electrosynthesis, Green Chemistry, Lab Experiment