Optical and Raman Experiments for the Electro-organic Synthesis of Bromothymol Blue and Bromophenol Blue

Recently, a Journal of Chemistry Didactics claimed that bromothymol blue and bromophenol blue could be prepared in situ by oxidation of bromide to bromine, which subsequently reacts with thymol blue and phenol red, respectively. The hypothesis has now been unequivocally confirmed by absorbtovoltammetry and Raman voltammetry. The substitution of bromine by bromide is an important contribution to experiments with less hazardous materials in chemistry education. In Germany, students are not allowed to experiment with bromine. On the other hand, there are many experiments that use bromine. Therefore, the in situ electrochemical generation of bromine from bromide can be a good alternative in terms of green chemistry.