Natural bromine is a mixture of two stable isotopes: bromine-79 (50.54 percent) and bromine-81 (49.46 percent).
Theobromine gets its name not from the element bromine, but from the genus of the cacao tree Theobroma cacao ("food of the gods" in Greek).
For they think they have worked out a way to make both the liquids and the electrodes cheap.The solution Dr Huskinson and Dr Marshak propose, in a paper in Nature, is to use molecules called quinones, mixed with sulphuric acid, on one side of the membrane, and a mixture of bromine and hydrobromic acid on the other and to make the electrodes out of carbon.
At present the researchers need to use bromine, a particularly toxic material, on one of the electrodes to boost performance.
The anthraquinone they chose, called AQDS, reacts with the sulphuric acid in a way complementary, with a suitable transfer of hydrogen ions, to the way bromine turns into bromide ions, the non-hydrogen part of hydrobromic acid.
Several firms are trying zinc and bromine in electrolytes and others iron and chromium.
The solution is known as bromine water.
A typical bimolecular substitution reaction is shown by the equation in which the chemical symbols represent atoms of the elements as above (with Br the symbol for an atom of bromine and N the symbol for any nucleophilic agent).
Similarly, the substitution of anion X− by Y− in an A+X− compound represents a simple anionic substitution; this is exemplified by the replacement of Cl− (chlorine ions) with Br− (bromine ions) in the structure of KCl (potassium chloride).
Treatment of a compound that contains an aromatic ring with chlorine or bromine in the presence of a catalyst, typically iron (Fe) or an iron III) halide (FeX3), brings about electrophilic aromatic substitution of one of the ring hydrogen atoms by the halogen.
