Bromine water

Bromine water is a saturated aqueous solution of bromine in water.

Properties

Since bromine is only sparingly soluble in water, produces a brown colored, dilute bromine solution. By disproportionation to bromide and hypobromite bromine water is slightly acidic:

The reaction is accelerated by light. Bromine is therefore stored in brown, slightly translucent bottles.

Use

Bromine is used in the laboratory for the rapid detection of C = C multiple bonds in organic compounds such as alkenes or alkynes. If an organic compound (eg, ethene ) is introduced as a gas into a liquid bromine or shaken with bromine water, the solution becomes colorless, the sample substance containing at least one C = C double bond. This detection is based on an electrophilic addition. The polarization and by heterolytic cleavage of positively and negatively charged bromide ions go it bonds with the p- electrons that were previously involved in the double bond.

The reaction of bromine with an alkane proceeds only with a catalyst and / or under high-energy light. There the bromine water is decolorized likewise, but it also creates more HBr, because the reaction mechanism is now a free-radical substitution. Thus, the distinction of alkanes and alkenes is very simple.

Safety

The escaping bromine vapors are highly toxic. They must not be inhaled because the bromine vapor etch the alveoli and airways. For details see Article bromine.

• Chemical Solution