Electrophilic bromination of alkenes: environmental, health and safety aspects of new alternative methods.

More than twenty new alternative methods for bromination of alkenes have been evaluated taking into consideration their resource demands, waste production as well as environmental, health and safety aspects. The cost of bromine and the substances designated to circumvent the application of molecular bromine have also been taken into account. As bromine is only one of several problematic substances being used, its avoidance-by applying bromine supported on solid material or by performing the in situ generation of bromine-does not significantly reduce the technological requirements. On the contrary, the resource demands and amount of waste produced by most new methods are significantly higher compared to the standard methods, especially if the recycling of a carrying agent is not efficient. The method using hydrobromic acid and hydrogen peroxide can be regarded as a competitive alternative to the standard method. The application of certain carrying agents could be interesting, because solvents such as carbon tetrachloride or chloroform used during synthesis could be replaced with less problematic ones during work-up. However, problems associated with these alternatives are not resolved as yet.