When toluene and a bromine solution react, there is no reaction. That is, the solution turns a yellow/brown colour, the same as the bromine solution.
I conducted an experiment where toluene and a bromine solution were meant to be catalysed by iron filings. However, instead of the solution losing its colour (like you'd expect in an alkene/alkyne), it became rustic in colour. If the iron filings were intended to catalyse the reaction, why did the solution become darker? The reaction that took place seems entirely counter-intuitive.