was it the bromine water that decolourised cyclohexene or the cyclohexene that decolourised the bromine water?
The cyclohexane contains only single bonded carbon atoms and does not react with the bromine water because the alkane is saturated. Therefore no reaction takes place, hence the solution remains red in colour. However, the cyclohexene contains a reactve double bond which is high in electron density. Therefore it reacts with the bromine water and causes the decolourising of the solution.
