Which of the following, upon treatment with tert- BuONa followed by addition of bromine water, fails to decolourize the colour of bromine?

Step-by-step solution

In the options, they have acidic β − H so an elimination reaction takes place and alkene will be formed. And the formed alkene decolourizes the bromine water E ⊕ addition reaction of an alkene by HOBr while in 4 it does not have β − H so, there is no formation of alkene, hence does not decolourize Br 2 water.