Case: Read the passage and answer the questions

There are several methods to prepare halo alkanes and haloarenes. One of the methods is to prepare from alcohol. The hydroxyl group of an alcohol is replaced by halogen on reaction with concentrated halogen acids, phosphorus halides or thionyl chloride. The halo alkanes are prepared by treating alkane with a limited amount of halogen in presence of halogen carrier and sunlight or heat. Adding hydrogen halide to alkene also results in the formation of halo alkanes. Haloarenes are prepared from hydrocarbons by electrophilic substitution and amines by Sandmeyer’s reaction.

What is the reagent used in halogenation of alkene?

CCl₄

In the laboratory, addition of bromine in CCl₄ to an alkene resulting in discharge of reddish brown colour of bromine constitutes an important method for the detection of double bond in a molecule.