The structure of the product that is formed from the addition reaction between but-2-ene and chlorine, Cl₂, is A - VCE - SSCE Chemistry - Question 2 - 2011 - Paper 1

Chlorine adds across the double bond of but-2-ene, resulting in the formation of 2,3-dichlorobutane. In addition reactions, each carbon of the double bond becomes bonded to a chlorine atom. Thus, the correct structure is represented by option C:

    Cl       H
    H - C - C - H
          H       H
          H - C - C - H
            Cl

This indicates that each of the formerly double-bonded carbons is now connected to a chlorine atom.