Final answer:
For the compound C2H2Cl2, the IUPAC name can vary as 1,1-dichloroethene or 1,2-dichloroethene, depending on the positions of chlorine atoms. Since double bonds are present, 'ethene' is used in the name. The correct IUPAC name for this structure is 1,2-dichloroethene.
Step-by-step explanation:
The compound C₂H₂Cl₂ can have different IUPAC names depending on the position of the chlorine atoms. If the chlorines are on the same carbon atom, the name is 1,1-dichloroethene. If the chlorines are on different carbon atoms, the name is 1,2-dichloroethene. Since there is only one structure for a compound with two carbon atoms and two chlorines (ignoring cis or trans isomers), both chlorines must be on adjacent carbon atoms. As there is a double bond in the compound, it is an ethene, not an ethane. So, according to IUPAC notation, which omits the number 1 for substituents on the first carbon, the name is 1,2-dichloroethene.