How do you name compounds with halogen substituents?

Compounds with halogen substituents are named using the IUPAC system, with the halogen as a prefix to the main compound.

In the International Union of Pure and Applied Chemistry (IUPAC) system, the halogen is treated as a substituent on the main compound and is indicated by a prefix. The prefixes are fluoro- for fluorine, chloro- for chlorine, bromo- for bromine, and iodo- for iodine. The halogen is given the lowest possible number in the compound's name.

For example, consider a molecule of methane (CH4) where one of the hydrogen atoms has been replaced by a chlorine atom. This compound is named chloromethane, and its formula is CH3Cl. If two hydrogen atoms are replaced by chlorine atoms, the compound is named dichloromethane (CH2Cl2).

When naming a compound with multiple different halogens, list the halogens in alphabetical order. For instance, a compound with both bromine and chlorine would be named bromochloromethane, not chlorobromomethane.

If the compound contains a functional group, such as an alcohol or carboxylic acid, the functional group is usually considered the main part of the compound, and the halogen is treated as a substituent. For example, in 2-chloroethanol (CH2ClCH2OH), the -OH group is the functional group, and the chlorine atom is a substituent on the second carbon atom.

Remember, the goal is to provide a systematic and unambiguous name that clearly indicates the structure of the compound. Practice and familiarity with the IUPAC rules will make this process easier.