Even though the halides
are reactive, the hydrocarbon portions of the molecules still retain
their identity. When the Cl
of ethyl chloride (CHCHCl)
is replaced by an OH,
the molecule becomes ethyl alcohol (CHCHOH),
which has properties similar to other alcohols. With COOH
the molecule becomes an organic acid, and with NH,
a base. Because groups such as Cl,
determine the gross chemical properties of the molecule, they are
known as functional groups.
The hydrocarbon chains attached to the functional groups modify
the properties of the functional groups while maintaining their
essential chemical character. Methyl alcohol, CHOH,
is water-soluble, whereas dodecyl alcohol,
is not; but they both show the chemical properties of an alcohol.