One of the methods the body uses for detoxifying certain chemicals is a process called conjugation. The toxin is combined with another chemical such as glutathione in the liver to produce a less toxic and easily excreted compound. In order to do this the body needs a "handle" on the toxin molecule, a site where conjugation can take place. This can be as simple as a carboxyi (-COOH) group. A classic example where conjugation cannot take place since there is no handle, is carbon tetrachloride CCl4. To a lesser extent the simple hydrocarbons such as trichloroethane CH3CCl3 all have this problem.