The halogens, through themselves simple inorganic molecules, react with a wide range of organic compounds, and in doing so provide new compounds in great variety and of immense practical and theoretical importance. The modes of these reactions are complex, often involving fleeting, unstable intermediates. In this 1976 book, Professor de la Mare shows how those halogenations involving the whole gamut of unsaturated organic molecules can be linked through considering them as reactions involving the development of carbocationic centres which develop through electrophilic attack by halogen and then determine the fate of the resulting intermediate. Introductory chapters describe the properties of the various halogens and their simple derivatives, and put the reactions into the context of mechanistic physical-organic chemistry in general, and of electrophilic additions and substitutions in particular. Subsequent chapters describe the reactions of the individual halogens, whilst applications to useful synthetic processes are noted.