Chemistry · Ch 6 — Haloalkanes and Haloarenes
Introduction
Introduction
Haloalkanes and haloarenes are the two families of compounds formed when one or more hydrogen atoms of a hydrocarbon are replaced by a halogen atom (F, Cl, Br or I). The distinction between the two names comes from where that replacement happens: in a haloalkane, the halogen sits on an -hybridised carbon of an alkyl (aliphatic) group, while in a haloarene, the halogen is attached directly to an -hybridised carbon of an aryl (aromatic) ring.
Why This Family of Compounds Matters
Halogenated organic compounds are not just laboratory curiosities — many occur naturally and several are clinically important. A chlorine-containing antibiotic, chloramphenicol, is produced by microorganisms and is an effective treatment for typhoid fever. The human body itself makes an iodine-containing hormone, thyroxine; when its production falls short, the deficiency causes a disease called goiter. On the synthetic side, chloroquine is used to treat malaria, and halothane serves as an anaesthetic during surgery. Certain fully fluorinated compounds are even being explored as potential blood substitutes.
Beyond medicine, haloalkanes and haloarenes are widely used across industry and everyday life — chiefly as solvents for relatively non-polar substances, and as starting materials from which a wide range of other organic compounds can be synthesised.
Halogenated compounds tend to persist in the environment because soil bacteria are largely unable to break them down — a property that makes their industrial use a genuine environmental concern, not only a chemistry one.
What This Unit Covers
This unit builds up the chemistry of organohalogen compounds systematically: how haloalkanes and haloarenes are classified and named, the methods used to prepare them, their physical and chemical properties (including the reaction mechanisms that explain why they behave the way they do), and the practical uses — and hazards — that follow from those properties.