Alkylhalidit

Alkylhalidit, commonly called alkyl halides or haloalkanes, are organic compounds in which an alkyl group R is bonded to a halogen X (fluorine, chlorine, bromine or iodine). The general formula is R–X, and the halogen replaces a hydrogen on the alkyl chain. They are classified as primary, secondary or tertiary according to the degree of substitution at the carbon bearing the halogen.

Nomenclature and classification are typically follows substitutive naming: haloalkanes are named as alkyl halides when the halogen is the suffix’s substituent and as haloalkanes in common usage. The identity of the halogen (fluoro-, chloro-, bromo-, iodo-) strongly influences reactivity and properties.

Properties of alkyl halides include a polar C–X bond, which imparts higher polarity than nonhalogenated hydrocarbons. Boiling points generally rise with increasing molecular weight and with heavier halogens. They are usually immiscible with water and are more soluble in organic solvents. The leaving-group ability of the halogen follows I > Br > Cl > F, influencing reaction pathways such as substitution and elimination.

Reactions of alkyl halides are dominated by nucleophilic substitution (SN1 and SN2) and elimination (E1 and E2). SN2 rates are higher for less substituted substrates; SN1 dominates for more substituted, often with polar solvents. Elimination competes with substitution under basic conditions, yielding alkenes. Alkyl halides can also act as precursors to other reagents via exchange or coupling reactions.

Synthesis routes include conversion of alcohols to alkyl halides using reagents like HX or converting alcohols with thionyl or phosphorus halides, and hydrohalogenation of alkenes. Some alkyl halides are used as solvents, intermediates in chemical synthesis, or in the production of agrichemicals and pharmaceuticals. Safety concerns include toxicity, irritation and environmental persistence; responsible handling and regulation are important in industrial contexts.