alkylhalogenidiin

Alkylhalogenidiin, commonly known as alkyl halides or haloalkanes, are organic compounds consisting of an alkyl group (R–) bonded to a halogen atom (X = F, Cl, Br, I). They range from simple methyl and ethyl halides to more complex branched and cyclic structures. The general formula is R–X, and the halogen atom serves as a leaving group in many reactions.

The C–X bond in alkyl halides is polar, with the halogen being more electronegative than carbon. The leaving-group ability increases with halogen size, so iodides and bromides generally undergo substitution and elimination more readily than chlorides and fluorides. Alkyl halides are classified by the degree of substitution of the carbon bearing the halogen: primary, secondary, or tertiary.

Nomenclature follows the IUPAC system, often referred to as haloalkanes. Examples include chloromethane (methyl chloride, CH3Cl), bromomethane (bromomethane, CH3Br), and iodobutane (C4H9I). They can also be described by the attached alkyl group, such as ethyl chloride (CH3CH2Cl).

Synthesis of alkyl halides commonly proceeds from alcohols, using reagents such as thionyl chloride (SOCl2) for chlorides, phosphorus tribromide (PBr3) for bromides, or phosphorus trifluoride (PF3) for fluorides. They can also be produced by radical halogenation of alkanes or by converting carboxylic derivatives. Reactions of alkyl halides include nucleophilic substitution (SN1 and SN2) and elimination (E1 and E2) pathways, as well as use as alkylating agents in various organic syntheses.

Safety and environmental considerations are important: many alkyl halides are volatile and toxic, and some, notably chlorofluorocarbons and related compounds, have had significant environmental impacts.