many of these compounds have already an established trivial name, which is endorsed by the IUPAC nomenclature, for example chloroform (trichloromethane) and methylene chloride (dichloromethane). But nowadays, IUPAC nomenclature is used. For unambiguity, this article follows the systematic naming scheme throughout. Production Haloalkanes can be produced from virtually all organic precursors. From the perspective of industry, the most important ones are alkanes and alkenes. From alkanes Alkanes react with halogens by free radical halogenation. In this reaction a hydrogen atom is removed from the alkane, then replaced by a halogen atom by reaction with a diatomic halogen molecule. Free radical halogenation typically produces a mixture of compounds mono- or multihalogenated at various positions. From alkenes and alkynes In hydrohalogenation, an alkene reacts with a dry hydrogen halide (HX) like hydrogen chloride () or hydrogen bromide () to form a mono-haloalkane. The double bond of the alkene is replaced by two new bonds, one with the halogen and one with the hydrogen atom of the hydrohalic acid. Markovnikov's rule states that hydrogen is attached to that carbon which have more number of hydrogen. Alkenes also react with halogens (X2) to form haloalkanes with two neighboring halogen atoms in a halogen addition reaction. Alkynes react similarly, forming the tetrahalo compounds. This is sometimes known as "decolorizing" the halogen, since the reagent X2 is colored and the product is usually colorless and odorless. From alcohols Alcohol can be converted to haloalkanes. Tertiary alcohol reacts with hydrochloric acid to produce tertiary choloroalkane. Primary and secondary alcohol require an activator such as zinc chloride. This reaction is exploited in the Lucas test. In the "Darzens halogenation", thionyl chloride () convert these less reactive alcohols to chlorides. Both phosphorus pentachloride () and phosphorus trichloride () function similarly. Alcohols may likewise be converted to bromoalkanes using hydrobromic acid or phosphorus tribromide (PBr3). A catalytic amount of may be used for the transformation using phosphorus and bromine; is formed in situ. Iodoalkanes may similarly be prepared using red phosphorus and iodine (equivalent to phosphorus triiodide). The Appel reaction is also useful for preparing alkyl halides. The reagent is tetrahalomethane and triphenylphosphine; the co-products are haloform and triphenylphosphine oxide. From carboxylic acids Two methods for the synthesis of haloalkanes from carboxylic acids are the Hunsdiecker reaction and the Kochi reaction. Biosynthesis Many chloro and bromoalkanes are formed naturally. The principal pathways involve the enzymes chloroperoxidase and bromoperoxidase. From amines