<P> Free radical halogenation typically produces a mixture of compounds mono - or multihalogenated at various positions . It is possible to predict the results of a halogenation reaction based on bond dissociation energies and the relative stabilities of the radical intermediates . Another factor to consider is the probability of reaction at each carbon atom, from a statistical point of view . </P> <P> Due to the different dipole moments of the product mixture, it may be possible to separate them by distillation . </P> <P> In hydrohalogenation, an alkene reacts with a dry hydrogen halide (HX) like hydrogen chloride (HCl) or hydrogen bromide (HBr) 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 in this reaction, the halogen is more likely to become attached to the more substituted carbon . This is an electrophilic addition reaction . Water must be absent otherwise there will be a side product of a halohydrin . The reaction is necessarily to be carried out in a dry inert solvent such as CCl or directly in the gaseous phase . The reaction of alkynes are similar, with the product being a geminal dihalide; once again, Markovnikov's rule is followed . </P> <P> Alkenes also react with halogens (X) 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 X is colored and the product is usually colorless and odorless . </P>

What are alkyl halides how are they classified