aryl halides

Direct chlorination or bromination of benzene or other aromatic hydrocarbon gives chloroarenes and bromoarenes. These reactions are carried out in the presence of Lewis acids such as ferric or aluminium halides (FeCl 3 , FeBr 3 , AlCl 3 ) in the dark, at ordinary temperatures (310..

Haloarenes are colorless liquids or crystalline solids. Aryl halides are heavier than water. Being heavier than water, they are insoluble in water but soluble in organic solvents. The melting and boiling points of aryl halides are nearly the same a..

. The above reactions involve nucleophilic substitution process. Hence this method is not suitable for preparing aryl cyanides because aryl halides are less reactive towards nucleophilic substitution reactio..

The solution of freshly prepared aromatic diazonium salt on reaction with cuprous chloride on cuprous bromide gives corresponding aryl chloride or aryl bromide. This reaction is called sand maeyer reaction. The arylchlorides or bromides can also be prepared by Gattermann re..

. The reaction is a typical example of nucleophilic substitution reaction. Here the ammonia molecules in the first step and the amine molecules in the subsequent steps act as nucleophile..

(c) is chlorobenzene, an aryl halide because the chlorine is directly attached to the benzene ring. (a), is benzyl chloride which is a substituted haloarene, while (b) is chlorocyclohexane which is a haloalkan..

The sp 2 hybridized carbon atom in the C-X bond in haloarene molecule is more electronegative than the sp 3 hybrid carbon atom in alkyl halide. This carbon has less tendency to release electrons to the chlorine atom and so the C-Cl bond in aryl halides is less polar..

There is delocalisation of electrons in haloarenes due to resonance. For example, chlorobenzene is considered to be a resonance hybrid of the following structures:..

The halogen atom is replaced by amino group when aryl halides are heated with aqueous ammonia in the presence of cuprous oxide (catalyst) at 475 K and under a pressure of 60 atm.,..

In this test, the halide is warmed with aqueous or alcoholic KOH. The solution is then acidified with dilute HNO 3 and AgNO 3 solution is added. If precipitation occurs, it indicates alkyl, benzyl or allyl halides. If precipitation does not occur, it indicates aryl ..