Alkyl and aryl nitro compounds behave differently. The mixed aryl and alkyl boron chlorides are also of known. Another class of common electrophiles are aryl and heterocyclic halides. Nitrites have the general formula RONO, where R is an aryl or alkyl group. It involves migration of an acyl group of phenol ester to the aryl ring. Cyclization reactions of vinyl, aryl, and acyl radicals are also known. This reaction is general for aryl sulfonic acids. For the arylation of amines with unactivated aryl halides, the Buchwald-Hartwig reaction is useful. An arylcyclohexylamine is composed of a cyclohexylamine unit with an aryl moiety attachment. The Claisen rearrangement of aryl ethers can also be performed as a photochemical reaction. Even aryl halides participate in this reaction. Some of these naturally occurring aryl halides exhibit useful medicinal properties. Flutamide has been identified as an agonist of the aryl hydrocarbon receptor. It is also possible to functionalize silicon wafers with diazonium salts forming an aryl monolayer. It is sometimes used in the synthesis of aryl amines.