Patent GB-824489-A (GB)
Title: Process for the manufacture of aromatic diazonium compounds
Filed: 1956-04-23
Abstract: Aromatic diazonium compounds are prepared by treating an aromatic compound other than a primary amine, with a nitrosyl derivative of an inorganic acid in the presence of sulphuric acid and/or a substantially non-aqueous inert organic liquid medium. The nitrosyl derivative may be the chloride, bromide, hydrogen sulphate or perchlorate and may be prepared externally or preferably in situ, e.g. by dissolving sodium nitrite in excess sulphuric acid and then adding the aromatic compound.  The organic medium may be nitrobenzene and the reaction takes place at a normal or slightly elevated temperature, often in an inert atmosphere such as nitrogen, hydrogen or carbon dioxide.  The aromatic reactant may be a substituted benzene, naphthalene or polycyclic compound; when more reactive compounds are used, e.g. bearing alkyl or alkoxy substituents, the reaction is carried out in sulphuric acid-nitrobenzene, but when less reactive compounds are used, e.g. bearing sulphonic acid, chlorine or nitro substituents, the reaction is preferably carried out in sulphuric acid in the presence of 0.001 to 0.05 mols. of a mercury compound, e.g. the oxide.  In the examples using nitrosyl hydrogen sulphate mesitylene gives 2,4,6-trimethyl benzene diazonium sulphate, toluene gives methyl benzene diazonium sulphate, sodium naphthalene-1-sulphonate in the presence of mercury oxide gives 1-sulpho-naphthalene diazonium sulphate, toluene - 4 - sulphonic acid in the presence of mercury oxide gives 2-methyl-5-sulpho-benzene diazonium sulphate, p-toluic acid in the presence of mercury oxide gives 2-methyl-5-carboxy-benzene diazonium sulphate, p-nitroanisole in the presence of mercury oxide gives 2-methoxy-5-nitro-benzene diazonium sulphate, anisole in the presence of nitrobenzene and nitrosyl sulphuric acid prepared from fuming nitric acid and sulphur trioxide, gives methoxy benzene diazonium sulphate, xylene gives dimethyl benzene diazonium sulphate; using nitrosyl chloride and ethanol as solvent phenol gives 4-hydroxy benzene diazonium chloride and dimethylaniline gives 4-dimethylamino benzene diazonium chloride.ALSO:Aromatic diazonium compounds, which may be coupled to give azo dyes, are prepared by treating an aromatic compound other than a primary amine, with a nitrosyl derivative of an inorganic acid in the presence of sulphuric acid and/or a substantially non-aqueous inert organic liquid medium.  The nitrosyl derivative may be the chloride, bromide, hydrogen sulphate or perchlorate and may be prepared externally or preferably in situ e.g. by dissolving sodium nitrite in excess sulphuric acid and then adding the aromatic compound.  The organic medium may be nitrobenzene and the reaction takes place at a normal or slightly elevated temperature, often in an inert atmosphere such as nitrogen, hydrogen or carbon dioxide.  The aromatic reactant may be a substituted benzene, naphthalene or polycyclic compound; when more reactive compounds are used, e.g. bearing alkyl or alkoxy substituents the reaction is carried out in sulphuric acid-nitrobenzene but when less reactive compounds are used, e.g. bearing sulphonic acid, chlorine or nitro substituents the reaction is preferably carried out in sulphuric acid in the presence of 0.001 to 0.05 mol. of a mercury compound, e.g. the oxide.  In the examples using nitrosyl hydrogen sulphate mesitylene gives 2,4,6-trimethyl benzene diazonium sulphate which is coupled with alkaline 2-naphthol, toluene gives methyl benzene diazonium sulphate, sodium naphthalene-1-sulphonate in the presence of mercury oxide gives 1-sulpho-naphthalene diazonium sulphate which couples with 2-naphthol, toluene-4-sulphonic acid in the presence of mercury oxide gives 2-methyl-5-sulpho-benzene diazonium sulphate, p-toluic acid in the presence of mercury oxide gives 2-methyl-5-carboxy-benzene diazonium sulphate, p-nitroanisole in the presence of mercury oxide gives 2-methoxy-5-nitro-benzene diazonium sulphate, anisole in the presence of nitrobenzene and nitrosyl sulphuric acid prepared from fuming nitric acid and sulphur trioxide, gives methoxy benzene diazonium sulphate which is coupled with alkaline 2-naphthol, xylene gives dimethyl benzene diazonium sulphate; using nitrosyl chloride and ethanol as solvent phenol gives 4-hydroxy benzene diazonium chloride which is coupled with 2-naphthol, and dimethylaniline gives 4-dimethylamino benzene diazonium chloride which is coupled with 1-naphthol.