ON OUR PRESENT KNOWLEDGE OF AROMATIC DIAZO-COMPOUNDS. 193 



Alkyl Diaao-oxides. — The action of methyl iodide on the metallic iso- 

 diazo-oxides indicates that the isodiazo-hydroxide itself is a tautomeric 

 substance, for the potassium salt yields a nitrosamine R.NCH3NO, whilst 

 the silver derivative gives rise to an 0-ether, R.N : NOMe, this substance 

 being also produced from the silver derivative of the normal diazo- 

 hydroxide. This result indicates that the isomeric diazo- hydroxides 

 corresponding with the two silver derivatives both have the same struc- 

 tural formula, Il.N:NOH. These 0-ethers contain the diazo-i-adicle 

 N : N, for they are all explosive and readily couple with the phenols in 

 alkaline solutions. "^ 



Reduction of the MetalliG Diazo-oxides. — The members of both series, 

 ■when treated Avith sodium amalgam, yield the corresponding hydrazines, 

 provided that the i-eaction takes place in excess of alkali hydroxide.^ 



Oxidation of the Metallic Diazo-oxides ; the Aromatic Diazoic Acids.— 

 Even before the discovery of the i^'odiazo-oompounds Bamberger had 

 prepared acidic substances by the oxidation of the diazonium salts in 

 alkaline solutions, and on repeating the experiment with the alkali iso- 

 diazo-oxides he obtained a larger yield of the oxidation product.-^ These 

 acidic substances, the aromatic diazoic acids, are also obtained eitlier by 

 dehydrating the nitrates of the primary aromatic amines, 



R .NH2HNO3 - HoO = R.NH.NO2, 



or by the direct action of nitric anhydride on these bases, 



2RNH2+N,,05 = H^O + ^RNH.KOo. 



They readily undergo molecular rearrangement, yielding nitro-amines, the 

 nitroxyl radicles entering the nucleus either in the ortho- or para-position 

 with respect to the aminic nitrogen.^ These properties indicate that the 

 diazoic acids are nitramines ; nevertheless they behave as tautomeric 

 substances, for whereas their alkali salts give rise to secondary nitramines, 

 their silver derivatives furnish 0-esters, 



r potassium salt ->■ CgHjNCHa.NO.j 

 r TT -WTT^rn J methylphenylnitramine. 



^'^^^^^^^n silver salt -^ CeHgNrNOOCHs 



(_ methyl benzenediazoate. 



The methyl 0-ester, when boiled with a benzene solution of /3-uaphtholj 

 yields benzene-azo-/3-naphthol, this condensation indicating its relationship 

 to the diazo-compounds. 



The Isomeric Diazo-oxides and the Schotten-Bo^.imann Reaction. — The 

 normal and iso-diazo-oxides, when treated with benzoyl chloride, yield 

 nitrosobenzanilide with equal readiness, provided that the reaction is 

 performed in the presence of a large excess of alkali hydroxide. The 

 arnount of benzoyl derivative produced is very small when the mixture is 

 only slightly alkaline, the diminution in yield being greatest in the case 

 of the normal isomeride.' This reaction, at first sight, seems to favour 

 the nitrosamine formula for the diazo-oxides 



CgHjNHNO -> C^H5N(NO).COCaH5, 



' Bamberger, Ber., 1895, 28, 225. ' Hantzsch, Her., 1898, 31, 3J0. 



' Ber., 1894, 27, 911. 



* Bamberger, Ber., 1803. 26, 471 ; 1891, 27, 359, 584, 2G0I. 

 » Hantzsch, Bnr.. 1897, 30, G21. 

 1902. o 



