Iso-Nitroso compounds

The remainder of the distillation must be conducted with extreme care. As soon as the ethyl oxomalonate has partly distilled over and the temperature has risen somewhat, the remaining iso-nitroso compound begins to decompose and sometimes liberates gases so rapidly that the thermometer and capillary tube may be blown out of the flask. If the manometer is watched closely, and at the first sign of liberation of gas, as evinced by a sudden increase in pressure, a wet towel is placed around the flask, the reaction can be slowed down. 

Reaction LXXXVm. Action of Nitrous Acid on the Monoximes of a-Diketones. (A., 274, 71.)—When compounds containing the group —CH2—CO—are treated with nitrous acid in presence of sodium, an iso-nitroso compound identical with the monoxime of the corresponding oc-diketone is obtained (see p. 111). From the monoxime by the further action of nitrous acid in the presence of glacial acetic acid, the diketone itself is formed. 

This imino derivative with nitrous acid gives an iso-nitroso compound that by reduction with ammonium sulphide yields a di-amino compound as follows ... 

They are very generally regarded as iso-nitroso compounds. 

Iso-nitroso and Oxime Compounds.—This iso-nitroso derivative of the mono-ketone (methyl ethyl ketone) is also an oxime of the di-ketone (di-acetyl) as may be shown by the following relationships. 

This rearrangement of nitroso derivatives into iso-nitroso derivatives or oximes is of especial importance in connection with the benzene compounds and a group of nitroso dyes. The oxime yields the diketone when hydrolyzed by boiling with dilute sulphuric acid, as above. Di-acetyl, being a di-ketone, reacts in all respects as a di-carbonyl compound especially in yielding both the mono-oxime as above and also a di-oxime. 

These nitroso nitro compounds were converted to amines and diamines, probably as mixtures of isomers. For example, the 2,3-dihydro-l /f-indene-1,2-diamine hydrochloride prepared via 2,3-dihydro-2-nitro-l/f-inden-l-one oxime has mp 280 °C (dec)92, while the authentic cis-iso-mer93 has mp 304-308 °C. Furthermore, 2,3-dihydro-l-methyl-l//-inden-2-amine obtained by direct hydrogenation of the l-methyl-17/-indene derivative92 has the same melting point (201 — 202 "C) as the 1 1 mixture of the cis- and trans-isomers94. 

Phenyl Nitroso Amine.—The iso-diazotate differs in a noticeable way from the diazotate. Not only is it more stable, but on treatment with acids it does not yield diazonium salts, but an entirely different compound, viz., phenyl nitroso amine, CeHs—NH—NO. This compound has the same composition as the diazo hydroxide and the relationship means that the isomeric diazo hydroxide undergoes structural rearrangement into a new compound. This is the reason for the view that this same compound, phenyl nitroso amine, is an intermediate product in the formation of diazo. compounds as already referred to (p. 587). These relationships may be shown as follows ... 

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