Cupro-cupri sulfite

Aromatic diazonium salts on treatment with sodium nitrite decompose to form nitro compounds. This method represents a good procedure for obtaining o- and p-dinitrobenzenes, in 70% and 76% yield, respectively, from the corresponding diazonium sulfates. Improved yields in the preparation of dinitronaphthalenes are obtained when the decomposition of the diazonium sulfates is catalyzed by a cupro-cupri sulfite prepared by the interaction of copper sulfate and sodium nitrite. The procedure is illustrated by the synthesis of 1,4-dinitronaphthalene (60%). Occasionally, diazonium fluoborates are first formed, and these compounds are treated with sodium nitrite in the presence of copper powder, viz.,... 

The cupro-cupri sulfite of this variety is more efiicient as a decomposition reagent than the red-violet precipitate obtained by treating a hot solution of copper sulfate with a solution of ammonium sififite saturated with sulfur dioxide and subsequently heating the mixture for 10 minutes at 90°. 

Steam distillation of 1,4-dinitronaphthalene is very slow. However, the cupro-cupri sulfite method is a general one for the replacement of the diazonium group by the nitro group, and steam distillation is preferable whenever the product is readily volatile. 

COUMARILIC ACID, 24, 33 Coumarin, 24, 33 Coumarin dibromide, 24, 33 Coumarin, 4-methyl-, 24, 69 Coupling, of allyl chloride, 27, 7 of aryl residues, 20, 45 Crab shells, 26, 36 Creatinine, 22, 90 /i-Cresol, 2-bromo-, 23,11 Crotonaldehyde, 24, 92 27, 66 Crotonic acid, SO, 101 24, 98 26, 55 Crotonio acid, /3-anilino-, ethyl ESTER, 29, 42 Cupric acetate, 28, 45 Cupric carbonate, basic, 24, 64 Cupro-cupri sulfite, 28, 53 Cuprous bromide, 24, 22, 23 Cuprous chloride, 28, 46 Cuprous cyanide, 21, 89 24, 14, 97 28, 34... 

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