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US 4,101,542 AGranted
Process for the selective destruction, by reduction, of p-coupled products of the 1-naphthol series
AssigneeBayer Aktiengesellschaft
InventorErich Kramer
Life of this patent
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Abstract
Para-coupled products of the 1-naphthol series can be destroyed in the presence of the ortho-coupled product by reduction with salts of dithionous acid or of hydroxymethanesulphinic acid or with hydrazine optionally in the presence of redox-catalysts.
Claims4
Process for the selective destruction of p-coupled product of a 1-naphthol coupler and a diazo compound in the presence of o-coupled products thereof which comprises treating said coupled products with hydrazine, hydrazine and a redox catalyst, a salt of dithionous acid or a salt of hydroxymethanesulphinic acid at a pH >
- 4 and a temperature of 10.degree.-100.degree. C to reduce said p-coupled product, and then separating the o-coupled products.
Dependencies are inferred from the claim text.