Conversion of o-halogenoazo compound to o-cyanoazo compound by reaction with a zinc cyanide
AssigneeBayer Aktiengesellschaft
InventorRainer Hamprecht
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Abstract
The invention relates to the preparation of o-cyanoazo dyestuffs by reaction of corresponding o-halogenoazo dyestuffs with zinc compounds of the formula Me.sub.m Zn(CN).sub.2+m wherein Me represents an alkali metal and m represents the numbers 0, 1 or 2 In the presence of small amounts of copper-I compounds. The improvement of this process as compared with the well-known CuCN-method consists in that practically metalfree dyestuffs are obtained and--moreover--that it is cheaper than the conventional process.
Claims9
In a process for the preparation of a substantially metal-free o-cyanoazo dyestuff by reaction of the corresponding o-halogenoazo dyestuff with a metal cyanide, the improvement which comprises employing as the metal cyanide a zinc compound of the formula
- Me.sub.m Zn (CN).sub.2+m
- wherein
- Me is an alkali metal and
- m is the number 0, 1, or 2,
- in the presence of 0.1-20 mol percent of a copper-I compound based on the exchangeable halogen in said o-halogenoazo dyestuff at a reaction temperature of 20.degree.-150.degree. C, and recovering the desired o-cyanoazo dyestuff containing less than 0.1% copper and zinc.
Dependencies are inferred from the claim text.