2-((2-Cyanoethyl)(4-((2-cyano-4-nitrophenyl)azo)phenyl)amino)ethylisobutyrate 73309-52-1 EINECS 277-379-6 Propanoic acid, 2-methyl-, 2-((2-cyanoethyl)(4-((2-cyano-4-nitrophenyl)azo)phenyl)amino)ethyl ester