Preparation of Azo Dyes
UNIVERSITY OF SAN CARLOS
DEPARTMENT OF CHEMISTRY
NAME: Maniwang, Ma. Aiza C. DATE: March 21, 2011
COURSE: BS Chemistry II APPROVED: ___________
PREPARATION OF AZO DYES
ABSTRACT
In this experiment, the azo dyes p-nitrobenzene azoresorcinol and methyl orange were prepared by the azo coupling reaction. The p-nitrobenzene azoresorcinol dye was prepared from p-nitroaniline and resorcinol. The diazonium salt formed was from the reaction of the cold solution of dissolved p-nitroaniline in hydrochloric acid and water with the solution of sodium nitrite. Azo coupling was then followed by letting the diazonium react with a solution of resorcinol in water and sodium hydroxide. The resulting mixture was treated with excess hydrochloric acid turning the mixture to a color red. After suction filtration and drying, a red-brown powder was obtained as a final product.
Furthermore, synthesis of methyl orange was prepared from sulfanilic acid and N,N-dimethylaniline. The sodium diazobenzenesulfonate was made by the diazotization of the sulfanilic acid and sodium hydroxide mixture with a solution of sodium nitrite which was then cooled. Coupling reaction occurred when the solution of sodium diazobenzenesulfonate was mixed with a solution of N,N-dimethylaniline in hydrochloric acid. The first product obtained from the coupling was a bright red acid form of methyl orange called helianthin. In basic medium, through the addition of a dilute solution of sodium hydroxide, helianthin is converted to the orange sodium salt known as the methyl orange.
INTRODUCTION
Para-nitrobenzeneazoresorcinol dye and methyl orange belong to a class of dyes known as “azo colors” which contain the azo group linked to two aromatic nuclei. The nature of the aromatic substituent’s on both sides of the azo group (-N=N-) controls the colors of the azo compound as well as the water- solubility of dyes and how well they bind to a particular fabric. In addition to the azo group, the dyes
DEPARTMENT OF CHEMISTRY
NAME: Maniwang, Ma. Aiza C. DATE: March 21, 2011
COURSE: BS Chemistry II APPROVED: ___________
PREPARATION OF AZO DYES
ABSTRACT
In this experiment, the azo dyes p-nitrobenzene azoresorcinol and methyl orange were prepared by the azo coupling reaction. The p-nitrobenzene azoresorcinol dye was prepared from p-nitroaniline and resorcinol. The diazonium salt formed was from the reaction of the cold solution of dissolved p-nitroaniline in hydrochloric acid and water with the solution of sodium nitrite. Azo coupling was then followed by letting the diazonium react with a solution of resorcinol in water and sodium hydroxide. The resulting mixture was treated with excess hydrochloric acid turning the mixture to a color red. After suction filtration and drying, a red-brown powder was obtained as a final product.
Furthermore, synthesis of methyl orange was prepared from sulfanilic acid and N,N-dimethylaniline. The sodium diazobenzenesulfonate was made by the diazotization of the sulfanilic acid and sodium hydroxide mixture with a solution of sodium nitrite which was then cooled. Coupling reaction occurred when the solution of sodium diazobenzenesulfonate was mixed with a solution of N,N-dimethylaniline in hydrochloric acid. The first product obtained from the coupling was a bright red acid form of methyl orange called helianthin. In basic medium, through the addition of a dilute solution of sodium hydroxide, helianthin is converted to the orange sodium salt known as the methyl orange.
INTRODUCTION
Para-nitrobenzeneazoresorcinol dye and methyl orange belong to a class of dyes known as “azo colors” which contain the azo group linked to two aromatic nuclei. The nature of the aromatic substituent’s on both sides of the azo group (-N=N-) controls the colors of the azo compound as well as the water- solubility of dyes and how well they bind to a particular fabric. In addition to the azo group, the dyes
References: Introduction to Organic Laboratory Techniques A Contemporary Approach (1976) by Donald L. Paris, Gary M. Lampman and George S. Kriz, Jr. Laboratory Experiments in Organic Chemistry 6th Edition (1970) by Roger Adams, John R. Johnson, Charles F. Wilcox Jr. phoenix.liu.edu/~nmatsuna/che122/exp17.pdf Date accessed: March 5, 2011 Principles of Modern Organic Chemistry by Cason, James