Method for synthesizing acid blue 104
AssigneePolaroid Corporation
InventorYunn H. Chiang
Life of this patent
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Abstract
There is described a method for the synthesis of Acid Blue Dye 104 (Color Index. No. 42735) wherein N-benzyl-N-ethyl-toluidinesulfonic acid is reacted with p-diethylaminobenzaldehyde to form leuco Acid Blue Dye 104 which is then isolated and purified with a solvent such as a lower alcohol to provide a very high purity product. The leuco dye is dissolved in a buffer solution of acetic acid and oxalic acid and oxidized by rapidly adding sodium dichromate solution. The Acid Blue Dye is collected and purified to obtain a final product of very high purity and optical transparency.
Claims5
A method for synthesizing Acid Blue Dye 104 which is represented by the formula ##STR2## which comprises the steps of:
- (a) reacting N-benzyl-N-ethyl-toluidinesulfonic acid with p-diethylaminobenzaldehyde in an aqueous oxalic acid solution having a pH of about 1.5 or less to form an intermediate which is represented by the formula ##STR3## (b) isolating said intermediate and removing impurities therefrom by treatment with an organic solvent;
- (c) providing a homogeneous aqueous buffer solution having at least about 3.5 weight percent of oxalic acid and at least about 35 weight percent of acetic acid based on the volume of said solution;
- (d) dissolving said intermediate in said homogeneous buffer solution at a ratio of at least about 20 liters of buffer solution per mole of said intermediate;
- (e) adding aqueous sodium dichromate solution to said solution of said intermediate at a temperature of from about -5.degree. C. to about -10.degree. C. and intimately mixing said solutions in about 60 seconds or less to form said Acid Blue Dye 104;
- (f) isolating said Acid Blue Dye 104;
- and
- (g) purifying said Acid Blue Dye 104 by dissolution in sulfuric acid and partially neutralizing the solution with a base.
Dependencies are inferred from the claim text.