Patents by Inventor Charles H. Chang

Charles H. Chang has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Process for preparing 5-halo-2,3-phenylenediamine-1-carboxylic acid
    Patent number: 3931303
    Abstract: Method of preparing 5-halo-2,3-phenylenediamine-1-carboxylic acids having the following formula: ##SPC1##Wherein X is Cl, Br or F by reacting a 2,5-dihalo-3-nitrobenzoic acid with ammonium hydroxide to yield 5-halo-3-nitro anthranilic acid followed by a reduction of the resultant product. The 5-halo-2,3-phenylenediamine-1-carboxylic acids are useful as herbicides and as intermediates for use in the preparation of dyestuffs, photographic developers, pharmaceuticals, antioxidants and the like.
    Type: Grant
    Filed: June 28, 1973
    Date of Patent: January 6, 1976
    Assignee: GAF Corporation
    Inventors: Charles H. Chang, David I. Randall