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Method for the preparation of meta dihydroxybenzenes

  • US 4,009,212 A
  • Filed: 08/07/1975
  • Issued: 02/22/1977
  • Est. Priority Date: 02/21/1973
  • Status: Expired due to Term
First Claim
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1. A process for the preparation of dihydroxybenzenes wherein the hydroxyl radicals are in meta position to each other, the said process comprising:

  • A. heating in the presence of sulfuric acid and at a temperature between 25° and

    120°

    C. a hydroxybenzene having the formula ##STR3## in which R and R'"'"' are each selected from the group consisting of hydrogen and an alkyl radical having inclusively from one to four carbon atoms in the alkyl chain, the total number of carbon atoms in radicals R and R'"'"' being at most four, thereby forming a mixture of sulfonic acid isomers;

    B. isomerizing the said mixture in the presence of sulfuric acid at a temperature of between 130° and

    200°

    C to obtain an isomeric mixture containing the isomer wherein the sulfonic acid group is meta with respect to the hydroxyl group;

    C. selectively hydrolyzing in an aqueous medium at a temperature between about 100° and

    150°

    C. in the said mixture those sulfonic acid isomers in which the sulfonic acid group is in a position other than meta with respect to the hydroxyl group to produce thereby the selected hydroxybenzene of step A;

    D. caustically fusing the unhydrolyzed meta sulfonic acid remaining in the aqueous medium; and

    E. acidifying the resultant salt of the meta dihydroxybenzene to liberate the desired meta dihydroxybenzene.

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