Preparation of monohalohydroquinone monocarboxylates/dicarboxylates
AssigneeRhone-Poulenc Specialites Chimiques
InventorSerge Ratton
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Abstract
Monohalohydroquinone monocarboxylates are selectively prepared by halogenating a hydroquinone monocarboxylate, or admixture thereof with a hydroquinine dicarboxylate and a minor amount of hydroquinone, with a chlorine, bromine or sulfuryl halide halogenating agent; such monocarboxylates are facilely converted into the corresponding dicarboxylates by acylation. Both the monocarboxylates, e.g., monochlorohydroquinone monoacetate, and dicarboxylates, e.g., monochlorohydroquinone diacetate, are useful organic intermediates.
Claims34
A process for the preparation of a monohalohydroquinone monocarboxylate, comprising halogenating a hydroquinone monocarboxylate having the formula:
- ##STR4## wherein R is a straight of branched chain alkyl radical containing from 1 to 4 carbon atoms, or an admixture of said hydroquinone monocarboxylate with a hydroquinone dicarboxylate and a minor amount of hydroquinone, said minor amount of hydroquinone being less than the amount of hydroquinone monocarboxylate and hydroquinone dicarboxylate with chlorine, bromine or sulfuryl halide halogenating agent, in a substantially anhydrous carboxylic acid reaction medium comprising an alkanoic acid having from 1 to 8 carbon atoms.
The process as defined by claim 20, comprising carrying out said acylation in the presence of a catalytically effective amount of a strong acid having a pK of less than 1 in water at 25.degree. C. in a carboxylic acid reaction medium which is liquid under the conditions of acylation.
A process for the preparation of a monohalohydroquinone monocarboxylate, comprising (i) first reacting a hydroquinone dicarboxylate with hydroquinone wherein the molar ratio of hydroquinone dicarboxylate to hydroquinone is at least 1.5, and thence (ii) halogenating the reaction admixture which results, comprising a hydroquinone monocarboxylate having the formula:
- ##STR5## wherein R is a straight or branched chain alkyl radical containing from 1 to 4 carbon atoms, a hydroquinone dicarboxylate and a minor amount of hydroquinone, with chlorine, bromine or sulfuryl halide halogenating agent, in a substantially anhydrous carboxylic acid reaction medium comprising an alkanoic acid having from 1 to 8 carbon atoms.
Dependencies are inferred from the claim text.