Process for the preparation of metachlorophenols
AssigneeRhone-Poulenc Specialites Chimiques
InventorGeorges Cordier
Life of this patent
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Abstract
The invention relates to a process for the preparation of metachlorophenols. The process consists in selectively hydrodechlorinating, under the action of heat and in the liquid phase, polychlorophenols containing at least one chlorine atom in the meta position relative to the phenolic hydroxyl, by reacting these polychlorophenols with hydriodic acid in a quantity which is sufficient in relation to the chlorine atoms to be removed. The metachlorophenols obtained are organic synthesis intermediates.
Claims25
A process for the preparation of a meta-chlorophenol, comprising selectively hydrodechlorinating with hydriodic acid, in liquid phase, a polychlorophenol having the general formula (I):
- ##STR3## wherein X.sub.1 and X.sub.2, which are identical or different, are each chloro, hydrogen, alkyl, aryl, arylakyl, alkoxy or aryloxy, with the proviso that at least one of X.sub.1 and X.sub.2 is chloro, and R.sub.1, R.sub.2, and R.sub.3, which are identical or different, are each chloro, hydrogen, alkyl, aryl, arylakyl, alkoxy or aryloxy, with the proviso that at least one of R.sub.1, R.sub.2 and R.sub.3 is chloro, said reaction being carried out in the presence of such amount of hydriodic acid as to hydrodechlorinate the desired number of chlorine atoms.
A process for the selective preparation of a monochlorophenol or dichlorophenol containing a chlorine atom in at least one meta position relative to the phenolic hydroxyl by hydrodechlorination of a polychlorophenol selected from the group consisting of at least one member of the group consisting of pentachlorophenol, 2,3,4,6-tetrachlorophenol, 2,3,6-trichlorophenol and 3,4-dichlorophenol,
- which process comprises
- mixing said polychlorophenol with dichlorobenzene and aluminum chloride, the molar ratio of aluminum chloride to polychlorophenol being at least 0.1 and not more than 2,
- adding hydriodic acid to the resulting polychlorophenol solution in a molar ratio of hydriodic acid to the number of chlorine atoms to be removed per molecule of polychlorophenol of between 2 and 10,
- and heating the resulting mixture at a temperature of from about 100.degree. C. to about 200.degree. C. and at a pressure of from about 5 to about 50 bars until the polychlorophenol is substantially converted and the desired metachlorophenol is formed,
- and separating the metachlorophenol from the reaction mixture.
Dependencies are inferred from the claim text.