IL32895A - Process for the preparation of pentabromophenol - Google Patents

Description

Process the of The present invention relates to process for the preparation of It is to prepare the reaction of acid with in glacial acetic The starting required for this known process has to be prepared by a separate There are involved methods which are too cumbe and complicated for a technically suitable It has been tried to convert phenol directly vith bromine into Such process has been described in the Journal of Education 20 In a tvo step process the phenol is at first converted into vhich is finely powdered iron is added to the melt as catalyst and then said is converted by the addition of further bromine into to In this process an amount of bromine times crude the theoretical has to be obtained is separated in the normal if from glacial acetic By this process the can be prepared directly however two separate steps are the great excess of bromine required is a big disadvantage as the bromine is set free only together with the hydrogen formed neously with the required end Thus a special pur step has to be added which involves a complicated apparatus and a high energy supply in order to separate hydrogen broaide the excess bromine and to obtain each of the gases in a pure conditio A further process for the production of pentabrominated aromatic compounds is known from the Patent Specif cation i 136 683 and from the Belgian Patent Specification 611 068 which corresponds partially to said German Speci According to this process the and the are with concentrated sulfuric which contains The quantity of has to be sufficient to eliminate the water formed during the reaction and to oxidize the hydrobromo acid also Following this process a product is received that contains For many purposes these products be free of therefor additional process steps are necessary to the sulphur from the products prepared by the process known in the A new process has been developed in order ro overcome the above The present invention thus consists in a process for the preparation of and gaseous hydrogen wherein phenol is reacted with in a molar ratio of up to in the presence of halogentae aliphatic carbons with carbon atoms or mixtures thereof at temperatures bromination of in the presence of a suitable Phenol is dissolved in a solvent being a halogenated aliphatic dibromoo or a mixture of two or more of such halogenated aliphatic solution is reacted after the catalyst has been with bromine passed into said As catalyst there may be for iron or aluminium powder and their or simultaneously with the phenol to the Only a small excess of about 2 to bromine is In the course of the addition of the first half of the amount of bromine to be added the temperature may be raised from about to about At the end of the bromine addition the reaction mixture is preferably heated to about After the at the end of the reaction has precipitated the excess bromine is reraoved by passing olefines such as butylene or isobutylene into the The ihalogenohydrocarbon obtained thereby may be used again as and remains in the reaction The hydrogen obtained is collected and separated from the bromine admixed therewit by conducting it through a washing tower containing acid or through another suitable washing hydrogen bromide is then obtained as pure product in an almost tical The is separated from the solvent in the usual manner washed and mother may be utilised for a new process according to the present invention overcomes the drawbacks of the known processes and enables the preparation of pentabromophenol phenol and bromine in a direct way and in a single Although only a excess of is which may be gained back nearly yields of 94 to of the theory of are The hydrogen being obtained as by product is obtained in nearly pure form ia yield without any further energy The invention will now be illustrated by the following Example without Example a reaction vessel being provided with thermometer and reflux 188 parts parts were dissolved herein are parte by of parts of 3 parts of ironjpowder were added and parts of bromine were added thereafter slowly in the course o 4 to 6 The temperature raised from room temperature to about fhe reaction proceeded at the bromine been added the temperature vas raised to the reflux temperature of about 136 to all the had been added ethylene until all the excess bromine vas disposed ascertained by observing a could hane The of and 1 vas The separated vas washed tvice w once about and then with vater until the washing vater vas free After drying at elevated temperature 920 parts of the of vere mother liquor obtained eventually after the addition of nev utilised in a Thereby the yield could be raised in the batches up to of the obtained hydrogen bromide passed containing vas through a washing about phosphorousacid whereby the bromine residues therewith vere 800 parts of hydrogen vere obtained which corresponds to an almost insufficientOCRQuality

Claims (1)

1. 6 for the preparation of and gaseous hydrogen wherein phenol is reacted with bromine in a ratio of ls5 up to in the presence of aliphatic hydrocarbons with carbon atoms or mixtures thereof at of the bromination presence of a suitable Process according to wherein the excess bromine is after the end of the reaction by the addition of and the obtained remains in the mother liquor as Process according to or wherein the solvent is selected among the group consisting of or or fixtures Process for the preparation of pentabrorsophenol and gaseous hydrogen substantially as hereinbefore described with reference to the whenever prepared by the process according to any of Claims 1 to Gaseous hydrogen bromide whenever prepared by the process according to any of Claims 1 to For the Applicants Yitzhak insufficientOCRQuality