IL44080A - Preparation of brominated aromatic compounds - Google Patents

Description

The preparation of aromatic compounds PRODUITS 41930 our Israel Patent Specification 33048 we hav described a known as forced for the bromination o the ring of aromatic compounds having a high melting This technique consists carrying out the in a heterogeneous medium by means of elementary bromine and in the absence of solvent in a reactor equipped with a su power mixing device to ensure mixing and agitation of the whole of the reaction mixture during the entire duration of the Continuing ou studies in this we have found that it was possible to use a technique which made useo an entirely known by introducing the product to be at the beginning a certain quantity of which plays the part both of reagent and of and possibly a halogenation catalysts According to the present invention there is provided a process for the of aromatic compounds using elementary bromine at a temperature lower than whereby the bromine atoms are attached to the aromatic comprising gradually introducing either the product to be brominated or the product to be and a part of the bromine necessary for the reaction into a reactor previously charged with the quantity of bromine present being maintained throughout the reaction at a minimum excess of with respect to the quantity stoichiometrically necessary for the reactiono The bromination reaction is carried out without difficulty at a temperature lower than for example at temperature a slight accelerating the and the best yields are obtained with an excess of bromine of at least of the bromine stoichiometrically and preferably 40 to The bromination process of the invention is quite general and may be used for all bromination reactions t has been found particularly interesting for the romination of aromatic compounds Which are normally difficult to such as the the diphenyl oxide and phenylene as well the derivatives of these various Furthermore it frequently useful in the case of to use catalysts as iron aluminium halideso advantages of the process of the invention are reduction of risks of corrosion due to the use of materials which cann t be therefore obtaining products which are the absence of which makes it possible to use a reactor of smaller dimensions for an equal rate production and it does not risk involving participation of the solvent itself in the ating a costly recovery and purificatio Furthermore the bromination can be carried out at ambient temperature or slightly elevated temperature and leads to high The bromination according to the process of the invention may be carried out either by directly placing into the reactor the whole of the bromine to be then introducing agitation the product to be or by placing the reactor a certain quantity of the bromine necessary and the introducing with agitation the product to be brominated the one hand and the additional quantity of bromine on the the respective quantities of the one and the ether being such that an excess of bromine of at least 20 in relation to the quantity stoichiometrically necessary is maintained throughout the The bromination is followed by the separation of the derivative obtained and its purification by known A convenient which has advantage of possible to carry out the entire bromination and purification operation in the same apparatus is conversion of the excess of bromine remaining at the end of the reaction into hane by the injection of This latter used h a suitable makes it possible to continuous as is show Example 10 The invention no be further with referenc to the following EXAMPLE 1 The operation as carried ou in glass reacto 1 litre equipped with a temperature a heated retained by the decabromobiphenyl into hydrobromic After mixture was dried in an enamelled dryer with cotton then rinsed abundantly water and dried in an for 4 540 g of pure decabromodiphenyl with a melting point of hich corresponds to a yield were 2 800 g o bromine and of anhydrous chloride were placed into the same apparatus as in Example Ove 1 hour there were gradually added at ambient temperature g of a molten mixture of isomeric After the end of addition it was heated fo 1 hour at At the end this additio there had bee in the water absorber 235 of hydrobromic acid and 65 g of bromine The reaction mixture consisted of a suspension of approximately 280 g of tetradecabromoterphehyl in 270 of bromine This produce was purified as described Example 1 and there finally obtained 250 g of very light beige powder a melting point of EXAMPLE 3 the same apparatus as that described in Example there were placed 800 g of bromine and g of aluminium Over hour there were gradually added 51 g of molten diphenyl At the of the had been in the absorber 2 g of hydrobromic acid 95 and 42 g of entrained eaction mixture was a suspension of 285 g of decabromodiphenyl ether in 2δ0 g of bromine moles The decabromodiphenyl ether was purified by the process described in Example 1 and there were finally obtained 285 g of dry product taking the form of a white powder a melting point of Into the same apparatus as that described in Example 1 were placed g of bromine 4 g of anhydrous aluminium chloride Over hour minutes there were poured in at ambient temperature 182 g of a mixture of benzenes rich in obtained by the pyrolysis of hexaehlorocyclohexane After end of the addition it was heated for 1 hour at At the end of the heating there had been collected in the water absorber 240 g of hydrobromic acid and 32 g of entrained The refrigerator had been cooled to in this experimen he excess of bromine was separated by as in Example the obtained was finally washed with 1100 g of a acid solution for 1 hour at injecting during the washing approximately 16g of sulphur dioxide 5 so as to reduce the bromine adsorbed by the e a whi powder with a melting point of which corresponds to a yield of EXAMPLE 5 In the same apparatus as that described in Example 1 one places 800 g 5 of bromine and 5 g of anhydrous aluminium Over 1 hour 55 2 g 0 6 of toluene were passed into the It was then heated for 1 hour at There had then been collected in the water absorber 235 g 9 of liydrobromic acid and 45 g 28 of entrained he product was purified under the same conditions as those described in Example There were finally obtained 285 g of pentabromotulene a white powder with a melting point of which corresponds a yield of EXAMPLE 6 to same apparatus as that described in Example 1 were placed 800 g 5 of bromine and 5 g of iron Over 1 hour there were poured in 5 g 6 of molten It was then heated for 1 hour at There had then been collected in the water absorber 240 g 95 of hydro acid and 5 g 28 of entrained The obtained was separated and purified under the conditions described in Example There were obtained 260 g of dry pentabromophenol which takes the form of a light beige powder with a melting point of which corresponds to a yield of Into the same apparatus as that described in Example 1 1280 g of 5 g of aluminium Over 1 hour there were added 76 g of molten The mixture was heated for I hours at There had then been collected in the water absorber 340 g of h drobromic acid and 130 g of entrained The product was purified according to the process described in Example There were finally obtained 325 g of a product which the form of a light coloured powder with a melting point of 260 the bromine content of corresponds a heptabro 8 In the same apparatus as that described in 1 there were prepared under the same conditions as those of Exampl 1 a suspension consis ng of g of decabromobiphenyl 6 i 50 of After the end of the reaction there were added to this suspension 570 g of 1 then there were injected whilst cooling 80 g of ethylene over a period of 2 whilst maintaining the temperature of the reaction medium at about After the of this addition there were added g of hydrochloric acid and the mixture heated for 1 hour at accompanied by vigorous After it was filtered on an enamelled dryer abundantly ri with wa dr ing e directly 522 g o very pure a white a melting point in the vicinity of and which corresponds to a yield of There were obtained 480 g of a with a yield of By recycling dibromoethane there was obtained an increase in the yield of decabromobiphenyl o approximately EXAMPLE 9 Under the same conditions as in Example 3 a suspension o 285 g of decabromodiphenyl ether in 280 g bromine was The purification was carried out under the same conditions as in Example 8 after the addition 300 g of by the injection over 2 hours under of 56 g of and then washing at for hour with 650 of a hydrochloric acid After rinsing with water and drying there were obtained 275 g of decabromodiphenyl a white powder with a melting point and 295 g of as EXAMPLE 10 Under the same conditions as in Example a suspension of 565 g of in 496 g moles of bromine was After the end of the reaction suspension was passed gradually through a vertical falling film evaporator with a stainless steel this apparatus being heated to by a stream of hot water flowing inside the double The bromine was then condensed in a crude decabromoblphenyl was recovered the form of powder at the of the At the end the which lasted two there were obtained g of crude decabromoblphenyl containing approximatel 1 g of aluminium in the form of bromide and 36 g of adsorbed and 454 g of bromine which could be without additional The crude product thus obtained was purified by escribed in Example 1 and there were finally obtained 537 g of decabromobiphehyl with a melting point of 11 Into the reacto described in Example and equipped with second feed flask were placed kg of bromine 5 g of arihydrdus aluminium Over a period 1 hour there were gradually accompanied by vigorous g of molten biphenyl and kg of The reaction was then under the same conditions as used in Example There were obtained 530 of pure biphenyl with a melting point of which corresponds a yield of insufficientOCRQuality

Claims (1)

1. What we Claim is: - . lo A process for 'the bromination of aromatic compounds L using elementary bromine at a temp rature lower than 70°C whereby the bromine atoms are attached to the aromatic ring, comprising gradually introducing either the product to be brominated or the product to be brominated and a part of the bromine necessary for the reaction into a reactor previously charged with bromine, the quantity of bromine present being maintained throughout the reaction at a minimum excess of 20^ with respect to the quantity stoichiometrically necessary for the reaction. ' > ■ 2« A process according to Claim 1, wherein the bromineition is carried out in the presence of a halogenation catalyst chosen from iodine, the halides of iron or the halidss of aluminium. " 3· A process according to Claim 1 or 2, wherein the bromination is carried out with an excess of bromine of between 40 and JOfi of the quantity of bromine stoichiometricall necessary for the reaction.. I \ 4o A process for the bromination of aromatic compounds substantiall as hereinbefore described with reference to any one of Examples 1 to 11. 5o An aromatic compound carrying bromine atoms on the i aromatio ring produced by the process of any one of Claims 1 to