US3528899A - Method of brominating the side chain of an alkyl benzene - Google Patents

Method of brominating the side chain of an alkyl benzene Download PDF

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Publication number
US3528899A
US3528899A US525309A US3528899DA US3528899A US 3528899 A US3528899 A US 3528899A US 525309 A US525309 A US 525309A US 3528899D A US3528899D A US 3528899DA US 3528899 A US3528899 A US 3528899A
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bromine
side chain
alkyl benzene
reaction mixture
radiation
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US525309A
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Emil Plander
Jindrich Zahalka
Viktor Formacek
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C17/00—Preparation of halogenated hydrocarbons
    • C07C17/093—Preparation of halogenated hydrocarbons by replacement by halogens
    • C07C17/10—Preparation of halogenated hydrocarbons by replacement by halogens of hydrogen atoms
    • C07C17/14—Preparation of halogenated hydrocarbons by replacement by halogens of hydrogen atoms in the side-chain of aromatic compounds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S204/00—Chemistry: electrical and wave energy
    • Y10S204/902—Production of desired compound by wave energy in presence of a chemically designated nonreactant chemical treating agent, excluding water, chloroform, carbon tetrachloride, methylene chloride or benzene
    • Y10S204/912—Oxygen treating agent
    • Y10S204/913—Peroxide agent

Definitions

  • the present invention relates to a method of brominating the side chain of an alkyl benzene and, more particularly the present invention is directed to brominating the side chain of a lower alkyl benzene such as toluene or xylene.
  • Aromatic hydrocarbons which are brominated in their side chain or side chains, such as side ehain-brominated alkyl benzenes are suitable for this purpose.
  • w,w,w,w-tetrabromoxylene, pentabromoxylene, hexabromoxylene and mixtures thereof possess properties which can be advantageously utilized in pro ducing non-inflammable synthetic materials.
  • bromine derivatives of benzene homologs which were substituted with bromine in the side chain are mainly produced by a bromination process which is activated by exposure to light, heat and organic peroxides.
  • these processes are primarily suitable only for laboratory work and not suitable for large scale industrial production of the side chain brominated products.
  • the present invention contemplates a method of brominating the side 'ice chain of an alkyl benzene, comprising the steps of forming a reaction mixture consisting essentially of an alkyl benzene and free bromine, and subjecting the reaction mixture to ionizing radiation having an energy of 0.001- 20 mev. at a dose rate of 0.5100, 0O0 rad/sec.
  • bromination in the side chain or chains of toluene, xylene and other benzene homologs may be advantageously activated by ionizing radiation derived from radioactive isotopes, X-ray radiation or accelerated electrons.
  • the ionizing alpha-, betaand gamma-radiation, the X-ray radiation and the accelerated electrons activate by interaction with the reaction mixture the substitution of the bromine radicals.
  • gamma-radiation for instance such as may be obtained from cobalt 60 or from spent fissionable materials (fuel elements) due to their wide range, i.e. due to their ability to penetrate deeply into the reaction mass. Such deep penetration, as pointed out above, cannot be obtained with light or ultraviolet rays.
  • bromination of xylene with the help of radiation proceeds in accordance with a radicalchain mechanism which can be schematically illustrated as follows:
  • the radiation bromination of xylene in the side chain is a complex reaction which comprises a series of successive reactions of the first order which may be expressed as follows:
  • the radiation bromination according to the present invention may be carried out either with individual isomers of xylene, i.e. ortho-xylene, meta-xylene or para-xylene, or with a technical mixture of these isomers.
  • ionizing radiation for activating the bromination of aromatic compounds, particularly xylene or toluene, in their side chains.
  • aromatic compounds particularly xylene or toluene
  • the physical characteristics of ionizing radiation are suitable for carrying out the bromination reaction on an industrial scale, which appeared to be not possible with prior art side chain bromination processes.
  • the above-described method for producing bromoxylene derivatives makes it possible to produce symmetric w,w,w,w'-tetrabromoxylene which is in great demand for producing self-extinguishing polystyrene foam and other macro-molecular compounds.
  • EXAMPLE II Preparation of side chain substituted monoand di-bromoxylene 26.5 grams p-xylene (0.25 mol) are introduced into a reaction vessel which is provided with a Lenard window for the entry of electrons, and 52.5 grams bromine (0.32 mol) are slowly added thereto at room temperature. An electron accelerator with an energy of 6 mev., is used as the source of radiation. The reaction mixture is intensively mixed by means of a magnetic stirring device during the entire reaction. The dose rate equals 83,300 rad/sec. The speed of introduction of bromine is controlled by the speed with which the bromine can react in the reaction mixture. 41% w-monobromoxylene and 46% w,w'-dibromoxylene are isolated from the reaction mixture.
  • reaction vessel made of glass and capable of holding 250 ml. is partly filled with 106 grams p-xylene (1 mol) and placed into a radiation chamber in Which it is subjected to radiation from a cobalt 60 source of radiation.
  • the reaction vessel is provided with a reflux cooler, heating device, conduits for introducing bromine, a dosimetric device, stirrer and conduit for withdrawing hydrogen bromide.
  • the necessary amount of bromine for instance 3 mols, 4 mols, 5 mols or 6 mols, plus a slight excess above the theoretically required amount, are introduced into the reaction vessel at such speed that no unreacted bromine will be carried along by the hydrogen bromide.
  • the number of mols of bromine depends on the desired degree of bromination of the xylene.
  • the temperature of the reaction mixture is increased during radiation in a step-Wise manner from 20 to 200 C.
  • the reaction mixture is irradiated with gamma radiation of an energy of 1.3 mev. and at a dose rate of 72 rad./ sec.
  • a yield of 65-75% of the desired bromoxylene derivative, for instance tetrabromoxylene is obtained, based on the dosimetrically introduced amount of bromine.
  • EXAMPLE -IV 106 grams of para-xylene (1 mol) having 2 grams of dibenzoyl peroxide dissolved therein are filled into a glass reaction vessel having a capacity of 250 ml. The reaction vessel is then placed inside the radiation chamber of a cobalt radiation source and equipped with a reflux cooler, a bromine supply conduit, a heating device, a dosimetric device for controlling the rate of supply of bromine, a stirrer and a hydrogen bromide discharge conduit.
  • the required quantity of bromine is dos'rmetrically introduced into the reaction vessel, for instance 3 mols, 4 mols, 5 mols or 6 mols of bromine, plus a slight excess thereover in accordance with the desired degree of broination of the final product.
  • the temperature of the reaction mixture is gradually increased to a radiation from 20 to 200 C.
  • the reaction mixture is radiated by a gamma source of 1.3 mev., the dose rate was 72 rad./ sec.
  • EXAMPLE V 106 grams of para-xylene (1 mol) are filled into a glass reaction vessel of 250 ml. capacity located within the radiation chamber of a cobalt 60 radiation source and equipped with a reflux cooler, a heating device, a :bromine supply conduit, a dosing apparatus for controlling the rate of introduction of bromine, a stirrer and a gas discharge conduit.
  • the required amount of bromine is dosimetrically introduced, for instance 3 mols, 4 mols, 5 mols or 6 mols, plus a slight excess thereover corresponding to the required degree of bromination of the final product.
  • air is bubbled through the reaction mixture at the rate of 4 liters per minute, or oxygen at the rate of 1 liter per minute.
  • the termperature of the reaction mixture is gradually increased from 20 to 200 C.
  • the reaction mixture is radiated by a gamma source of 1.3 mev., the dose rate being 72 rad./ sec.
  • the yield obtained according to Examples IV and V equals 99% of the theoretical yield calculated with respect to xylene.
  • the yield of the desired bromoxylene derivative for instance tetra-bromoxylene if slightly more than 4 mols of bromine were introduced, amounts to between and by weight based on the amount of bromine introduced into the reaction vessel.
  • reaction time was shortened in all cases by the addition of organic peroxides.
  • Organic peroxides for instance benzoyl peroxide, ditert.-butyl peroxide, ascaridol, etc., preferably are added in an amount of between 1 and 10% by weight based on the amount of xylene; or organic peroxides may be produced inthe reaction mixture by bubbling oxygen or air through the same during the course of radiation.
  • the speeding up of the reaction achieved thereby amounts to between about 10 and 15% 0f the reaction time in the absence of organic peroxides.
  • a method of brominating the side chain of an alkyl benzene comprising the steps of forming a reaction mixture of an alkyl benzene and free bromine; and subjecting said reaction mixture to ionizing radiation having an energy of 0.001- mev. at a dose rate of 0.5100,000 rad/sec.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
US525309A 1965-02-09 1966-02-07 Method of brominating the side chain of an alkyl benzene Expired - Lifetime US3528899A (en)

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AT (1) AT260209B (enEXAMPLES)
DE (1) DE1468852A1 (enEXAMPLES)
FR (1) FR1466649A (enEXAMPLES)
SE (1) SE326950B (enEXAMPLES)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2638754A1 (fr) * 1988-11-08 1990-05-11 Ciba Geigy Ag Produits ignifuges a base de composes aromatiques bromes

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2849663A1 (de) * 1978-11-16 1980-06-04 Hoechst Ag P-tert.-butylbenzotribromid und p-tert.-butylbenzoylbromid und deren am kern durch halogen substituierte derivate sowie verfahren zu ihrer herstellung
IL71576A (en) * 1984-04-19 1988-02-29 Yissum Res Dev Co Process of making ring halogenated styrenes from alpha-bromoethyl halobenzenes in the presence of a polymerization inhibitor

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1237652A (en) * 1913-07-25 1917-08-21 Cooper Hewitt Electric Co Catalytic synthesis of organic substitution products.

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1237652A (en) * 1913-07-25 1917-08-21 Cooper Hewitt Electric Co Catalytic synthesis of organic substitution products.

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2638754A1 (fr) * 1988-11-08 1990-05-11 Ciba Geigy Ag Produits ignifuges a base de composes aromatiques bromes

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DE1468852A1 (de) 1969-03-13
FR1466649A (fr) 1967-01-20
SE326950B (enEXAMPLES) 1970-08-10
AT260209B (de) 1968-02-12

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