GB1563164A - , -dihaloethylaromatic compounds - Google Patents

, -dihaloethylaromatic compounds Download PDF

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GB1563164A
GB1563164A GB4714577A GB4714577A GB1563164A GB 1563164 A GB1563164 A GB 1563164A GB 4714577 A GB4714577 A GB 4714577A GB 4714577 A GB4714577 A GB 4714577A GB 1563164 A GB1563164 A GB 1563164A
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moles
chlorine
alpha
reaction
dichloroethylbenzene
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Euteco SpA
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Euteco SpA
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C253/00—Preparation of carboxylic acid nitriles
    • C07C253/30—Preparation of carboxylic acid nitriles by reactions not involving the formation of cyano groups
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
    • C07B39/00—Halogenation
    • 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

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Description

(54) IMPROVEMENTS IN OR RELATING TO a,a DIHALOETHYLAROMATIC COMPOUNDS (71) We, EUTECO S.p.A., an Italian Joint Stock Company, of 11, Via Galiani, Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a process for the preparation of a, a- dihaloethylaromatic compounds, defined by the general formula:
by means of the chlorination or bromination of the corresponding mono-halogenated compounds:
where X is chlorine or bromine; R, R' and R" are groups as hereinafter defined which are inert (non reactive) under the chlorination or bromination conditions.
The compounds of general formula (I) may be converted into those definable by the formula:
Thus, for example, a-chlorostyrene can be produced by dehydrochlorination of a,a- dichloroethylbenzene and can be used in the manufacture of graft copolymers.
Moreover, a-fluorostyrene can be produced from a,-dichloroethylbenzene.
or else from a-chlorostyrene by treatment with hydrogen fluoride.
Further, in the case of R being hydrogen, the compounds of general formula (I) can be converted into those defined by the formula:
Thus, for example, phenylacetylene can be produced by dehydrochlorination of a- chlorostyrene, the latter being, in its turn, produced by dehydrochlorinating a,adichloroethylbenzene. The said phenylacetylene may be polymerised to give a stabiliser useful in polyvinyl chloride compositions.
In the halogenation of compounds of the general formula (II) there are difficulties in directing the reaction towards the desired products of formula (I).
In fact the best selectivities for the a,a- dihalogenated derivatives are achieved only at temperatures so low as to render the method impracticable on a commercial scale, because of the low rates of halogenation.
On the other hand, in the temperature range in which the reaction rate is higher, dehydrohalogenation of the a,adihalogenated derivatives occurs very easily, with consequent formation of the corresponding unsaturated compounds, which interact in their turn with the halogen, giving rise to derivatives with a higher degree of halogenation.
In conclusion, high consumption of halogen occurs and by-products are formed in relatively large quantities.
The drawbacks of the prior art are overcome. or at least greatly reduced, by the process of the present invention which is based essentially on the use of one particular catalytic system for the halogenation of the compounds of general formula (II), at low temperatures and with high reaction rates.
Thus, according to the present invention there is provided a process for the preparation of ,r,ct-dihaloethylaromatic compounds of the formula:
by chlorination or brornination of cr-haloethylaromatic compounds of the formula:
where X is chlorine or bromine, R and R' independently are hydrogen, fluorine or a cyano, aryl, perhaloalkyl or tertiary alkyl radical. and R" is chlorine, fluorine, bromine, iodine, hydrogen or a phenoxy, phenylalkoxy, cyano or tertiary alkyl radical, which process comprises reacting said cr-haloethylaromatic compound, either in the liquid form or dissolved in an organic solvent which cannot be halogenated under the reaction conditions, with gaseous chlorine or bromine added in an amount corresponding to a molar ratio between the -haloethylaromatic compound and halogen of from 10:1 to 1:1, at a temperature of from 0" to 1000C, in the presence of a phosphorus halide catalyst, and white light and/or an activator capable of generating free radicals under the reaction conditions, and recovering the a,a-dihaloethylaromatic compound thus obtained from the reaction product.
The compound of formula (II) may, for example. be chosen from ahaloethylbenzenes, p-perhaloalkyl-a- haloethylbenzenes, A-tert-butyl-a- haloethylbenzenes, p,p-di-tert-hexyl-a- haloethylbenzenes, p-cyano-a- haloethylbenzenes, W3-aryl-Cz- haloethylbenzenes, i3-A-diaryl-cr- haloethylbenzenes, o-, m-, or p-tert-alkyl-a- haloethylbenzenes and o-, m-. or p-halo-a- haloethylbenzenes.
The compounds which are preferred, in view of their ready commercial availability, are a-haloethylbenzenes corresponding to the general formula (II) where R and R' are hydrogen and R" is either hydrogen or fluorine, chlorine, bromine or a tertiary butyl group.
Amongst all these, a-haloethylbenzenes, which are easily made by the hydrohalogenation of styrene in the a- position at low temperatures (from -1000C to 0 C) are particularly preferred.
As has been stated, the reaction is carried out in the liquid phase with the compound of formula (II), either liquid or in organic solution.
Organic solvents which are suitable for the purpose are those which dissol e the compound to be halogenated and which do not undergo halogenation under the reaction conditions, such as benzene, carbon tetrachloride. mono- and poly chlorobenzenes. nitrobenzeres, benzoniti ile.
The molar ratio between the compound of formula (11) and the halogen is preferably from 1.4:1 to 2:1.
Under these conditions it is in fact possible to obtain a selectivity for the a,a- dihalogenated derivative of the order of from 80 to 90 ", the other conversion products consisting essentially of cy,J3- dihalogenated derivatives which may also be used in practice.
The halogenation temperature is preferably from 200C to 50"C. In fact.
below 20"C the reaction speed tends to diminish, whereas above 50"C the phenomena of dehydrohalogenation referred to above begin to occur.
The phosphorus halide catalyst is preferably chosen from phosphorus pentachloride, phosphorus pentabromide, and phosphorus tribromide or trichloride.
The halogenation catalyst is advantageously used in an amount of from 0.1 to 5 E by weight with respect to the weight of the compound to be halogenated.
and preferably in an amount of the order of 0.5";, by weight.
The activator is preferably chosen from peroxides and percarbonates which decompose at the halogenation temperature, such as, for example.
isopropyl percarbonate, 2,4dichlorobenzoyl peroxide, benzoyl peroxide, lauroyl peroxide and decanoyl peroxide, or else non-peroxide substances which are nevertheless capable of initiating radical reactions, such as lt,(F azobisisobutyronitrile.
The said activator is preferably used in an amount of from 0.1 to 1% by weight based on the weight of the compound to be halogenated, the molar ratio between the said catalyst and the said activator being advantageously from 1:1 to 10:1.
The use of the said catalytic system in the halogenation of compounds of formula (II) can result in: considerable acceleration of the rate of halogenation within the said temperature range, increased selectivity of halogenation in the a position, and inhibition or at least minimising of secondary reactions of halogenation of the aromatic ring, bearing in mind the fact that the said het ondarn reactions occur cspeciallv xnhen R" is an electrondonor group.
The said activator is preferably used onlv uhen the halogenation reaction is carried out in the dark. It is in fact preferable to use white light alone in lieu of the activator when the halogenation reaction is not carried out in the dark.
In practice, the reaction is preferably carried out as follows: Weighed quantities of the compound of formula (II) and of the catalyst for the halogenation are placed in a glass reactor.
A flow of nitrogen is then passed through the reactor to remove oxygen which is a known radical inhibitor, and the halogen is bubbled through the reaction mass, while keeping the latter under agitation and at the preselected temperature.
When a peroxide activator is used, the reactor is dimmed bq enveloping it. for example, in aluminium foil.
At the end of the reaction the compound of formula (II) is recovered by conventional methods, such as, for example, distillation at subatmospheric pressure. The following examples further illustrate the present invention.
EXAMPLE I 50 grams (0.352 moles) of a- chloroethylbenzene (prepared by hydrochlorination of styrene at -30 C) and 0.5 grams of phosphorus pentachloride are placed in a cylindrical glass reactor with a diameter of 3.5 cm.
The reactor is supplied with a bubbler for the chlorine, a magnetic agitator, and a breather pipe for the hydrogen chloride and any unreacted chlorine.
The reactor is placed in a bath thermostatically regulated to 30"C, and, after it has been purged with nitrogen, 0.18 moles of chlorine are introduced over a period of about 2 hours.
Analysis of the reaction products shows that 0.15 moles of chlorine and 0.139 moles of i-chloroethylbenzene were converted.
The products of the conversion of the latter are distributed as follows: 0.1 moles of .e,-dichloroethylbenzene: 0.012 moles of cu.p-dichloroethylbenzene: 0.004 moles of a,a,- trichloroethylbenzene.
EXAMPLE 2 The run of Example 1 is repeated at a reaction temperature of 40 C, 0.185 moles of chlorine being fed in.
0.179 moles of chlorine and 0.177 moles of (E-chloroethylbenzene are converted.
The conversion products of the latter are distributed as follows: 0.158 moles of α,α-dichloroethylbenzene: 0.015 moles of a,;3-dichloroethylbenzene: n.ooa moles of α,α, - trichloroethylbenzene.
EXAMPLE 3 The run of Example 1 is repeated at a reaction temperature of 60 C, 0.198 moles of chlorine being fed in.
0.191 moles of chlorine and 0.16' moles of -chloroethylbenzene are converted.
The conversion products of the latter are distributed as follows: 0.096 moles of tr,(u-dichloroethylbenzene: 0.030 moles of n,p-dichloroethylbenzene: 0.013 moles of α-chlorostyrene; 0.013 moles of (u,a,P- trichloroethylbenzene; 0.010 moles of α,α, , - tetrachloroethylbenzene.
EXAMPLE 4 The procedure is the same as in Example the reaction temperature being 300C as in Example 1 and the reactor being enveloped in aluminium foil so as to insulate it against light.
50 grams of a-chloroethylbenzene, 0.5 grams of phosphorus pentachloride and 0.5 grams of lauroyl peroxide are loaded into the reactor and 0.198 moles of chlorine are fed in.
0.916 moles of chlorine and 0.190 moles of a-chloroethylbenzene are converted.
The conversion products of the latter are distributed as follows: 0.158 moles of a,a-dichloroethylbenzene; 0.016 moles of a,p-dichloroethylbenzene: 0.007 moles of a,a,b- trichloroethylbenzene: 0.008 moles of α,α, , - tetrachloroethylbenzene.
COMPARATIVE EXAMPLE 5 50 grams (0.472 moles) of ethylbenzene and 0.5 grams of phosphorus pentachloride are loaded into the reactor of Example 1.
The reaction is carried out at a temperature of 40"C, 48.4 grams (0.679 moles) of chlorine being fed in over about 2 hours.
The chlorine/ethylbenzene molar ratio is thus 1.45:1.
0.672 moles of chlorine are converted and the conversion products of ethylbenzene are distributed as follows: 0.275 moles of a-chloroethylbenzene; 0.148 moles of a,a-dichloroethylbenzene; 0.032 moles of cw"B-dichloroethylbenzene; 0.010 moles of α,α, - trichloroethylbenzene; 0.005 moles of a,a,,- tetrachloroethylbenzene.
WHAT WE CLAIM IS: 1. A process for the preparation of a,a-
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

  1. **WARNING** start of CLMS field may overlap end of DESC **.
    the said het ondarn reactions occur cspeciallv xnhen R" is an electrondonor group.
    The said activator is preferably used onlv uhen the halogenation reaction is carried out in the dark. It is in fact preferable to use white light alone in lieu of the activator when the halogenation reaction is not carried out in the dark.
    In practice, the reaction is preferably carried out as follows: Weighed quantities of the compound of formula (II) and of the catalyst for the halogenation are placed in a glass reactor.
    A flow of nitrogen is then passed through the reactor to remove oxygen which is a known radical inhibitor, and the halogen is bubbled through the reaction mass, while keeping the latter under agitation and at the preselected temperature.
    When a peroxide activator is used, the reactor is dimmed bq enveloping it. for example, in aluminium foil.
    At the end of the reaction the compound of formula (II) is recovered by conventional methods, such as, for example, distillation at subatmospheric pressure. The following examples further illustrate the present invention.
    EXAMPLE I
    50 grams (0.352 moles) of a- chloroethylbenzene (prepared by hydrochlorination of styrene at -30 C) and 0.5 grams of phosphorus pentachloride are placed in a cylindrical glass reactor with a diameter of 3.5 cm.
    The reactor is supplied with a bubbler for the chlorine, a magnetic agitator, and a breather pipe for the hydrogen chloride and any unreacted chlorine.
    The reactor is placed in a bath thermostatically regulated to 30"C, and, after it has been purged with nitrogen, 0.18 moles of chlorine are introduced over a period of about 2 hours.
    Analysis of the reaction products shows that 0.15 moles of chlorine and 0.139 moles of i-chloroethylbenzene were converted.
    The products of the conversion of the latter are distributed as follows: 0.1 moles of .e,-dichloroethylbenzene: 0.012 moles of cu.p-dichloroethylbenzene: 0.004 moles of a,a,- trichloroethylbenzene.
    EXAMPLE 2 The run of Example 1 is repeated at a reaction temperature of 40 C, 0.185 moles of chlorine being fed in.
    0.179 moles of chlorine and 0.177 moles of (E-chloroethylbenzene are converted.
    The conversion products of the latter are distributed as follows: 0.158 moles of α,α-dichloroethylbenzene: 0.015 moles of a,;3-dichloroethylbenzene: n.ooa moles of α,α,ss- trichloroethylbenzene.
    EXAMPLE 3 The run of Example 1 is repeated at a reaction temperature of 60 C, 0.198 moles of chlorine being fed in.
    0.191 moles of chlorine and 0.16' moles of -chloroethylbenzene are converted.
    The conversion products of the latter are distributed as follows: 0.096 moles of tr,(u-dichloroethylbenzene: 0.030 moles of n,p-dichloroethylbenzene: 0.013 moles of α-chlorostyrene; 0.013 moles of (u,a,P- trichloroethylbenzene; 0.010 moles of α,α,ss,ss- tetrachloroethylbenzene.
    EXAMPLE 4 The procedure is the same as in Example the reaction temperature being 300C as in Example 1 and the reactor being enveloped in aluminium foil so as to insulate it against light.
    50 grams of a-chloroethylbenzene, 0.5 grams of phosphorus pentachloride and 0.5 grams of lauroyl peroxide are loaded into the reactor and 0.198 moles of chlorine are fed in.
    0.916 moles of chlorine and 0.190 moles of a-chloroethylbenzene are converted.
    The conversion products of the latter are distributed as follows: 0.158 moles of a,a-dichloroethylbenzene; 0.016 moles of a,p-dichloroethylbenzene: 0.007 moles of a,a,b- trichloroethylbenzene: 0.008 moles of α,α,ss,ss- tetrachloroethylbenzene.
    COMPARATIVE EXAMPLE 5
    50 grams (0.472 moles) of ethylbenzene and 0.5 grams of phosphorus pentachloride are loaded into the reactor of Example 1.
    The reaction is carried out at a temperature of 40"C, 48.4 grams (0.679 moles) of chlorine being fed in over about 2 hours.
    The chlorine/ethylbenzene molar ratio is thus 1.45:1.
    0.672 moles of chlorine are converted and the conversion products of ethylbenzene are distributed as follows: 0.275 moles of a-chloroethylbenzene; 0.148 moles of a,a-dichloroethylbenzene; 0.032 moles of cw"B-dichloroethylbenzene; 0.010 moles of α,α,ss- trichloroethylbenzene; 0.005 moles of a,a,,- tetrachloroethylbenzene.
    WHAT WE CLAIM IS: 1. A process for the preparation of a,a-
    dihaloethvlaromatic compounds of the formula:
    bv chlorination or bromination of ahaloethylaromatic compounds of the formula:
    where X is chlorine or bromine, R and R' independently are hydrogen, fluorine or a cyano, aryl, perhaloalkyl or tertiary alkyl radical, and R" is hydrogen, chlorine, fluorine, bromine, iodine or a phenoxy, phenylalkoxy, cyano or tertiary alkyl radical, which process comprises reacting said cr-haloethylaromatic compound, either in the liquid form or dissolved in an organic solvent which cannot be halogenated under the reaction conditions, with gaseous chlorine or bromine added in an amount corresponding to a molar ratio between the a-haloethylaromatic compound and halogen of from 10:1 to 1:1, at a temperature of from 0 to 100"C, in the presence of a phosphorus halide catalyst, and white light and/or an activator capable of generating free radicals under the reaction conditions, and recovering the a,a-dihaloethylaromatic compound thus obtained from the reaction product.
  2. 2. A process according to claim 1, in which said a-haloethylaromatic compound is a a-haloethylbenzene.
  3. 3. A process according to claim 1 or 2, in which said molar ratio between a- haloethylaromatic compound and halogen is from 2:1 to 1.4:1.
  4. 4. A process according to any one of the preceding claims, in which the reaction temperature is from 20C to 50"C.
  5. 5. A process according to any one of the preceding claims, in which said catalyst is present in an amount of from 0.1 to 5% by weight with respect to the ahaloethylaromatic compound.
  6. 6. A process according to any one of the preceding claims, in which said phosphorus halide is chosen from phosphorus trichloride, tribromide, pentachloride and pentabromide.
  7. 7. A process according to any one of the preceding claims, in which said activator is present in an amount of from 0.1 to 1% by weight with respect to the a- haloethylaromatic compound.
  8. 8. A piocess according to any one of the preceding claims, in which the molar ratio between said catalyst and said activator is from 1:1 to 10:1.
  9. 9. A process according to any one of the preceding claims, in which said activator is chosen from peroxides, percarbonates and a,a-azobisisobutyronitrile.
  10. 10. A process according to claim 1, substantially as hereinbefore described with reference to any one of Examples 1 to 4.
  11. 11. a,a-dihaloethylaromatic compounds, whenever obtained by the process according to any one of claims 1 to 10.
GB4714577A 1976-11-19 1977-11-11 , -dihaloethylaromatic compounds Expired GB1563164A (en)

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IT2954276A IT1125157B (en) 1976-11-19 1976-11-19 PROCEDURE FOR THE PREPARATION OF COMPOUNDS, '- ETHYLAROMATIC DIALOGEN

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3813453A1 (en) * 1987-04-24 1988-11-03 Central Glass Co Ltd NEW BISBENZOTRIFLUORIDE DERIVATIVES AND METHOD FOR THEIR PRODUCTION
US4992151A (en) * 1990-01-29 1991-02-12 The Dow Chemical Company Method for the selective alpha halogenation of alkylaromatic compounds
US5064518A (en) * 1990-01-29 1991-11-12 The Dow Chemical Company Method for the selective alpha halogenation of alkylaromatic compounds
WO2011073703A3 (en) * 2009-12-16 2011-08-11 Sanofi Process for the preparation of 4-bromomethyl-[1,1'-biphenyl]-2'-carbonitrile
CN111825520A (en) * 2020-07-27 2020-10-27 西安思科赛实业有限公司 Preparation process of alpha, alpha' -tetrachloro-o-xylene

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3813453A1 (en) * 1987-04-24 1988-11-03 Central Glass Co Ltd NEW BISBENZOTRIFLUORIDE DERIVATIVES AND METHOD FOR THEIR PRODUCTION
US4992151A (en) * 1990-01-29 1991-02-12 The Dow Chemical Company Method for the selective alpha halogenation of alkylaromatic compounds
US5064518A (en) * 1990-01-29 1991-11-12 The Dow Chemical Company Method for the selective alpha halogenation of alkylaromatic compounds
WO2011073703A3 (en) * 2009-12-16 2011-08-11 Sanofi Process for the preparation of 4-bromomethyl-[1,1'-biphenyl]-2'-carbonitrile
CN111825520A (en) * 2020-07-27 2020-10-27 西安思科赛实业有限公司 Preparation process of alpha, alpha' -tetrachloro-o-xylene

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