Process for the monohalogenation of alkylbenzenes in the .alpha.-position and new alkylbenzenes monohalogenated in the .alpha.-position

A process for the monohalogenation of alkylbenzenes in the .alpha.-position is disclosed wherein an alkylbenzene reactant containing a hydrogen atom in the .alpha.-position is contacted with a halogen and the reaction mixture is withdrawn such that the amount of monohalogenated alkylbenzene formed is no greater than 33 mol percent in the reaction mixture. Also disclosed are novel monohalogenated alkylbenzenes of the formula ##STR1## in which R.sup.7 represents trifluoromethoxy, trifluoromethylthio or 2-perfluoropropyl or also, if R.sup.8 represents chlorine, represents trifluoromethyl and, furthermore, if PA1 R.sup.8 and R.sup.9 represent trifluoromethyl, represents hydrogen, PA1 R.sup.8 represents hydrogen or also, if R.sup.7 represents trifluoromethyl or trifluoromethoxy, represent chlorine and also, if R.sup.7 represents hydrogen and R.sup.9 represents trifluoromethyl, denotes trifluoromethyl and PA1 R.sup.9 represents hydrogen and, if R.sup.7 represents hydrogen and R.sup.8 represents trifluoromethyl, denotes trifluoromethyl.

BACKGROUND OF THE INVENTION 
Field of the Invention 
The invention relates to a process for the monohalogenation of 
alkylbenzenes in the .alpha.-position and to new alkylbenzenes 
monohalogenated in the .alpha.-position. 
Discussion of Prior Art 
It is known to chlorinate alkylbenzenes, for example toluene, in the side 
chain with elementary chlorine at elevated temperature and with exposure 
to UV light. By-products are formed in this reaction, for example benzal 
chloride, benzotrichloride, products chlorinated in the nucleus and 
condensed, high-boiling by-products are additionally formed when toluene 
is chlorinated to benzyl chloride (Houben-Weyl, Methoden der organischen 
Chemie (Methods of Organic Chemistry), volume V/3, page 736, Georg Thieme 
Verlag Stuttgart, 1962). 
SUMMARY OF THE INVENTION 
A process for the monohalogenation of alkylbenzenes in the .alpha.-position 
has been found which is characterised in that an excess of an alkylbenzene 
which has at least one hydrogen atom in the .alpha.-position and which 
optionally contains water up to saturation concentration, is reacted 
continuously with a halogen in the temperature range of about 80.degree. 
C. up to the boiling point of the alkylbenzene employed and in the 
presence of light containing UV radiation, the halogenation being carried 
out to an extent such that the concentration of the halogenoalkylbenzene, 
newly formed by monohalogenation, in the reaction mixture continuously 
withdrawn from the reaction space is not more than about 33 mol %, 
relative to the number of mols of all of the substances contained in the 
reaction mixture. 
Examples which can be mentioned of alkylbenzenes which have at least one 
hydrogen atom in the .alpha.-position are those of the formula 
##STR2## 
in which 
R.sup.1 to R.sup.5 can be identical or different and represent hydrogen, 
alkyl, halogenoalkyl, aryl, aralkyl, alkoxy, aryloxy, halogen, isocyanate, 
nitro, chlorosulphonyl, chlorocarbonyl or cyano and, in addition, two 
adjacent radicals R.sup.1 to R.sup.5 together can form an alkylene group, 
or together with the carbon atoms which carry them can represent a fused 
aromatic ring, and 
R.sup.6 denotes hydrogen, halogen, alkyl or aryl. 
Examples of alkyl which may be mentioned are straight-chain or branched 
hydrocarbon radicals with 1 to 4 carbon atoms, such as methyl, ethyl, 
propyl, isopropyl, butyl or isobutyl. The preferred alkyl is the methyl 
radical. 
Examples which may be mentioned of halogenoalkyl are partially or 
completely halogenated straight-chain or branched hydrocarbon radicals 
with 1 to 4 carbon atoms, such as chloromethyl, dichloromethyl, 
trichloromethyl, bromomethyl, dibromomethyl, tribromomethyl, 
monofluoromethyl, difluoromethyl, trifluoromethyl, 
monofluorodichloromethyl, difluoromonochloromethyl, partially or 
completely halogenated ethyl radicals, partially or completely halogenated 
propyl radicals and partially or completely halogenated butyl radicals. 
The trichloromethyl radical and the trifluoromethyl radical are preferred 
halogenoalkyl. 
Examples which may be mentioned of aryl are aromatic radicals with 6 to 14 
carbon atoms, such as phenyl, naphthyl, anthryl or diphenyl. The preferred 
aryl is phenyl. 
Examples which may be mentioned of aralkyl are hydrocarbon radicals with 1 
to 2 carbon atoms in the aliphatic part and 6 to 14 carbon atoms in the 
aromatic part, such as benzyl, .beta.-phenyl-ethyl, naphthyl-methyl, 
naphthyl-ethyl, anthryl-methyl, anthryl-ethyl, ortho-, meta- and 
para-diphenyl-methyl and ortho-, meta- or para-diphenyl-ethyl. 
The preferred aralkyl is the benzyl radical. 
Examples which may be mentioned of alkoxy are radicals which are derived 
from a C.sub.1 -C.sub.4 alcohol, such as methoxy, ethoxy, propoxy, 
isopropoxy, butoxy or isobutoxy. The preferred alkoxy is the methoxy 
radical. 
Examples which may be mentioned of aryloxy are radicals which are derived 
from a phenolic compound such as phenoxy, diphenyloxy, napthyloxy or 
anthryloxy i.e. from 6 to 18 carbocyclic carbon atoms. The preferred 
aryloxy is the phenoxy radical. 
The elements fluorine, chlorine, bromine or iodine, preferably fluorine, 
chlorine or bromine, can be the halogen. 
If two adjacent radicals R.sup.1 to R.sup.5 together form an alkylene 
group, alkylene groups which can be formed are those with 3 to 4 carbon 
atoms, which optionally can carry further lower alkyl radicals, for 
example trimethylene, methyl-substituted trimethylene, tetramethylene or 
methyl-substituted tetramethylene. 
Furthermore, two adjacent groups R.sup.1 to R.sup.5, together with the 
carbon atoms which carry them, can represent a fused aromatic ring, so 
that, including the aromatic ring which carries the substituents R.sup.1 
to R.sup.5, for example the naphthalene system forms. 
Examples which may be mentioned of starting compounds of the formula (I) 
for the process according to the invention are: toluene, ortho-xylene, 
meta-xylene, para-xylene, mesitylene, durol, 1,2,4-trimethylbenzene, 
pentamethylbenzene, hexamethylbenzene, ortho-chlorotoluene, 
meta-chlorotoluene, para-chlorotoluene, ortho-fluorotoluene, 
meta-fluorotoluene, para-fluorotoluene, ortho-bromotoluene, 
meta-bromotoluene, para-bromotoluene, ortho-cyanotoluene, 
meta-cyanotoluene, para-cyanotoluene, dichlorotoluene, trichlorotoluene, 
difluorotoluene, trifluorotoluene, ortho-phenoxytoluene, 
meta-phenoxytoluene, para-phenoxytoluene, phenoxy-chlorotoluene, 
phenoxy-fluorotoluene, ortho'-, meta'- and para'-chloro-phenoxytoluene, 
ortho'-, meta'- and para'-fluorophenoxytoluene, methylnaphthalene, 
methylbiphenyl, tetrafluorotoluene, pentafluorotoluene, ortho-, meta- and 
para-nitrotoluene; ortho-, meta- and para-chlorosulphonyltoluene, benzyl 
chloride, and all the isomeric toluenes substituted in the benzene nucleus 
by chlorine and fluorine, by bromine and fluorine and by iodine and 
fluorine. 
An example of an excess of the starting materials of the formula (I) 
relative to the halogen is a ratio of 2 to 50 mols and preferably 3 to 20 
mols of alkylbenzene of the formula (I) per mol of halogen. 
The starting materials of the formula (I) can be employed in the process 
according to the invention in the form of anhydrous substances. However, 
it has been found that water-containing substances of the formula (I) can 
also be employed without impairing the reaction in the process according 
to the invention. An example of the water content which may be mentioned 
is a water content of up to saturation concentration. 
An example of halogenation of the starting materials of the formula (I) in 
the process according to the invention is the reaction with chlorine or 
bromine. The reaction with chlorine is preferred. 
In the process according to the invention, the halogen is introduced as a 
gas into the reaction space. The halogen can be employed without further 
diluent, but one can also dilute the gaseious halogen with inert gases, 
for example with nitrogen or with argon. The proportion of the diluent can 
be up to 90% and preferably 30 to 50% of the halogen/inert gas mixture 
employed. 
The reaction according to the invention is carried out in the presence of 
light containing UV radiation, for example by irradiating the reaction 
mixture with a high-pressure or low-pressure mercury lamp. 
The process according to the invention is carried out at elevated 
temperature. An example of such a temperature which may be mentioned is a 
range from about 80.degree. C. up to the boiling point of the alkylbenzene 
of the formula (I). The temperature range from 30.degree. C. below the 
boiling point up to the boiling point of the alkylbenzene is preferred and 
the range from 10.degree. C. below the boiling point up to the boiling 
point is particularly preferred. 
The process according to the invention can be carried out under normal 
pressure or excess pressure, preferably under normal pressure. 
The halogenation in the process according to the invention is carried out 
to an extent such that the concentration of the halogenoalkylbenzene, 
newly formed by the monohalogenation, in the reaction mixture which is 
withdrawn from the reaction space is not more than about 33 mol %, 
relative to the number of mols of all of the substances contained in the 
reaction mixture. A concentration of 0.1 to 33 mol % and preferably 2-25 
mol % may be mentioned by way of example. 
The process according to the invention is carried out continuously. 
The reaction space is appropriately so designed that the liquid 
alkylbenzene and the gaseous halogen, which is optionally diluted with 
inert gas, are mixed well. For example, the reaction space can contain 
inserts, such as a frit, through the pores of which the halogen passes 
into the alkylbenzene which is flowing by, or a hollow cone with an 
annular nozzle, which functions in a similar manner. The reaction space 
can also, for example, be in the form of a Venturi tube. 
The reaction mixture can be worked up by customary measures, for example 
distillation, crystallisation or absorption, preferably by distillation. 
The end product obtainable from the working up can subsequently be further 
purified, for example by fractional distillation. During working up, the 
alkylbenzene employed in excess can be recovered and re-employed in the 
process according to the invention. 
The process according to the invention is generally carried out by 
introducing the alkylbenzene, which is in excess relative to the halogen, 
and the halogen into the reaction space and reacting them there in the 
temperature range according to the invention, under the action of light 
containing UV radiation. The reaction temperature, the level of the molar 
excess of the alkylbenzene, relative to the halogen, and the residence 
time of the reaction mixture in the reaction space are so chosen, 
depending on the starting materials, that the halogen is virtually 
completely converted in the reaction space. The reaction mixture is 
continuously removed from the reaction space and worked up by 
distillation. 
In the process according to the invention one can prepare compounds of the 
formula 
##STR3## 
in which R.sup.1 to R.sup.6 have the meaning indicated above and 
Hal represents chlorine or bromine, for example: benzyl chloride, benzyl 
bromide, 2-methylbenzyl chloride, 2-methylbenzyl bromide, 3-methylbenzyl 
chloride, 3-methylbenzyl bromide, 4-methylbenzyl chloride, 4-methylbenzyl 
bromide, 2-chloromethyl-benzyl chloride, 3-chloromethyl-benzyl chloride, 
4-chloromethyl-benzyl chloride, 3,4-dimethylbenzyl chloride, 
3-methyl-4-chloromethylbenzyl chloride, 2-chlorobenzyl chloride, 
3-chlorobenzyl chloride, 4-chlorobenzyl chloride, 2-chlorobenzyl bromide, 
3-chlorobenzyl bromide, 4-chlorobenzyl bromide, 2,4,5-trimethylbenzyl 
chloride, 2,4,5-trimethylbenzyl bromide, tetramethylbenzyl chloride, 
tetramethylbenzyl bromide, pentamethylbenzyl chloride, pentamethylbenzyl 
bromide, .alpha.-methylbenzyl chloride, .alpha.-methyl-benzyl bromide, 
dichlorobenzyl chloride, trichlorobenzyl chloride, tetrachlorobenzyl 
chloride, 2-chlorocarbonyl-benzyl chloride, 3-chlorocarbonyl-benzyl 
chloride, 4-chlorocarbonyl-benzyl chloride, 2-fluoro-benzyl chloride, 
3-fluorobenzyl chloride, 4-fluorobenzyl chloride, 2-fluorobenzyl bromide, 
3-fluorobenzyl bromide, 4-fluorobenzyl bromide, 2-cyanobenzyl chloride, 
3-cyanobenzyl chloride, 4-cyanobenzyl chloride, fluoro-chloro-benzyl 
chloride, fluoro-bromo-benzyl chloride, fluoro-bromo-benzyl bromide, 
isocyanatobenzyl chloride, chloroisocyanatobenzyl chloride, 
fluoro-isocyanatobenzyl chloride, fluoro-fluorocarbonyl-benzyl chloride, 
fluoro-cyano-benzyl chloride, fluoro-methyl-benzyl chloride, 
fluoro-methyl-benzyl bromide, chloro-methyl-benzyl chloride, 
chloro-cyano-benzyl chloride, 3-phenoxy-benzyl chloride, 
4-fluorophenoxy-benzyl chloride, chlorophenoxy-benzyl chloride, 
phenoxy-chloro-benzyl chloride, 2-bromobenzyl chloride, 3-bromobenzyl 
chloride, 4-bromobenzyl chloride, 2-bromobenzyl bromide, 3-bromobenzyl 
bromide, 4-bromobenzyl bromide, methoxy-chloro-benzyl chloride, 
3-phenoxy-4-fluoro-benzyl chloride, phenyl-benzyl chloride, 
2-trifluoromethylbenzyl chloride, 3-trifluoromethylbenzyl chloride, 
4-trifluoromethylbenzyl chloride, 3-trifluoromethyl-6-chlorobenzyl 
chloride, 4-trifluoromethyl-5-chloro-benzyl chloride, 
2-chloro-4-trifluoromethyl-benzyl chloride, 
2-chloro-3-trifluoromethyl-benzyl chloride, 
3-trifluoromethyl-4-chlorobenzyl chloride, 2,6-difluoro-benzyl chloride, 
2,4-difluoro-benzyl chloride, 2-chlorocarbonyloxy-benzyl chloride, 
4-trifluoromethylthio-benzyl chloride, 4-trifluoromethyloxy-benzyl 
chloride, 3-chloro-4-trifluoromethyloxy-benzyl chloride, 
4-heptafluoroisopropyl-benzyl chloride, 3,5-di(trifluoromethyl)-benzyl 
chloride, 4-isocyanato-benzyl chloride, 3-chloro-6-isocyanato-benzyl 
chloride, 4-chloro-6-isocyanato-benzyl chloride, 
5-chloro-6-isocyanato-benzyl chloride, 2-chloro-6-isocyanato-benzyl 
chloride, 2-fluoro-6-isocyanato-benzyl chloride, 
3-fluoro-6-isocyanato-benzyl chloride, 4-fluoro-6-isocyanato-benzyl 
chloride, 2,3-dichloro-6-isocyanato-benzyl chloride, 
3,5-dichloro-6-isocyanato-benzyl chloride, 
2,3,4-trichloro-6-isocyanato-benzyl chloride, 
2,3,4,5-tetrachloro-6-isocyanato-benzyl chloride, 
4-trifluoromethyl-6-isocyanato-benzyl chloride, o-nitro-benzyl chloride, 
m-nitrobenzyl chloride, p-nitrobenzyl chloride, 2-methyl-3-nitrobenzyl 
chloride, 2-methyl-4-nitrobenzyl chloride, 2-methyl-5-nitrobenzyl 
chloride, o-chlorosulphonylbenzyl chloride, m-chlorosulphonylbenzyl 
chloride, p-chlorosulphonylbenzyl chloride and benzal chloride. 
The substituted benzyl chlorides of the formula 
##STR4## 
in which 
R.sup.7 denotes trifluoromethoxy, trifluoromethylthio or 2-perfluoropropyl 
or also, if R.sup.8 represents chlorine, denotes trifluoromethyl and, 
furthermore, if R.sup.8 and 
R.sup.9 represent trifluoromethyl, denotes hydrogen, 
R.sup.8 represents hydrogen or also, if R.sup.7 represents trifluoromethyl 
or trifluoromethoxy, denotes chlorine and also, if R.sup.7 represents 
hydrogen and R.sup.9 represents trifluoromethyl, denotes trifluoromethyl, 
and 
R.sup.9 represents hydrogen and, if R.sup.7 represents hydrogen and R.sup.8 
represents trifluoromethyl, denotes trifluoromethyl, 
which can be prepared by the process according to the invention are new. 
The compounds, including the new compounds, which can be prepared according 
to the invention by monohalogenation of alkylbenzenes in the 
.alpha.-position can be used as intermediate products for the preparation 
of plant protection agents, for example, of herbicidal active compounds. 
Thus, according to DE-OS (German Published Specification) No. 1,668,243, 
for example the 3-trifluoromethyl benzylchloride can be reacted with 
sodium cyanide in the presence of dimethyl formamide at elevated 
temperature to yield the 3-trifluoromethyl benzylcyanide which is itself a 
valuable herbicide but which can be further hydrolized partially to yield 
the 3-trifluoromethylphenyl acetic acid amide by virtue of concentrated 
hydrochloric acid at 40.degree. C. or hydrolized completely by 10% by 
weight aqueous NaOH at the boiling temperature of the reaction mixture to 
yield the 3-trifluoromethylphenyl acetic acid. Both the said substituted 
acetic acid amide and the said free substituted acetic acid have a broad 
herbicidal effectiveness. According to GB No. 1,238,522 the 
3-trifluoromethyl benzylchloride can be first reacted with sodium or 
potassium cyanide to yield 3-trifluoromethyl benzyl cyanide which in turn 
is hydrolized completely to the corresponding substituted acetic acid 
chloride which in turn can be reacted with dimethylamine to yield 
3-trifluoromethylphenyl-N,N-dimethylacetamide which has herbicidal, 
nematocidal and fungicidal activity. Optionally substituted benzylhalides 
can be converted by known manners first to the corresponding 
benzylcyanides and, by hydrogenation, to the corresponding benzylamines 
which in turn can be reacted for example with N-tert-butyl-2-benzothiazole 
sulfenamide at 80.degree. to 90.degree. C., according to DE-OS (German 
Published Specification) No. 1,941,884, to yield 2-benzylaminethio 
benzothiazol which can serve as a vulcanization accelerator. Furthermore, 
the optionally substituted benzyl halides, for example 4-chlorobenzyl 
chloride can be reacted with potassium hydroxide with propane-1,3-diole to 
yield 3-(4-chloro-benzyloxy)-propane-1-ol which can be further reacted, 
according to DE-OS (German Published Specification) No. 2,365,762, with 
1-amino 2-phenoxy-4-hydroxy-anthraquinone in the presence of potassium 
carbonate at a temperature of 160.degree. C. to yield the corresponding 
anthraquinone dyestuff which dyes polyester and polyamide fibres in a 
brilliant pink colour. Furthermore the optionally substituted benzyl 
halides can be used in the Sommelet process to yield the corresponding 
benzaldehydes (Houben-Weyl, Handbuch der Organischen Chemie (Handbook of 
Organic Chemistry), Vol. VII/1, page 194, Georg Thieme Verlag Stuttgart 
1954), which are useful odorous substances or valuable intermediates for 
various purposes. 
Furthermore, the optionally subst. benzylhalides are useful for the 
preparation of selective benzylicether-herbicides according to German 
Offenlegungsschrift No. 2724 675. 
Thus, benzylchloride or benzylbromide can be reacted at elevated 
temperature with the alkololate from 3-hydroxytetrahydrofurane and sodium 
hydride, suspended in dioxane to yield the (3-tetrahydrofuryl)-benzylether 
which is an active herbicide against grassy weeds (German 
Offenlegungsschrift No. 2724675). 
The compounds prepared according to the invention by monohalogenation of 
alkylbenzenes in the .alpha.-position are obtained in high yields, in 
general of more than 90%, and usually of more than 94% of the theoretical 
yields, relative to the alkylbenzene converted, and in particularly high 
purity, so that they can be employed for many applications without further 
purification. 
As a result of the recycling, according to the invention of the uncoverted 
alkylbenzene (I), which is separated off from the reaction mixture after 
leaving the reaction space, high conversions, in general 80% or more of 
the alkylbenzene employed, can be achieved without interrupting the 
process. 
It is suprising that in the process according to the invention a uniformly 
high selectivity is maintained even with high conversions, since in the 
batchwise process according to the prior art (Houben-Weyl, loc. cit., page 
736), for example in the case of the chlorination of toluene, the process 
has to be discontinued at a 30% conversion in order to obtain a pure 
benzyl chloride. 
It is also surprising that strict exclusion of moisture, as is required 
according to the prior art (Houben-Weyl, loc. cit., page 736), is not 
necessary in the process according to the invention.

EXAMPLES 
(A) Reaction apparatus 
The reaction apparatus shown in the accompanying drawing is used in the 
examples which follow. The apparatus consists of a vaporizing vessel (g), 
which contains the starting compound. A column (f) which is filled with 
packing and into which an empty tube (e), which narrows towards the 
bottom, is inserted, is fitted on top of the vaporizing vessel (g). The 
reaction space (a), into which a device (b) is inserted, in which that 
portion located in the reaction space is designed as a recess (c), is 
located above the column (f). The halogen is fed from outside, through the 
inlet (d), into the device (b) to the recess (c) and, at the same time, 
the reaction space is irradiated with UV light. The thermometer (h) is 
also inserted in the reaction space (a) to check the reaction temperature. 
The condenser (i) is so arranged above the reaction space that the liquid 
component which condenses here can drip into the recess (c). 
(B) Reactions 
The reaction is illustrated by the following examples: 
EXAMPLE 1 
318 g of m-xylene are chlorinated in the apparatus described under (A). The 
heat supply to the vaporising vessel is so controlled that the amount of 
liquid xylene refluxing from the condenser (i) into the recess (c) is 
about 900 g/hour (about 8.5 mol/hour). After the reflux of m-xylene from 
the condenser has started, chlorine vapour is fed in an amount of 33 to 
33.5 g/hour (about 0.47 mol/hour) through the inlet (d) to the recess (c). 
The reaction mixture flows through the hole in the recess (c) into the 
tube (e). It contains about 5 mol % of 3-methylbenzyl chloride. The 
chlorination is discontinued when the conversion is 86%. According to 
analysis by gas chromatography, the product mixture in the vaporizing 
flask contains 341 g of 3-methyl-benzyl chloride, which corresponds to a 
yield of 94%, based on converted m-xylene. After fractional distillation 
pure 3-methylbenzyl chloride is obtained; boiling point.sub.13 =84.degree. 
C.; n.sub.D.sup.20 =1.5354; purity according to analysis by gas 
chromatography 98.14%. 
When the reaction is carried out continuously, chlorine and m-xylene are 
fed into the apparatus at the top while, at the same time, radiation with 
UV light is carried out continuously--and the chlorination product is 
continuously removed from the evaporator. The hydrochloric acid formed 
escapes at the top of the apparatus. 
The examples listed in the table were carried out analogously to the above 
example. 
__________________________________________________________________________ 
Degree of 
Product according to formula (I) 
Example 
Alkylbenzene conversion 
and yield 
__________________________________________________________________________ 
2 toluene 98.3% 94% 
##STR5## 
3 o-xylene 89% 93% 
##STR6## 
4 p-xylene 91% 94% 
##STR7## 
5 mesitylene 81% 90.5% 
##STR8## 
##STR9## 96% 98% 
##STR10## 
7 
##STR11## 77% 98.6% 
##STR12## 
8 
##STR13## 76.3% 97% 
##STR14## 
9 
##STR15## 80% 90% 
##STR16## 
10 
##STR17## 96% 99% 
##STR18## 
11 
##STR19## 86% 99% 
##STR20## 
12a 
##STR21## 34% 90.3% 
##STR22## 
12b 
##STR23## 87% 96.5% 
##STR24## 
__________________________________________________________________________ 
The following compounds are obtained with an equally good result by the 
process of 
Example 1: 
__________________________________________________________________________ 
13 
##STR25## Boiling point.sub.12 102.degree. C. 
n.sub.D.sup.20 1.4936 
14 
##STR26## Boiling point.sub.12 123.degree. C. 
n.sub.D.sup.20 1.5379 
15 
##STR27## Boiling point.sub.15 100.degree. C. 
n.sub.D.sup.20 1.5070 
16 
##STR28## Boiling point 185.degree. C. 
n.sub.D.sup.20 1.4549 
17 
##STR29## Boiling point.sub.15 100.degree. C. 
n.sub.D.sup.20 1.4788 
18 
##STR30## Boiling point.sub.50 109.degree. C. 
n.sub.D.sup.20 1.4251 
19 
##STR31## Boiling point.sub.16 68.degree. C. 
Melting point about 28.degree. C. 
20 
##STR32## Boiling point.sub.10 117.degree. C. 
Melting point 34.degree. C. 
__________________________________________________________________________ 
EXAMPLES 21-24 (Comparison Examples) 
For the alkylbenzenes listed in the table, a chlorination was carried out 
according to Example 1 with conversions of above 80% and the by-products 
obtained were determined. For comparison, a bottom phase chlorination 
according to the instructions in Houben-Weyl, Methoden der Organischen 
Chemie (Methods of Organic Chemistry), volume V/3, page 736, Verlag Georg 
Thieme, Stuttgart, 1962 was carried out and the degree of conversion at 
which the same amount of by-products is obtained was determined. 
______________________________________ 
Degree of conversion (%) 
according 
to the By-products 
No. Alkylbenzene 
invention prior art 
(% by weight) 
______________________________________ 
21 mesitylene 81 40 7.6 
22 o-xylene 88.5 43 5 
23 m-xylene 86 40 5 
24 p-xylene 85 43 5 
______________________________________