Liquid-phase oxidative chlorination of tert-butylbenzene

Petrol. Chem. U.S.S.R. Vol. 24, No. 3, pp. 132-135, 1984 Printed in Poland

0031-64581'84 $10.00 ~ .i)0 © 1986 Pergamon Press l a d

LIQUID-PHASE OXIDATIVE CHLORINATION OF tert-BUTYLBENZENE* F. F. MUGANLINSKII, F'. M. SHAKHVERDIYEVA, B. SH. SHAKHPELENGOVAand YE. A. GAZARYAN M. Azizbekov Institute of Petroleum and Chemistry, Azerbaijan (Received24 April 1984)

SEVERAL publications have appeared in the literature during recent years dealing with liquid-phase oxidative chlorination of hydrocarbons. The interest in this reaction is due to its potential for higll selectivity, compared with processes of vapourphase oxidative chlorination. Previous papers [1, 2] examined liquid-phase oxidative chlorination of benzene and toluene, producing monoclllorobenzene and monochlorotoluene with high selectivity. Study of the possible introduction of an ~-chlorine atom into the nucleus of higher alkylbenzenes by liquid-phase oxidative chlorination is of undoubted interest. There is no information in the literature concerning this possibility due apparently to the difficulty experienced in attempting the introduction of a chlorine atom into the nucleus of aromatic hydrocarbon deactivated with a bulky alkyl group. This paper examines the liquid-phase oxidative chlorinatiort of tert-butylbenzene using hydrochloric acid mixed with hydrogen peroxide as chlorinating agent. EXPERIMENTAL

Oxidative chlorination was carried out in a three-neck flask provided with a stirrer, reflux condenser, electrolyzer-measuring device for the supply of hydrogen peroxide. Temperature was maintained with an accuracy of +0-5°C. A given amount of hydrochloric acid and tert-butylbenzene was placed into the reaction flask. When a given temperature was reached with continuous stirring a calculated amount of hydrogen peroxide was introduced into the flask via an electrolyzer-measuring device. After addition of hydrogen peroxide, the mixture was maintained under experimental conditions while stirring constantly for a given lertgth of time to complete oxidative chlorination. After the reaction, the hydrocarbon layer was separated from the water layer, neutralized with a weak soda solution, dried over calcium chloride and analysed. The reaction products (hydrocarbon layer) were monitored by gas-liquid chromatography (LKhM-SMD chromatograph). Distillation of the hydrocarbon layer yielded a tert-butylmonochlorobenzene fraction b.p. 212-213/0.1 MPa, the isomeric composition of which was interpreted * Neftekhimiya 24, No. 4, 537-540, 1984, 132

Liquid.phase oxidative chlorination of tert-butylbenzene

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chromatographically (Fig. 1). [4 ram×3 m column filled with Chromosorb G cartying 5~o vet. Apiezon L; gas flow (helium) 35 ml/min; colnmn temperature 20&C]. In the IR spectrum of tert-butyichlorobenzenes absorption bands were observed at 835-810 cm -1, which are typical of p-tert-butylchlorobenzene and bands at 750, 735 cm -x, typical of o-tert-butylchlorobenzene. The ratio of p- and o-tert-butylchlorobenzenes is 9 : 1 . p-tert-butylmonochlorobenzene was separated from the isomeric mixture by freezing. Physico-chemical constants of the p-tert-butylmonochlorobenzene (n2° 1.5108, d 2° 1.0056; t,o, 35°C) show satisfactory agreement with results in the literature [3]. 3

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FIo. 1. Chromatographic curve of tert-butylmonochlorobenzenes: I-tert-butylbenzene (1 : 1); 2-o-tert-butylcldorobenzene (1 : 10), 3-p-tert-butylchlorobenzene (1 : 30). The effect of hydrogen chloride consumption, reagent ratio, temperaXure and process time on the distribution of reaction products and yield of the end-produat w e r e examined. RESULTS

The effect of hydrogen chloride consumption on the distribution of reaction products and the yield of tert-butylchlorobenzene was studied using a stoichiometric ratio of tert-butylbenzene to hydrogen peroxide, process temperature being 20°C. The results shown in Fig. 2a, indicate that increasing hydrogen chloride consumption from 1 to 6 mole, increases the content of tert-butylchlorobenzene in the reaction

134

F.F.

MUGANLINSKII e t a l .

mass from 13 to 52 wt. ~ but any further increase in the amount of hydrogen chloride reduces the content of tert-butylchlorobenzene and increases the content of tert-butyldichlorobenzene from 0 to 12 wt. ~o, as a result of further chlorination of the tert-butylchlorobenzene formed and shows the step-by-step formation of benzene dichloroderivatives. w~.% 100

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Fie. 2. Distribution of reaction products according to HCI consumption (a), temperature (b), experimental time (e) and the concentration of hydrolgcn peroxide (d). a, c, d - t 200C; a, b-experimzntal time 5 hr, d - 7 hr; b, c, d-tert-butylbenzcne : HC1 : H 2 0 = I : 6:1, mole/mole; 1 transformation of tert-butylbenzene; 2 - tert-butylchlorobenzenes; 3 - tert-butyla~ohlorobenzenes. Figure 2b s~mmarizes the effect of temperature on the distribution of reaction products in the hydroxyolflorination of tert-butylbenzene. It follows from the Figure that inoreasing the temperaXure from 0 to 80°C accelerates hydroxy-chlorination, as a result of which the content of tert-butylchlorobenzene in the reaction mass increases from 42 to 64 Wt. ~o. The content of tert-butyldidflofobenzeaes increases from 0 to 10~o, respectively.

Liquid-phase oxidative chlorination of tert-butylbenzene

135

The duration of hydroxychlorination has an effect on process selectivity. At 20°C the content of tert-butylchlorobenzene in the reaction mixture reaches 52 ~o after 5 hr whilst the content of tert-butyldichlorobenzene is 3.5 ~o (Fig. 2c). Increasing the duration of the reaction to 7 hr slightly increases the content of tert-butylchlorobenzene (to 54 ~), while the amount of tert-butyldichlorobenzenes in the reaction mixture increases to 10 ~o- Further increase in reaction time (8 hr) reduces the yield of tert-butylchl orobenzene. The effect of hydrogen peroxide concentration on the distribution of products of hydroxy-chlorination of tert-butylbenzene was examined at 20°C, a molar ratio of TBB : HC1 : H 2 0 2 of 1 : 6 : 1, (reaction time 5 hr) is shown in Fig. 2d. The Figure shows that there is no point in increasing the concentration of hydrogen peroxide above 30 ~o since it only slightly increases the content of tert-butylchlorobenzene in the reaction mass (not more than 3 ~o) and at the same time causes a deterioration in selectivity. Tert-Butylbenzene has a considerable effect on the hydroxy-chtorination of tert-butylbenzene. Dilution of the reaction mass with tert-butylbenzene from 1 to 6 mole increases the yield of tert-butylchlorobenzene from 49.02 to 57 ~o of theory, on a hydrogen peroxide basis. The yield of tert-butyldichlorobenzene decreases from 3.5 to 0 ~o. Further dilution of the reaction mass with tert-butylbenzene reduces the yield of tert-butylchlorobenzene. SUMMARY

Liquid-phase oxidative chlorination of tert-butylbenzene was studied in hydrochloric acid in the presence of hydrogen peroxide as oxygen source. It was shown that at 20°C, with a molar ratio of tert-butylbenzene : HC1 : H202 of 6 : 6 : 1 and a reaction time of 5 hr, tert-bntylchlorobenzene yield on hydrogen peroxide is 75 % with 100% selectivity. REFERENCES

1. F.F. MUGANLINSKII, M. M. GUSEINOV, Ye. A. GAZARYAN, F. M. SHAKHVERDIYEVA and N. E. DZHABAROVA, A.c. 514802; 13.12.1975. Byull. izobr., No. 19, 52, 1976 2. F. F. MUGANLINSKII, G. B. SERGEYEV, Ye. A. GAZARYAN, M. M. GUSEINOV, F. M. SHAKHVERDIYEVA, V. V. SMIRNOV and V. V. KAS'YANOV, A.¢. 759500; 23.05.1978, Byull. izobr., No. 32, 99, 1980 3. M. S. SALAKHOV, M. M. GUSEINOV, Ch. A. CHALABIYEV and D. K. ABDULAYEV, Neftekhimiya, 14, No. 3, 1974 4. M. LERER, C. FABRE and G. HUGEL, Bull. Soc. chimie, France, 8-9, 1238-1243, 1956