Process for producing chlorinated tertiary carbon-containing...

Details Process for producing chlorinated tertiary carbon-containing... Process for producing chlorinated tertiary carbon-containing...

1999-04-27

2001-02-13

Siegel, Alan (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Halogen containing

C570S261000

Reexamination Certificate

active

06187977

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for producing a chlorinated hydrocarbon compound. More particularly, it relates to a process for selectively chlorinating a tertiary carbon atom(s) of a hydrocarbon compound by using a hypochlorous acid compound.
The thus-synthesized compounds having a chlorinated tertiary carbon atom are useful as a reagent in various syntheses which utilize the reactivity of a chlorine substituent. For example, an aromatic group-substituted chlorinated hydrocarbon such as 1,4-bis(1-chloro-1-methylethyl)benzene (1,4-dicumyl chloride, p-Cl(CH
3
)
2
CC
6
H
4
C(CH
3
)
2
Cl) is known to be useful as a cationic polymerization initiator in the production of terminally functional polyisobutylene and the like [U.S. Pat. Nos. 4,276,394 and 5,527,870 (Maeda et al., 1994)].
PRIOR ART
As a process for producing such a initiator, the following processes are known which use 1,4-diisopropylbenzene as a starting material.
One comprises synthesizing 1,4-diisopropenylbenzene (CH
2
═(CH
3
)CC
6
H
4
C(CH
3
)═CH
2
) by dehydrogenation (U.S. Pat. No. 3,429,941) and subjecting the same to hydrogen chloride addition reaction (O. Nuyken et al., Makromol. Chem., 186, 173 (1985)). Another known process comprises synthesizing 1,4-bis(1-hydroxy-1-methylethyl)benzene (1,4-HO(CH
3
)
2
CC
6
H
4
C(CH
3
)
2
OH) by oxidation with air (e.g. Japanese Kokai Publication Sho-60-174737) and reacting the same with hydrogen chloride (V. S. C. Chang et al., Polymer Bulletin, 4, 513 (1981)).
While at least two reaction procedures are required in the syntheses mentioned above, a one-step process reported for synthesizing the desired 1,4-dicumyl chloride comprises reacting 1,4-diisopropylbenzene (1,4-H(CH
3
)
2
CC
6
H
4
C(CH
3
)
2
H) with chlorine gas under sunlight irradiation (M. S. Kharashch et al., J. Am. Chem. Soc., 61, 2142 (1939)). In the reaction under sunlight irradiation, however, to control the selectivity concerning the chlorine substitution sites is a problem.
On the other hand, a process reported for obtaining 1,4-dicumyl chloride by chlorinating 1,4-diisopropylbenzene at the benzyl sites thereof comprises reacting with sodium hypochlorite in the presence of a phase transfer catalyst (Bu
4
N(HSO
4
)) (H. E. Fonouni et al., J. Am. Chem. Soc., 1983, 105, 7672). However, this process uses an expensive phase transfer catalyst, hence cannot be said to be an industrially advantageous process. A process which comprises effecting chlorination with hypochlorous acid without using any phase transfer catalyst has also been reported (F. Minisci et al., Chim. Ind., 70, 52 (1988); Japanese Kokai Publication Hei-09-143106).
The process for obtaining 1,4-dicumyl chloride by chlorinating a tertiary carbon of 1,4-diisopropylbenzene by use of hypochlorous acid involves only one reaction step and is effective and higher in selectivity as compared with photochlorination. However, hypochlorous acid is a very unstable substance and it is difficult to prepare and store hypochlorous acid always at a constant concentration. Therefore, even when constant charge amounts are set for the raw materials, it is difficult to attain a stable reaction yield, selectivity and product quality due to fluctuation of the equivalent relationship.
Furthermore, when hypochlorous acid is employed, it is necessary to neutralize the hypochlorous acid with an alkali for terminating the reaction. On the other hand, the product 1,4-dicumyl chloride is very unstable against water in an alkaline medium and, when it is in contact with water, the hydrolysis reaction will proceeds, leading to quality deterioration.
1,4-Dicumyl chloride is also deteriorated when in contact with a metal. Means conceivable for overcoming this disadvantage is to employ glass lining or Teflon lining in most of the process equipment. With such material, however, electrostatic elimination by earthing is essentially difficult and therefore, when the liquid contents are electrically charged, there arises a risk of pinhole formation due to electrostatic sparking. Therefore, in the lined equipment, it is important to take adequate measures against static electricity. A known measure against static electricity comprises adding an antistatic agent. In some instances, however, this method is unfavorable since the antistatic agent, if remaining in the product, may affect the quality thereof.
While the production of 1,4-dicumyl chloride by using hypochlorous acid is disclosed in Japanese Kokai Publication Hei-09-143106 as well, the technology of Japanese Kokai Publication Hei-09-143106 cannot be said to be a production process suited for industrial application, since the problem mentioned above has not been solved.
The problem to be solved in conducting the chlorination reaction by using a hypochlorous acid compound effectively is how to introduce chlorine selectively into desired sites alone. Hypochlorous acid, which is required for said reaction, is a very unstable substance and it is difficult to prepare and store hypochlorous acid always at a constant concentration. In the conventional procedure for preparing hypochlorous acid by admixing hydrogen chloride, chlorine gas is produced, hence it cannot be said to be an industrially advantageous procedure from the safety viewpoint and for the reason that the utilization percentage of the raw material sodium hypochlorite is reduced. The thus-prepared hypochlorous acid tends to decrease in its concentration until it is used in the chlorination reaction. Therefore, it becomes impossible to charge hypochlorous acid in a constant amount relative to the reactant to be chlorinated and, as a result, it is difficult to obtain a stable reaction yield, selectivity, and a product quality.
Another essential point in improving the reaction selectivity and yield and realizing quality stabilization is how to terminate the chlorination reaction. A known method of deactivating hypochlorous acid to terminate the reaction comprises making the medium alkaline and then adding sodium sulfite. However, investigations made by the present inventors revealed that the obtained chlorination product is subject to hydrolysis when in contact with water in an alkaline medium. Therefore, said method can hardly be employed as it is.
Furthermore, there is a major problem from the industrial application viewpoint, namely measures against static electricity in cases where lined equipment is used. In the process according to the present invention, the chlorination product obtained, if in contact with a metal, will be deteriorated. Since a protic acid is used, the equipment, if made of an ordinary metal, will be corroded. Corrosion-resistant metals are indeed available, such as tantalum, platinum and gold, but these are special materials and are very expensive, hence the use thereof is not practical. For these reasons, it is thought that lined equipment should be used in industrial application of the process. In such equipment, however, there is a risk of pinhole formation due to sparking if measures against static electricity are not taken. Sparking becomes particularly significant when the content liquid tends to be easily charged electrostatically. The content liquid occurring as a slurry as a result of crystallization is known to be especially readily chargeable and therefore measures against static electricity are very important in the step of crystallization. As a measure against static electricity, there is a method comprising adding an antistatic agent. However, the antistatic agent, if remaining in the product, may unfavorably affect the quality of the product.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the problems encountered in chlorinating the tertiary carbon atom or atoms of a hydrocarbon compound by using hypochlorous acid, namely the reaction selectivity and operability problems, the problems concerning the method of terminating the reaction, and the problems concerning the measures against static electricity for enabling industrial application of the process in questio

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