DE569690C - Process for the preparation of chlorinated cresols - Google Patents

Description

Process for the preparation of chlorinated cresols .kls process for a technical production of polychlorocresols, such as. B. from trichlorocresol comes the chlorination of the Liresole itself is out of the question, since the chlorination of the o- or p-cresol after L, the dichloro stage simultaneously oxidizes to form quinone-like Compounds occur which are a cumbersome and loss-making cleaning process make it necessary. The few trichlorocresols known so far in the literature are awkward by chlorinating the corresponding chlorotoluidines and Reduction of the hexachloroketones obtained in this way, as from the work Zinkes (Annalen 417 [i 9 i 81, p. 197 f.) Emerges. Only with the m-cresol succeeds in producing a uniform trichlorocresol through direct chlorination, since here the o- and p-positions with respect to the hydroxyl group are free; it stands however, a utilization of a trichlorocresol produced in this way m-Kresols opposed the high price, which, as is well known, is only available on cumbersome. way can be obtained from the raw cresols.

It has been found that the monosubstituted or multiply chlorine-substituted Cresol instead of liresoles can be obtained technically more advantageously in a roundabout way, by first chlorinating toluene or low-substituted chlorotoluenes the easily accessible chlorotoluenes of the desired chlorination stage and then on these alcoholic or alcoholic-aqueous alkali hydroxides at higher levels Allowing temperatures and the associated pressures to act. Here is a similar Way, as is known for the chlorobenzenes, -one chlorine atom against the hydroxyl group exchanged. The basis of the present invention is the observation that the Effect of the alkali hydroxides on the various stages of chlorination of the Temperature is dependent and that the reaction temperature can be adjusted can that from mixtures of (tt - (- i) -chlorotoluenes with (rz) -chlorotoluenes only the former are converted into the corresponding (tt) -chlorocresols, while the (n) -Chlortoluenes remain unchanged. (Tt) means the one present in each case Number of chlorine atoms. Mixtures of this type in which the fit -'- i) -Chlortoluenes compared the (n) -chlorotoluenes by far predominate, are very easy to chlorinate obtain.

So you can z. B. for the production of a mixture of trichlorocres isomers of a crude tetrachlorotoluene which still contains trichlorotoluene, so that neither "the exact achievement of the stage of tetrachlorination and also a purification of the crude product by the cumbersome fractional distillation is necessary in the production of the crude tetrachloro toluene. Since, according to the experiments, a much higher temperature is required for the reaction of the trichlorotoluene with alcoholic alkali than for the conversion of the tetrachlorotoluene into trichlorocresol, the amount of alkali calculated for the exchange of a chlorine atom from the tetrachloro-toluene can be obtained by using the formula and from temperatures of about 16o to 70o bring about the reaction without the trichlorotoluene being tapped. The latter can easily be removed from the trichloro resole solution and either reused in a further batch in the production of crude tetrachlorotoluene or after the g easy process, but at elevated temperature, convert it into dichlorocresol. Examples i. 500 kg of crude tetrachlorotoluene with a content of about 66% pure tetrachlorotoluene, the remainder being trichlorotoluene, are heated to 170 ° for 15 hours with 8oo 1: g of methanol and .10o kg of 35% sodium hydroxide solution. When the methanol is distilled off , the unchanged trichlorotoluene is precipitated. The lye is separated off and acidified, and the trichloro-cresol mixture can be drawn off as an oil that solidifies at about 65 °. It can be obtained in pure form as a colorless mass by distillation in vacuo. The yield of crude tetrachlorotoluene is 250 kg and corresponds almost to the theoretical amount to be expected from the crude tetrachlorotoluene used.

2.5oo 1g crude pentachlorotoluene with a content of about 7o% pure pentachlorotoluene, The remainder of the tetrachlorotoluene are in a pressure autoclave with 8oo kg of methanol and 16o kg Iialiumhy droxvd for 10 hours heated to 130 to 140 '. After distilling off the methanol and dilution with water, the aqueous alkali is separated from the unreacted product enntund an acidified. About 2.1o kg of almost pure 2, 3, 5, 6-tetrachloro-cresol are obtained.

As the technical, by chlorination of toluene or substituted Tetrachlorotoluene obtained from chlorotoluenes from mixtures of different isomers exists, there is no uniform product even if it is converted into trichlorocresol, but a mixture of isomers. However, this represents nianclien uses the "fricb @ orkrc @ -sole not itn ways.

It works in an analogous way. Cresol tetrachloride from tetrachlorotoluene containing pentachlorotoluene, in which one is exposed to the alcoholic Alkali hydroxide solution maintains a temperature of about 130 to 14o '; here remains the tetrachlorotoluene changed.

For the production of dichlorocresol from a containing dichlorotoluene Trichlorotoluene reacts with the alkali hydroxide solution at about i8o to igo ° perform to. to leave the dichlorotoluene unchanged.

Finally, in an analogous manner, from a mono- and dichlorotoluene mixture 3Ionachlorocresol can be obtained when the reaction temperature drops to about zoo up 2 is held, the monochlorotoluene not participating in the implementation.

If instead of the isomer mixtures of an (it-A-i) -chlorotoluene a single Isomer of (it + i) -chlorotoluene, which still contains (n) -chlorotoluenes, according to the Invention treated, so can in compliance with the appropriate above specified Temperatures the corresponding individual (a) -chlorocresols can be obtained.

Claims (1)

PATENTANSt'IZIIC: li: Process for the preparation of chlorinated oils, characterized in that. one mixtures of (jt-j - i) -chlorotoluenes with (it) -chlorotoluenes [n = number of chlorine atoms], in which the former strongly predominate, with one the (lt i) -Chlortoluenegelialt calculated amount of alcoholic or aqueous-alcoholic Alkali hydroxide reacts under pressure at temperatures at which only the (it T i ) -Chlortoluene reacts and after the reaction the resulting (tt) -Chlorkresollösung separated from the unchanged (n) -chlorotoluene.