DE1068250B - Process for the preparation of methyl isorhiocyanate - Google Patents

Description

The invention relates to the production of methyl mustard oil. The isothiocyanates have been used in pest control Found application, the methyl isothiocyanate in the fight against soil, nematodes has proven to be particularly suitable. S.

A number of methods are already known, according to which aliphatic isothiocyanates can be produced.

For example, isothiocyanates can be produced by rearranging thiocyanic acid esters of the formula RSCN. Also at the treatment of N-monosubstituted alkyldithiocarbamates with heavy metal salts results in mustard oils. Another way of representing isothiocyanate is the action of thiophosgene on amines. Further aromatic isothiocyanates can also be obtained from thiocarbanilides through the action of concentrated hydrochloric acid be won. Another way leads over the isonitrile, from which by addition of sulfur likewise Mustard oils can be produced. In addition, ditliiocarbamates can be treated with oxidizing agents in ao Mustard oils are transferred, whereby the presence of heavy metal salts is appropriate. Mustard oils can also be made from dithiocarbamates and cyanogen chloride will. Furthermore, thioureas can be reacted with carbon disulfide at an elevated temperature. This »5 However, the method requires the application of pressure, which is a significant complication in the technical Implementation means. It is also known that organic isothiocyanates can be obtained by reacting N-monosubstituted compounds Dithiocarbamic acids or their salts in the presence of a solvent with hypochlorites or can produce chlorites. However, these processes only deliver good yields with the higher mustard oils, in contrast, in various attempts to prepare methyl isothiocyanate only yields of about 40 to 50% (with lower demands on the Degree of purity). In addition, these processes require extremely large amounts of solvent, what is not the case with the method according to the invention described below.

Another process for the preparation of isothiocyanates consists in reacting dithiocarbamates in an aqueous medium with chloroformic acid esters. The products that can be manufactured using this method
of methyl isothiocyanate

Applicant:

Schering Aktiengesellschaft,
Berlin N 65, Müllerstr. 170-172

Dr. Horst Werres, Berlin-Charlottenburg,
has been named as the inventor

Procedures received, however, are very impure. In the literature, yields of 70 to 76 ° / ₀ are given for the preparation of methyl isotiocyanate, but these yields could not be achieved in general. The product obtained by this method is also partly liquid, partly solid and has a carbon content that is too high by 10 ° / _0th

It is also known that aromatic isothiocyanates can be obtained by reacting the corresponding dithiocarbamic acids Ammonium salts can be obtained in an anhydrous medium with phosgene. As a solvent here primarily anhydrous toluene is used.

It has now been found that methyl mustard oil can also be used by reacting N-methyldithiocarbamates with Can produce phosgene. It was not easy to foresee that this reaction would take place in the aromatic Isothiocyanates succeed, can also be carried out with the aliphatic isothiocyanates. Furthermore this is Surprisingly, the reaction can also be carried out in an aqueous medium. The reaction even works in water better than in organic solvents. Carrying out this reaction in aqueous solution was special therefore not to be foreseen, because phosgene hydrolyzes in water. So it must be the reaction according to the invention of phosgene also in an aqueous medium with priority in terms of the reaction scheme

CH ₃ -NH-CS-alkali + COCl ₂ > CH ₃ -N = C = S + alkaliCl + HCl + COS

where alkali e.g. = Na can run.

The advantage of the process according to the invention is that very pure products are obtained immediately. Further working in water is more economical than working in organic solvents. Another advantage is that all soluble carbamates can be used, such as the sodium salts of the corresponding ones Dithiocarbamic acids. It is particularly cheap

'That the solubility of the alkali salts of the dithiocarbamic acids is particularly good; there is also the advantage of being able to use

909 547'-i? 3

Claims (2)

3 4 to be able to work in the hosnogenic phase. Diireh the export meter and inlet pipe for phosgene. The phosgene capacity of this reaction in an aqueous medium is saved, and the sici ₍ i the moisture exclusion and the drying of the phosgene also via a flow meter and via the starting products that are used in the production of aromatic safety bottles through the inlet pipe into the isothiocyanates through conversion of the corresponding 5 flasks. Behind the reaction flask, dithiocarbamic acid ammonium salts are placed in an anhydrous one an absorption vessel for the COS formed, e.g. medium with phosgene is necessary. Furthermore, there are a bottle with alcoholic ammonia. In the above inventive reaction easily accessible exit The solutions obtained are available in materials at an internal temperature of 50 ° C. Compared to the approximately 3 hours already passed, 195 g of phosgene are introduced recstcr has also separated the prefix. The separation can be carried out either directly or by partial etherification in place of the chloramic acid parent. It is useful to be able to use phosgene. The chloroformic acid ester should be added moderately, at first about 200 ecm of water, otherwise the sodium chloride separated would have to be prepared from phosgene and alcohol to dissolve it. Furthermore, the COS obtained during the reaction is a valuable starting product, dried with sodium sulfate, and distilled at normal pressure over an approximately 10 cm long column, e.g. for the production of other pest control products, which is filled with Raschig rings. The boiling point of the main run is between 115 and 118 ° C. An example of a small tail is still collected, with the. _T,. ".. ,,,,.,. ,., - », ao boiling temperature drops to about 104 ° C. The template is a) Production of N-methyldrthiocarbamidsaurem Na- _{with Εί} ^ _{ΚΡΓ fekühh To dn} crystallize out in ^Just to avoid a cooler, this will only work with a weak one The apparatus consists of a triple-tubed air stream or not cooled at all. The yield at 1-1 round bottom flask with reflux condenser, thermometer, pure mustard oil is 65.3 g = 51.8 ° / ₀ if the solution KPG stirrer and dropping funnel. 110 ecm = 137g of the N-methyldithiocarbamic acid sodium used Felt carbon and a cold solution of 72 g of sodium - about 41% ig (percent by weight) is what by analysis hydroxyd in 160 g of water is added to the flask. The melting point of the obtained and then in about 30 minutes 184 ecm (= 55.8 g of methyl product is included without further cleaning measures amine) of a commercially available 33 ° / _o aqueous solution of methylamine 36.0 to 37.0 ° C. added dropwise. The internal temperature is thereby reduced by 30 The yields in further batches were between Temporary cooling kept below 25 ° C. After that 51 and 56%.
is stirred until it becomes clear, reddish
Solution has formed. There is also a time from about 1 to 2 hours required. The total volume of the patent claim: The remaining solution is 440 ecm. 35 For the production of the N-methyldithiocarbamine process for the production of methyl isothiocyanate, acidic sodium is in the context of the present characterized in that N-methyldithio- Invention not claiming patent protection. carbamate is reacted with phosgene in aqueous solution. b) Production of methyl isothiocyanate The apparatus consists of a triple tubulated ^Contemplated publications: 1 l round bottom flask with reflux condenser, stirrer, Thermo- German patent no. 960276. ® 909 «47/433 10.59