JPH0128113B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing monochlorotoluene. More specifically, when toluene is electrolytically chlorinated using an electrolyte salt containing chlorine, a method for producing only monochlorotoluene without producing dichlorotoluene by a combination of a limited solvent and an electrolyte salt containing chlorine is described. It depends. Monochlorotoluene is used in large quantities as an important raw material in various organic chemical industries such as dyes, pigments, and agricultural chemicals, or as an organic solvent. Currently, these monochlorotoluenes are produced using toluene as a raw material.
The mainstream is the so-called chemical production method, in which synthesis is performed using chlorine in the presence of a catalyst or an organic solvent. For example, a method using iron chloride as a catalyst (JACS Vol. 76, p. 5491, 1954), a method using iron ores such as pyrite and magnetite (Japanese Patent Application Laid-Open No. 1983-64231),
Method using selenium and iron powder (Special Publication No. 50-34009),
Method using iron powder and sulfur compounds (French patent no.
1491143-4) are well known, but all of these production methods use harmful chlorine gas and the reactions are relatively radical, so at the same time side reactions that produce tar-like unknown components proceed, It is not possible to overcome the drawback that not only monochlorotoluene, which is the target product, is produced, but also a large amount of dichlorotoluene is produced. On the other hand, electrochemical methods, which have recently begun to attract attention as a new method for organic synthesis, generally speaking are methods that are less likely to cause side reactions and have excellent selectivity, but their current efficiency is not very high. Therefore, in order to improve the yield, electricity is often applied in an amount greater than the theoretical amount of electricity. Even under such circumstances, the results of suppressing the production of dichlorotoluene, which is the drawback mentioned above, by the method known as the electrolytic chlorination method of toluene have not yet been known. For example, if twice the theoretical amount of electricity is applied using lithium chloride as an electrolyte salt containing chlorine and platinum as the anode metal in an acetonitrile solvent, 10%
The dichloro form of is living body (Electro.Chim.Acta.Volume 24)
(p. 1039), and when lithium perchlorate is further added, 50% of dichlorotoluene is produced by applying 1.5 times the theoretical amount of electricity (ibid.). Under these circumstances, the present inventors completed the present invention as a result of intensive research into electrolytic chlorination conditions that can selectively produce only monochlorotoluene without producing dichlorotoluene. That is, the present invention uses toluene in methyl alcohol that may contain 5% or less water, using one or more of lithium chloride, ammonium chloride, and sodium chloride as an electrolyte salt containing chlorine.
This is a method for producing monochlorotoluene that does not produce dichlorides, which is characterized by electrolytic chlorination. When using something other than methyl alcohol as the electrolytic solvent, the yield of monochlorotoluene was improved by applying more than the theoretical amount of electricity, but at the same time dichlorotoluene and/or unknown components were produced, and it was difficult to suppress these side reactions. This was not possible by changing external conditions. The electrode material used in the present invention may be any commonly used material, but particularly preferred anode materials include platinum, graphite,
There is DSA (a titanium substrate whose surface is coated with ruthenium oxide). Although the electrolysis temperature is carried out at room temperature, the effects of the present invention will not change even if the temperature is higher. However, preferably the temperature changes during the reaction should be controlled within a small range. Also, the anode voltage is 1.0 to 2.5 volts, preferably 1.3 to 2.1 volts, relative to the saturated electrode.
Good voltage range in volts. If the influence of water mixed in methyl alcohol as a solvent is 5% (by volume) or less, the effects of the present invention will not be significantly reduced. Further, the amount of current applied is in the range of 2 to 4 faradays (F) per 1 mole of toluene. Furthermore, as an effect of implementing the present invention, even by increasing the electrolytic voltage in an actual industrial method, the monochlorination reaction rate can be accelerated without producing a dichloro compound. In order to explain the effects of the present invention more specifically and in detail, examples will be given below. Examples 1 to 9 Using an H-type electrolytic cell with a glass filter diaphragm in the center, a solution of an electrolyte salt containing 0.025 mol of chlorine dissolved in 30 ml of a solvent (3% aqueous methyl alcohol) was placed in each chamber, and the anode An additional 0.005 mol of toluene was added to the chamber, and electrolytic chlorination was carried out in a constant temperature bath with the potential of the anode constant relative to the saturated Amane electrode. The results are shown in the table below.

[Table] Examples 10 to 12 According to Example 1, using 1%, 3%, and 5% hydrous methyl alcohol as a solvent, lithium chloride as an electrolyte salt containing chlorine, platinum as an anode material, and an electrolysis temperature of 30°C. carried out. The results are shown in the table below.

[Table] Example 13 Using an H-type electrolytic cell with an anion exchange membrane in the center, 0.0125 mol of sodium chloride and 30 ml of water were placed on the cathode side.
Add the solution dissolved in lithium chloride to the anode side.
A solution of 0.0125 mol of toluene and 0.005 mol of toluene dissolved in 30 ml of methyl alcohol was placed in a constant temperature bath at 30°C, and the potential of the anode was set to 1.3 volts with respect to the saturated oxidized electrode, and an amount of electricity of 2.3 fura days was passed through. Electrolytic chlorination was performed. After the electrolysis experiment, 49.6% of the toluene initially dissolved in the anolyte had become monochlorotoluene, and 45.9% of toluene remained unreacted. It was confirmed by gas chromatography that dichlorotoluene was not produced.

Claims (1)

[Claims] 1 Toluene in methyl alcohol that may contain 5% (by volume) or less water, using one or more of lithium chloride, ammonium chloride, and sodium chloride as an electrolyte salt containing chlorine,
A method for producing monochlorotoluene that does not produce dichlorides, characterized by carrying out electrolytic chlorination under the conditions of an anode potential of 1.0 to 2.5 volts (vs. saturated Amane electrode) and a current flow of 2 to 4 Faradays/mol of toluene.