JPS62263988A - Electrochemical production of cyclohexanol or its ester - Google Patents

Abstract

PURPOSE:To electrochemically produce cyclohexanol or an ester thereof at a high conversion rate by adding a supporting electrolyte to a soln. of cyclohexane in a fatty acid and electrolyzing the resulting electrolytic soln. CONSTITUTION:Cyclohexane is dissolved in a fatty acid such as acetic acid and a supporting electrolyte consisting essentially of sulfuric acid and water is added. The resulting electrolytic soln. is electrolyzed at about 1.5-2.6V anode potential basing on the potential of a satd. calomel electrode. By the electrolysis, the cyclohexane is electrochemically oxidized on the surface of the anode to produce cyclohexanol. This cyclohexanol bonds nonelectrochemically to the fatty acid as a solvent, producing cyclohexyl ester.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for electrochemically producing cyclohexane, nor, or its ester from a fatty acid solution of cyclohexane at a high conversion rate.

There are no examples of electrochemical production of cyclohexanol, which is one of the raw materials for organic synthesis. For example, when cyclohexane is mixed with an acetone/sulfuric acid/aqueous solution and lead dioxide anodic oxidation is performed, a ring-opening reaction occurs and only lower fatty acids such as adipic acid, glutaric acid, and succinic acid and carbon dioxide gas are obtained. (Yok07ama, Bull,
chem, Soc, Jpn +8, 71
(1933)). Since this was reported, no research on electrochemical synthesis methods for partial oxidation of cyclohexane was conducted for a long time. However, in recent years, cyclohexane has been converted into Fe(lrl)-containing t-BuOH/
It has been reported that when mixed with H20/H (4! solution and electrolytically treated under oxygen pressure), the interaction between OH radicals generated at the cathode and dissolved cyclohexane becomes the first reaction, and cyclohexanone can be obtained at a high conversion rate. (R, Tom
ato and A, RigO, J, App, E
electrochem, .

10.549 (1980)). This is a rare example of electrolytic oxidation of cyclohexane in which the ring-opening reaction is extremely suppressed, but even in this case only trace amounts of cyclohexanol are produced.

〔the purpose〕

The present inventors have made extensive efforts to develop a method for electrochemically producing cyclohexanol or its ester from cyclohexane. As a result, the inventors have found that a high conversion rate can be obtained by adding a supporting electrolyte to a cyclohexane fatty acid solution and performing electrolysis. We have discovered that it is possible to synthesize cyclohexanol or its ester at a high rate, and have completed the present invention.

〔composition〕

That is, the present invention relates to a method for producing cyclohexanol or its ester, which is characterized by adding a supporting electrolyte to a cyclohexane fatty acid solution and performing electrolysis.

In the present invention, cyclohexane is electrochemically oxidized to cyclohexanol on the anode surface, and then this cyclohexanol is non-electrochemically combined with a solvent fatty acid to form an ester. A two-step reaction consisting of an electrochemical reaction and a non-electrochemical reaction, and a cyclohexyl group and an acyloxy group (a type in which the hydrogen bonded to the oxygen of the fatty acid is removed) are generated electrochemically on the anode surface between cyclohexane and the solvent fatty acid. Cyclohexyl ester, which is a cyclohexanol derivative, can be obtained at a high conversion rate from cyclohexane and a solvent fatty acid through a process such as a so-called electrochemical substitution reaction in which these groups combine in the same place to form an ester. . Also, if necessary,
Cyclohexanol can be easily obtained by hydrolyzing this ester using a conventional method.

The solvent used in the present invention is prepared by adding a supporting electrolyte to the fatty acid, and the preferred ratio is determined by the anode position in the solvent after the addition of the supporting tS, the solubility of cyclohexane, and the conversion rate to cyclohexanol or its ester. Therefore, it should be determined by experiment. In addition,
The standard for the anode potential is usually to obtain cyclohexyl acetate at a high conversion rate by dissolving about 1.5 cyclohexane to the saturated east electrode (SCE) and electrolyzing this solution under the above anode potential. Through experiments, it was found that the following solvent composition is sufficient. In other words, when examining the solvent composition that satisfies only the solubility conditions for cyclohexane, water/
The molar ratio of sulfuric acid is 220 or less, and the ratio of acetic acid is acetic acid/
It has been found that the molar fraction in the three-component system of sulfuric acid/water should be 0.70 or more. Next, cyclohexane was dissolved in the above-mentioned ratio in a solvent with this composition, and electrolysis was performed at an anodic potential of 25 volts against 8'CE to achieve a conversion rate of 50%.
It has been found that the molar ratio of water/sulfuric acid should be between 0.25 and 1.0 in order to obtain cyclohexyl acetate at a certain level.

The fatty acid used as a solvent is a monocarboxylic acid that is liquid at room temperature, and examples thereof include acetic acid and propionic acid.

It is also possible to use alkali or other metal salts of fatty acids as supporting electrolytes. In this case, the transition metal salt of a fatty acid is expected to act not only as a supporting electrolyte but also as a catalyst. This catalytic effect is expected since transition metals, in both inorganic and organic forms, are often used as catalysts in organic synthesis reactions.

As the anode used in the present invention, it is preferable to use a smooth platinum electrode, but any other electrode that is equivalent to this electrode in terms of overvoltage characteristics and catalytic ability may be used.

〔Example〕

Next, the present invention will be explained in detail by way of examples.

In Examples 1 to 3, the sample solution was prepared by mixing Schif-lohexane with acetic acid to which sulfuric acid and water were added as supporting electrolytes.
6, and this sample solution was electrolyzed at 30°C using a platinum electrode. The amount of sample solution used is 300 ml of acetic acid containing supporting electrolyte.
10 rnl of cyclohexane was added to the solution, and the total quantification was performed by gas chromatography.

Details of the experimental conditions and experimental results are shown in the table below. In the solvent composition column on the wood table, only the proportion of acetic acid is shown as the molar fraction in the ternary system of acetic acid/sulfuric acid/water, and the proportions of the other two components are shown as the molar ratio of both. Moreover, the conversion rate on the component side corresponds to the yield when the entire amount of cyclohexane is reacted. As can be seen from the reaction results shown in the table, cyclohexyl ester was obtained from cyclohexane at a high conversion rate of 40 to 50 mol.

Table 10.85 0.25 (2,5)
2.2 1 4920.88 1.0
2.55 (4,2) 3 463
0.73 0.50 (2,4) 1
．． 3 4 38341 The potential within the brackets indicates the initial value in constant current electrolysis.

The current density in ×2 brackets indicates the initial value in constant potential electrolysis.

〔effect〕

As explained above, according to the present invention, cyclohexanol or its ester can be obtained from cyclohexane by drowsiness chemical means at a high conversion rate.

Claims (1)

[Claims] (1) A method for producing cyclohexanol or its ester, which comprises adding a supporting electrolyte to a cyclohexane fatty acid solution and performing electrolysis.