JPS62190139A - Oxidation of glycol - Google Patents

Abstract

PURPOSE:In the oxidation of glycol with aqueous periodic acid, the aqueous iodic acid as a by-product of the oxidation is electrolytically oxidized and the regenerated periodic acid is reused to effect the oxidation with industrial advantage. CONSTITUTION:i) A compound of formula I (R1-R4 are H, alkyl, aryl, alkoxycarbonyl where R1-R4 are not H or alkoxycarbonyl simultaneously) is oxidized with periodic acid into the objective compounds of formula II and formula III. ii) The products are separated from the reaction mixture. iii) The aqueous iodic acid which is recovered in the formula process as a by-product is electrolytically oxidized to regenerate periodic acid. iv) The acid is recycled to the process i) repeatedly to solve the problems of economy in the use of the acid in large amounts, the safety in the transportation and the post treatment of the by-products.

Description

[Detailed description of the invention] Fields of use on Kushirai〉 The present invention relates to an improved method for oxidizing glycols.

Prior art> A periodic acid aqueous solution has been known as an oxidizing agent used for the cleavage of glycols, and it is also well known that the reaction proceeds with bending oxidation action and good elongation. ("Latest-i' lt+Chemistry J H, O, Ho
use).

However, in order to carry out the oxidation of glycol using an aqueous solution of i16 iodohydric acid on a scale of one cup, a large amount of aqueous periodic acid is required, and an aqueous solution of iodic acid in human urine is generated as a by-product. For this reason, ■ economic problems associated with using a large amount of periodic acid aqueous solution, ■ safety measures for transporting iodic acid water I4I due to the use of Ogaki, and ■ problems with by-product iodic acid aqueous solution generated in Ogaki. It had the same characteristics that are extremely important industrially, such as during processing.

Problems that the invention seeks to solve> For these reasons, in the oxidation of glycols using periodic acid water gh as an oxidizing agent, it is possible to carry out the oxidation reaction industrially advantageously without causing the above-mentioned problems. As a result of extensive research, it was discovered that the objectives could be achieved by regenerating a rigid aqueous iodic acid solution through the reaction and reusing it as an oxidizing agent, leading to the present invention.

Means for Solving the Problems> That is, the present invention solves the problems of the general formula (1) (wherein R+, R2, Rs and R4 are hydrogen atoms,
Indicates an alkyl group, an aryl group or an alkoxycarbonyl group. However, R1, R2, R3 and R4 are never hydrogen atoms or alkoxycarbonyl groups at the same time. ) is reacted with an aqueous periodic acid solution to form the general formulas (n) and (III) (II).
(m) A step of obtaining an oxidation product represented by (in the above formula, Rt, Rz, Ra and R4 have the same meanings as above); Glycols characterized by comprising the following steps: (1) regenerating the periodic acid aqueous solution by electrolytically oxidizing the iodic acid aqueous solution recovered in the process; (1) recycling the periodic acid aqueous solution obtained in (2) to the process (2). The present invention provides a method for oxidizing.

The glycols applied to the present invention are those represented by the general formula (summer), and the alkyl groups in each substituent include methyl, ethyl, n-butyl, isopentyl, n-
Oxyl, cyclopropyl, 2,2-dimethyl-8-methoxycarbonylcycloprobyl, cyclohexyl, menthyl, hydroxycarbonyloctyl, etc., and aryl groups include phenyl, tolyl, chlorophenyl, 8.
Examples of the alkoxycarbonyl group include 4-methylenedioxyphenyl, methoxycarbonyl, n-butoxycarbonyl, and p-menthoxycarbonyl.

In such an oxidation reaction of glycols with an aqueous periodic acid solution, the degree of e of the aqueous periodic acid solution used is 80 times ff11 or more in order to effectively separate the oxidation product and the aqueous iodic acid solution after the reaction is completed. This is desirable.

If this separation is insufficient and oxidation products or solvents are mixed into the aqueous iodic acid solution, it will have an adverse effect on the regeneration of the aqueous periodic acid solution.

The amount of periodic acid used is at least 1 mole, preferably 1.1 to 2 moles, of periodic acid relative to the glycols. Of course, there is no negative effect on the reaction if the amount is more than 2 times the amount by mole, but it is not as effective as it should be and is economically disadvantageous.

In this oxidation reaction, a solvent can be used if the raw material glycols are not soluble in water and, as a result, the reaction progresses slowly.

When a solvent is used, any organic solvent may be used without particular limitation as long as it is inert to the reaction, but alcoholic solvents such as methanol and ethanol, acetonitrile, and the like are preferably used.

The amount of the solvent to be used is not particularly limited, but is generally up to about 10 moles, preferably 1 to 8 moles.

The reaction temperature in the oxidation reaction varies depending on the type of glycol used and other conditions, but is generally 0 to 70".
It is C.

This oxidation reaction produces oxidation products from glycols and an aqueous iodic acid solution as a by-product.

This separation of the oxidation product and the iodic acid aqueous solution is generally performed by dispersing the oxidation reaction solution, but separation can be accelerated by using a solvent that is immiscible with the iodic acid aqueous solution per dispersion. I can do it. As the organic solvent for this purpose, aromatic solvents such as toluene or halogen solvents such as dichloroethane are preferable.

The iodic acid aqueous solution thus recovered is electrolytically oxidized and regenerated into a periodic acid aqueous solution.

This electrolytic oxidation method is not particularly limited and may be carried out according to a known method, but is generally carried out by the following method.

In this electrolytic oxidation, the working electrode is an anode, and the counter electrode is a cathode.The material of each electrode is lead dioxide for the anode, iron, stainless steel, platinum, graphite, etc. for the cathode, and the distance between the electrodes is It is usually 50 mm or less.

In addition, during this deoxidation, the periodic acid aqueous solution produced may be reduced at the cathode, so it is desirable to insert a diaphragm between the anode and 1I2-8i11. As a diaphragm for this purpose, a cation exchange membrane, an anion exchange membrane, a magnetic P/Ii membrane, etc. can be used.

Where a diaphragm is used, a catholyte is required, and the catholyte can be an aqueous solution of a water-soluble inorganic base such as sodium hydroxide, an aqueous solution of a mineral acid such as sulfuric acid, or an aqueous solution of a water-soluble salt such as common salt. used.

The current density of the anode is usually less than 100 A/dni'.

Preferably it is 0.5 to 40 A/d.

Periodic acid is not particularly limited, and periodic acid is produced depending on the electric group, but generally it is 1 mol or more of 2F, preferably 1 mol of 2F to 6F, based on iopuric acid.

The reaction is usually carried out at a temperature of 0 to 70°C.

Through this electrolytic oxidation, the by-product iodic acid aqueous solution recovered in the previous step is regenerated into a periodic acid aqueous solution, and this periodic acid aqueous solution is recycled as it is as an oxidizing agent in the first step of oxidizing glycols.

For recycling, only the reconstituted aqueous periodic acid may be used as the oxidizing agent, or, if necessary, fresh aqueous periodic acid may be used together with it.

<Effects of the Invention> Thus, by following the method of the present invention, economical problems associated with the use of periodic acid aqueous solution in heavy storms and safety problems associated with transportation, which have traditionally been considered major problems, can be avoided. Furthermore, the problem of processing the by-product iodic acid aqueous solution was solved all at once, and it became possible to repeatedly use the periodic acid aqueous solution used initially, which was extremely advantageous from an industrial perspective. Can oxidize glycols.

<Example> The present invention will be explained below with reference to Examples.

Example 1 (a) Tartaric acid G! -←)-Menthyl ester (hereinafter referred to as cymentyl tartrate) l 07.8 f and acetonitrile 107.89 g were placed in a flask equipped with a stirrer, a thermometer and a reflux condenser, and nitrogen gas was passed through it. An iodic acid aqueous solution of 110.7 F (periodic acid content: 45.3%) is added dropwise while maintaining the reaction source pi at 20 to 80°C. The reaction is complete within 2 hours. After the reaction is complete, 215.69 g of toluene is added, stirred, and then separated. The toluene layer is washed with an aqueous sodium carbonate solution and concentrated to give glyoxylic acid! -(he)-menthyl ester hydrate (hereinafter referred to as menthyl glyoxylate) 120
F (contains 1 liter, 85.9%) is obtained. Menthyl glyoxylate can be crystallized from an n-hexane-water system and purified. The recovered iodic acid aqueous solution was 121.8F.
(Contains iodic acid; m40.o%). This iodic acid aqueous solution is electrolytically regenerated by the following method.

(b) Lead dioxide electric (effective electrode area 82d), iron electrode (effective m-face 82d), fluororesin cation exchange membrane (Celemion CMF: manufactured by Asahi Glass Co., Ltd., effective surface Jf11)
The reaction was carried out in the following manner using an electrolytic cell equipped with B2cj) and having a distance between electrodes of 20 mm.

The recovered iodine aqueous solution is added to the anode side, and the 2N sodium hydroxide aqueous solution 1009 is added to the cathode side. The reaction is carried out using constant current electrolysis at 4 A, and the reaction temperature is maintained at 20-50°C.

It passes 1.2 times the electric charge. After the reaction is completed, an aqueous periodic acid solution of 96.7F (Venus 47.6%) is obtained.

(C) Using the periodic acid aqueous solution thus collected, the same reaction and recovery process as above was repeated.

Table 1 shows the results of the recycling experiment.

Table 1 Example 2 (a) A periodic acid aqueous solution of 105.7 F (49.8 F containing periodic acid) is charged into a flask equipped with a stirrer, a thermometer, and a rapid flow cooler, and nitrogen gas is passed through the flask. Keep the internal temperature of the flask between 00 and 5°C, and add 1-(8,4
60 g of -methylenedioxyphenyl)propane-2,8-diol (hereinafter referred to as isosafrol diol) are added. The reaction is complete within 2 hours.

After the reaction is complete, 150v of toluene is added, stirred, and then separated. The toluene layer was washed with an aqueous sodium carbonate solution and then condensed to give 8.4-methylenedioxybenzaldehyde (hereinafter referred to as heliotropine)58. Of (includes 6
B, 8%). Heliotrobin is distilled or dehydrated (
The iodic acid content was 87.0%. This iodine frequency aqueous solution is electrolytically regenerated by the following method.

(b) Using the electrolytic cell used in Example 1, a reaction was carried out in the following manner.

Add the recovered iodic acid aqueous solution to the 11M electrode side, and add 2N sodium hydroxide aqueous solution 100F to the cathode side. The reaction is 4A
The reaction temperature is maintained at 20° to 50°C. After the reaction, a 92.8 F (containing 45.8 F) aqueous solution of iodic acid was obtained using a 1.75-fold ratio manufactured by Riron Denkisha.

(C) Using the periodic acid aqueous solution thus recovered, the same nuclear reaction and recovery treatment as above were repeated.

Table 2 shows the results of the recycling experiment.

Table-2

Claims (4)

[Claims] (1) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. (R_4 cannot be a hydrogen atom or an alkoxycarbonyl group at the same time.) By reacting the glycols represented by the following with an aqueous periodic acid solution, the general formulas ▲There are mathematical formulas, chemical formulas, tables, etc.▼ and ▲mathematical formulas, chemical formulas, tables, etc. etc. ▼ (In the above formula, R_1, R_2, R_3 and R_4 have the same meanings as above) A step of obtaining an oxidation product represented by (2) separating the oxidation product from the oxidation reaction solution; (3) a step of electrolytically oxidizing the iodic acid aqueous solution recovered in step (2) to regenerate the periodic acid aqueous solution; (4) A method for oxidizing glycols, comprising the steps of recycling the periodic acid aqueous solution obtained in (3) to the step (1).