JPH0660425B2 - Method for producing hydroquinone monoalkyl ethers - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing hydroquinone monoalkyl ethers.

Hydroquinone monoalkyl ethers are
It is useful as an intermediate for dyes, photographic sensitizers and the like. For example, JP-A-56-16475 and JP-A-54-22.
Examples of the use of hydroquinone monoalkyl ethers as intermediates are described in JP-A-371, JP-A-53-40767 and the like.

2. Description of the Related Art Generally, the following methods are typical for obtaining hydroquinone monoalkyl ethers.

(1) Hydroquinone and alkyl halide are dehydrohalogenated in the presence of alkali to obtain monoalkyl ethers.

J. Amer. Chem. Soc. 72 1413 (1950) (2) The desired monoalkyl ethers are obtained by dehydrating hydroquinone and alcohol in the presence of benzoquinone using an acidic dehydration catalyst.

SUMMARY OF THE INVENTION Problems to be Solved by the Invention The method (1) for dehydrohalogenating hydroquinone and alkyl halide in the presence of alkali to obtain monoalkyl ethers is In addition to ethers, dialkyl ethers that have been further alkylated can be obtained, and there is a drawback that only monoalkyl ethers cannot be selectively obtained.

Further, in the presence of benzoquinone in the presence of benzoquinone, hydroquinone and dehydration using an acidic dehydration catalyst to obtain the desired monoalkyl ethers The method (2) is not necessarily said to be obtained in high yield, also, The applicable alcohols are also limited and are not necessarily industrially advantageous.

Means for Solving the Problems The present inventors have dehydrated etherification of one hydroxyl group and alcohol of hydroquinone by dehydration etherification by hydrolyzing hydroquinone and alcohol as they are or by dissolving them in a solvent and carrying out an electrolytic reaction through electricity. The present invention has been completed by finding a method for selectively obtaining alkyl ethers.

According to this method, dehydrative etherification with p-alkoxyphenols in which one hydroxyl group of hydroquinones is substituted does not occur at all, and therefore only monoalkyl ethers are selectively obtained in high yield.

The reaction of dehydrating etherification of one hydroxyl group of hydroquinone and alcohol to obtain monoalkyl ethers by electrolytic reaction is completely new, and the reaction itself of dehydrating etherification of alcohol by electrolytic reaction is also novel. As far as the present inventors know, this is a completely new reaction.

Action The etherification reaction proceeds on the anode side, and hydrogen is generated from the cathode side.

As the electrolyte, iodine, sulfuric acid, hydrogen chloride or the like can be used.

The reaction potential is preferably in the range of 0.5 to 5 V between the anode and the reference electrode, and 50 V or less between the working electrode and the counter electrode.

The reaction temperature is usually in the range of 20 to 50 ° C, but when the solubility is poor depending on the solvent, the reaction temperature may be raised to the boiling point of the solvent.

Although alcohols to be reacted can be used as a solvent,
In addition, acetonitrile, acetone, ethers and the like can be used as the solvent.

Typical examples of alcohols used in the reaction include linear alkyl alcohols such as methanol, ethanol and n-butanol, branched alkyl alcohols such as isopropanol and s-butanol, chloroethanol, ethylene cyanohydrin and lactonitrile, Examples include substituted alcohols such as ethyl lactate.

Example A reactor for electrolytic reaction was a glass vessel, the solution was stirred using a stirrer, and platinum plates were used for the working electrode and the counter electrode. A silver-silver chloride electrode was used as the reference electrode, and the solvent used was the same as the solution used for the reaction.

Potentio Galvano Stat is Hokuto Denko HA-501,
The Coulomb amp hour meter used was Hokuto Denko HF-201.

Example 1 A magnetic stirrer was used in a 40 ml reactor, a platinum plate (length 36 mm, width 6 mm, thickness 0.2 mm) was used as a counter electrode for a working electrode, and a silver-silver chloride electrode was used as a reference electrode. I was there. 3.32 g of hydroquinone, 30 ml of ethanol and 0.78 g of iodine were charged and dissolved in this reactor to form a working electrode and a counter electrode.
A voltage of 30 V was applied and the temperature was around 30 ° C. for 18 hours, and a total of 12,000 coulombs of electricity was supplied. The product was quantified by gas chromatography using the internal standard method and confirmed by mass spectrometry.

The conversion was 86%, the selectivity of hydroquinone monoethyl ether was 99%, and the yield was 85%.

No by-product of hydroquinone diethyl ether was observed.

Example 2 3.32 g of hydroquinone, 30 ml of methanol, 0.39 g of iodine and 0.42 g of ethyl α-chloropropionate were charged and dissolved in the same reactor as in Example 1, and 15 V was applied to the working electrode and the counter electrode, and the temperature was 30. A total of 6,600 coulomb of electricity was supplied for about 23 hours at around ℃. The product was quantified by gas chromatography using the internal standard method and confirmed by mass spectrometry.

The conversion was 100%, the selectivity of hydroquinone monomethyl ether was 99%, and the yield was 99%.

No by-product of hydroquinone dimethyl ether was observed.

Example 3 In the same reactor as in Example 1, 3.32 g of hydroquinone, 30 ml of methanol and 0.2 g of sulfuric acid were charged and dissolved. Silver-
A voltage of 0.8 V was applied to the anode with respect to the reference electrode of the silver chloride electrode. The temperature was around 35 ° C. for 9 hours, and a total of 4,400 coulomb of electricity was applied. The product was quantified by gas chromatography using the internal standard method and confirmed by mass spectrometry.

The conversion was 94%, the selectivity of hydroquinone monomethyl ether was 99%, and the yield was 93%.

No by-product of hydroquinone dimethyl ether was observed.

Example 4 In the same reactor as in Example 1, 3.32 g of hydroquinone and 3.61 g of isopropyl alcohol were dissolved in 25 ml of the solvent acetonitrile, and 0.2 g of sulfuric acid was charged and dissolved. A voltage of 1.5 V was applied to the anode with respect to the reference electrode of the silver-silver chloride electrode. The temperature was around 55 ° C for 7 hours, and a total of 6,500 coulomb of electricity was applied. The product was quantified by gas chromatography using the internal standard method and confirmed by mass spectrometry.

The conversion was 87%, the selectivity of hydroquinone monoisopropyl ether was 99%, and the yield was 86%.

No by-product of hydroquinone diisopropyl ether was observed.

Examples 5 to 6 According to the above Examples 1 to 4, a reaction was carried out using 3.32 g of hydroquinone as a raw material and 30 ml of the following alcohol under the following conditions. Only monoalkyl ethers were selectively obtained in high yield. The results are shown in Table 1. In either case, formation of a disubstituted product in which two hydroxyl groups of hydroquinone were substituted was not observed.

Examples 7 to 8 According to the above Examples 1 to 4, hydroquinone (3.32 g) was used as a raw material, and the following 25 ml of acetonitrile was added, and the reaction was carried out under the following conditions. Only monoalkyl ethers were selectively obtained in high yield. The results are shown in Table 2. In either case,
Formation of a disubstituted product in which two hydroxyl groups of hydroquinone were replaced was not observed.

Example 9 Chlorhydroquinone 4.34 was added to a reactor similar to that of Example 1.
g, 30 ml of methanol and 0.2 g of sulfuric acid were charged and dissolved. A voltage of 1.9 V was applied to the anode with respect to the reference electrode of the silver-silver chloride electrode. The temperature was around 45 ° C for 4 hours, and a total of 2,640 coulomb of electricity was applied. The product was quantified by gas chromatography using the internal standard method and confirmed by mass spectrometry.

The conversion was 83%, the selectivity of chlorohydroquinone monomethyl ether was 99%, and the yield was 83%.

No by-product of chlorohydroquinone dimethyl ether was observed.

Example 10 The same reactor as in Example 1 was charged with methylhydroquinone 4.34.
g, 30 ml of ethanol and 0.4 g of sulfuric acid were charged and dissolved. A voltage of 1.9 V was applied to the anode with respect to the reference electrode of the silver-silver chloride electrode. The temperature was around 45 ° C for 4 hours, and a total of 2,640 coulomb of electricity was applied. The product was quantified by gas chromatography using the internal standard method and confirmed by mass spectrometry.

The conversion was 83%, the selectivity of methylhydroquinone monoethyl ether was 99%, and the yield was 64%.

No by-product of methylhydroquinone diethyl ether was observed.

As is clear from the above examples, by using the electrolytic reaction of the present invention, it is possible to selectively alkylate one hydroxyl group of hydroquinone in high yield using various alcohols.

By obtaining the target product with a high selectivity and a high yield, the separation step becomes unnecessary, and the facility can be simplified and the energy cost can be reduced, which is a great industrial contribution.

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Claims (1)

[Claims] 1. An alcohol selected from linear alkyl alcohols, branched alkyl alcohols and substituted alcohols in the presence of iodine, sulfuric acid or hydrogen chloride,
A method for producing hydroquinone monoalkyl ethers, characterized in that hydroquinone is electrolytically oxidized at an anode in the range of 0.5 to 5 V with respect to a reference electrode.