JPH0381249A - Production of 2,6-dimethyl-p-benzoquinone - Google Patents

Abstract

PURPOSE:To obtain the subject compound useful as a synthetic intermediate of a functional polymer or medical drug, etc., in high yield with using a small amount of catalyst and in high reaction speed by efficiently oxidizing 2,6- dimethylphenol with oxygen using a specific catalyst. CONSTITUTION:A catalyst composed of a copper compound and a various nitrogen compound, namely salt of hydroxylamines and an inorganic acid or a mixture of said amines and acid, or combination of oximes or a mixture of oximes and an inorganic acid is used to oxidize 2,6-dimethylphenol with oxygen preferably in a 1-8C lower aliphatic alcohol or a mixed solution of an aromatic hydrocarbon and a 1-8C lower aliphatic alcohol as a solvent to afford the aimed compound. Reaction temperature is preferably from room temperature to 200 deg.C, especially from room temperature to 80 deg.C. Besides, using ratio of the copper compound to hydroxylamines, etc., is 1mol the former copper compound to 0.3-3mol the latter compound.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing 2,6-dimethyl-p-benzoquinone, which is useful as a synthetic intermediate for functional polymers, pharmaceuticals, and the like.

More specifically, the present invention uses a catalyst consisting of a combination of a copper compound and various nitrogen compounds in the liquid phase, namely salts of hydroxylamines and inorganic acids or mixtures thereof or mixtures of oximes and inorganic acids, Using an aliphatic alcohol or a mixture of an aromatic hydrocarbon and a lower aliphatic alcohol as a solvent, 2,6-dimethylphenol (hereinafter abbreviated as DMP) is efficiently oxidized with oxygen to produce 2,6
The present invention relates to a method for producing -dimethyl-p-benzoquinone (hereinafter abbreviated as DMQ).

[Prior art]

DMQ is a functional polymer such as a liquid crystal polymer, but a high-efficiency synthesis method has not yet been established. Furthermore, many studies have been made on methods for producing benzoquinones by oxidizing alkyl-substituted phenols in one step. No.) Primary halous acid (
Special Publication No. 60-81135), hydrogen peroxide (Eur, P
at, Appl.

A method using an oxidizing agent such as 107176) has been proposed. However, even these methods have problems in terms of generation of harmful gases, use of expensive oxidizing agents, and generation of by-products.

For these reasons, methods using oxygen as an oxidizing agent have been studied,
Various catalyst systems have been proposed for this oxidation reaction, but
For example, a method using a cobalt complex as a catalyst (Japanese Patent Publication No. 56-2
No. 6647) has a high initial activity, but has the disadvantage that the catalyst life is extremely short. In addition, although high values for both reaction rate and selectivity have been obtained in the method using halogenated steel as a catalyst, there are various fundamental drawbacks that need to be resolved. In the method of oxidizing phenols using copper salt (Japanese Patent Application Laid-Open No. 49-36641),
The yield of benzoquinones is about 75%, and other by-products such as polyphenylene oxide are produced, and the benzoquinone must be separated from polymers that are difficult to process, so it cannot be said to be an efficient production method.

Method for oxidizing phenols in an organic solvent in the presence of a catalyst consisting of copper and halogen ions
No. 85) is an excellent method in terms of high yield, but because the activity of the catalyst is extremely low, it is necessary to carry out the reaction for a long time using a catalyst in an approximately equimolar amount to the phenol. This large amount of catalyst must be used repeatedly, which has fatal drawbacks such as increased utility consumption.

In order to improve these drawbacks, several patents (for example, JP-A-50-93931, JP-A-59-2,
No. 25137 or JP-A No. 63-280040), but in both cases, the basic problem is a method to facilitate the recycling use of the catalyst.There is no evidence of improvement in the catalytic activity itself. .

[Problem that the invention seeks to solve]

Therefore, as a result of extensive research into oxidation catalysts and oxidation reaction solvents for producing DMQ by oxidizing DMP with oxygen, the present inventors found that copper compounds and various nitrogen compounds,
That is, a catalyst consisting of a salt of hydroxylamine and an inorganic acid or a mixture thereof, or a combination of oximes or a mixture of oximes and an inorganic acid is used, and a lower aliphatic alcohol having 1 to 8 carbon atoms or an aromatic carbonization is used as a solvent. We have discovered that the desired DMQ can be produced in high yield by using a mixture of hydrogen and a lower aliphatic alcohol having 1 to 8 carbon atoms, and based on this finding, we have accomplished the present invention.

[Means for solving problems]

That is, the present invention provides a method for producing DMQ by oxidizing DMP with oxygen. It is characterized by using a catalyst consisting of a combination of a mixture with an acid, and using a mixture of a lower aliphatic alcohol having 1 to 8 carbon atoms or an aromatic hydrocarbon and a lower aliphatic alcohol having 1 to 8 carbon atoms as a solvent. The present invention provides a method for manufacturing DMQ.

In the present invention, DMP is dissolved in a mixed solvent of a lower aliphatic alcohol having 1 to 8 carbon atoms or an aromatic hydrocarbon and a lower aliphatic alcohol having 1 to 8 carbon atoms, and molecular oxygen and a catalytic amount of a copper compound and This is easily achieved by simple stirring at room temperature to 200°C in the presence of various nitrogen compounds, i.e., salts of hydroxylamines and inorganic acids or mixtures thereof, or oximes or mixtures of oximes and inorganic acids. This is a simple and safe oxidation method.

In the present invention, in order to oxidize DMP, molecular oxygen is used as an oxidizing agent, and a copper compound and various nitrogen compounds as catalysts, such as salts of hydroxylamines and inorganic acids or mixtures thereof; and inorganic acids. As the molecular oxygen source, either pure oxygen gas or air may be used, and it is effective in the range of normal pressure to 30 kg/all. As the copper compound used as a component of the catalyst, inorganic salts, organic salts, etc. can be used and there are no particular restrictions, but chlorides such as cuprous chloride and cupric chloride show particularly good reaction results. Hydroxylamines, which are nitrogen compounds used as other components of the catalyst, include hydroxylamine itself, N,N-dialkylhydroxylamines such as N,N-dimethylhydroxylamine, and N-
Various hydroxylamine derivatives such as N-alkylhydroxylamines such as methylhydroxylamine and O-alkylhydroxylamines such as O-methylhydroxylamine can be used, but in particular hydroxylamine, hydroxyurea or low molecular weight N, N-Dialkylhydroxylamines show good reaction results. Regarding oximes, b) δ' dialkyl ketones such as Banji acetone, methyl ethyl ketone, diethyl ketone, etc.
Any ketones such as cyclic ketones such as cyclohexanone and cyclooctanone, aromatic ketones such as acetophenone and propiophenone, diketones such as diacetyl and acetylacetone, and cyclic diketones such as dimedone, or formaldehyde, acetaldehyde, and propion. Aliphatic aldehydes such as aldehydes, benzaldehydes,
Oximes of any aldehydes such as aromatic aldehydes such as phenylacetaldehyde can be used, but oximes with relatively low molecular weight such as acetaldoxime, benzaldoxime, acetone oxime, and 2-butanone oxime are particularly suitable. give a reaction score. In addition, when using salts with these inorganic acids, various inorganic acids such as sulfuric acid and halogen acid can be used, and there is no particular restriction, but hydrochloric acid or sulfuric acid gives relatively good results. give. The addition of this inorganic acid is not essential, and sufficient catalytic activity can be obtained with a system of copper compounds and oximes, but the catalytic activity is often improved by further adding an inorganic acid. It is not necessary to prepare and use a mixture of oya, uamia, oya, amine, and inorganic acid in advance, and they may be added separately, and in either case, there is no particular restriction on the composition ratio of each. However, a range of 0.2 to 5 moles of the inorganic acid per mole of hydroxylamines and oximes gives good reaction results. There is no particular restriction on the amount of hydroxylamines and oximes to be used with respect to the copper compound, but if the amount is too small or too large, the reaction rate will be low, so in any case, 0.3 to 3 mol per 1 mol of the copper compound. The amount of the catalyst obtained in this way is not particularly limited, but if it is too small, the reaction rate will be low, and if it is too large, problems will arise with separation after the reaction.
Use of 0.01 to 0.1 mol per mol of MP gives preferable reaction results.

Regarding the solvent used in the reaction in the method of the present invention, lower aliphatic alcohols having 1 to 8 carbon atoms include methanol, ethanol, 1-propanol, isopropanol, 1-butano-≦1,2-butanol, ta
Examples include rt-butanol, 1-amyl alcohol, 2-amyl alcohol, 3-amyl alcohol, 5ec-amyl alcohol, tart-amyl alcohol, l-hexanol, 1-octatool, 2-octatool, etc. Although not limited, tertiary alcohols such as tert-butanol, tert-amyl alcohol give preferred results. When using a mixed solvent of aromatic hydrocarbons and lower aliphatic alcohols having 1 to 8 carbon atoms, there are no particular restrictions on the aromatic hydrocarbons; Those that are stable against oxidation are preferred. At this time, a mixture of one or more of the above-mentioned lower aliphatic alcohols having 1 to 8 carbon atoms and one or more aromatic hydrocarbons is used as a solvent. These solvents have excellent effects on dissolving copper compounds as catalysts, hydroxylamines, oximes, and/or inorganic acids, DMP as raw materials, and oxygen, and can dissolve the desired DMQ simply by bringing them into contact. Generate extremely effectively. The composition ratio of aromatic ＼嘱--I-1''-hydrogen and lower aliphatic alcohol cannot be determined unconditionally because it varies depending on the combination, but the capacity of lower aliphatic alcohol to aromatic hydrocarbon The ratio is preferably 0.2 to 1.5, particularly preferably 0.25 to 0.8.

The above catalysts can be used by directly dissolving them in these mixed solvents, but they can also be used as an aqueous solution. In addition, as the aliphatic alcohol having 1 to 8 carbon atoms used in this case, there is no particular problem as long as it has low water solubility, and butanol, pentanol, hexanol, heptatool, octatool, etc. containing various isomers are used. It is possible. In either case, D dissolved in the solvent
In order to efficiently bring the MP into contact with the catalyst dissolved in the aqueous phase and the oxygen in the gas phase, it is necessary to provide an efficient stirring device and aeration device.

The reaction temperature in the method of the present invention can be carried out at room temperature to around 200°C, but if the temperature is too low, the reaction rate will be slow, and on the other hand, the reaction temperature will be too high, as the loss of solvent or side reactions will increase. Preferably, the temperature is 80°C. Although the reaction time depends on the reaction temperature, oxygen pressure, and amount of catalyst used, 1 to 10 hours is usually sufficient.

〔Effect of the invention〕

According to the method of the present invention, copper compounds such as cupric chloride, which are inexpensive commercially available general reagents, and nitrogen compounds such as hydroxylamine and acetone oxime are used as catalysts, and
-8 lower aliphatic alcohols or aromatic hydrocarbons and lower aliphatic alcohols having 1 to 8 carbon atoms when the reaction is carried out as a solvent and the catalyst as an aqueous solution, the above-mentioned mixed solution is used. Or carbon number 1~
In one step, DMP is oxidized with molecular oxygen using an aliphatic alcohol of No. 8 with relatively low water solubility as a solvent.
In addition, it is possible to obtain DMQ at extremely high reaction rates and yields, and there is no need to circulate a large amount of catalyst, which was a drawback of the conventional method, so it is suitable as an industrial method for producing MQ.

Since the activity of the catalyst used in the present invention is extremely high,
It is sufficient to use a small amount of the catalyst, and it is not necessarily necessary to reuse the catalyst in a circular manner; however, if this is necessary, the catalyst can be used in the form of an aqueous solution. In this case, under stirring during the reaction, in a mixed solvent system, due to the lipophilicity of aromatic hydrocarbons and the hydrophilicity of lower aliphatic alcohols, aliphatic alcohols that are poorly water soluble are replaced with long-chain alkyl groups in solvents. Due to the lipophilicity and the hydrophilicity of the hydroxyl group, it becomes well suspended with the catalyst in the aqueous phase, allowing the three-phase reaction of aqueous phase - organic phase - gas phase to proceed smoothly, but stirring is not recommended after one reaction is completed. When stopped, it rapidly separates into an organic phase and an aqueous phase,
The catalyst in the aqueous phase can be separated and recovered for reuse, and at the same time, the solvent can be removed from the organic phase by means such as distillation, making it easy to isolate the product DMQ.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. still,
The embodiments of the present invention are representative examples for easier understanding of the present invention.

The present invention is not limited to these.

In addition, the conversion rate of DMP and the yield of DMQ shown in the following Examples and Comparative Examples were determined by gas chromatography using O-dichlorobenzene as an internal standard.

Examples 1 to 7 D M P 2 m in a glass container with an internal volume of 10 m1
mol, 0.2 mmol of cupric chloride dihydrate as a catalyst and specified amounts of various additives, and 2 m of n-hexanol.
1 as a solvent, the reaction temperature was 60°C, and the oxygen pressure was 86°C.
The reaction was carried out while maintaining the temperature at 0 mmHH, and the amount of oxygen absorbed was measured using a gas villet. After oxygen absorption has almost stopped,
The reaction was further carried out for about 1 to 2 hours to complete the reaction, and the products in the first reaction solution were analyzed. Table 1 shows the conversion rate of DMP and the yield of DMQ produced.

Comparative Examples 1 and 2 Reactions were carried out in the same manner as in Examples 1 to 7 without adding an additive or using lithium chloride as an additive. DM
Table 1 shows the conversion rate of P and the yield of DMQ produced.

Table 1 Additive DMP rate DMQ yield Total reaction rate (+l
a+ol) (%) (%) (h) Example 1 ^0 (0,4) 100 45.4
32 AO(0,6) 100 43
．． 7 33 AO(0,2)+HC1(0,4
) 89.145.5 54 AO(0,4
)+HC1(0,4) 95.452.9 4
5 AO(0,6)+HC1(0,6) 100
45.1 36 HAH(0,4)
98.145.8 37 HAS(0,2)
100 50.5 3 Comparative Example 1 30.1 7.9 52
LiC1(0,2) 61.539.9
5 In addition, the abbreviations used for additives in Table 1 indicate the following compounds.

HAH = hydroxylamine hydrochloride (NH, OH, HC
I), HAS=hydroxylamine sulfate (NH,0H
)t, H2S04), AO = Acetone Oki Kurecom (CH
,)2C=NOH) and 36% aqueous hydrochloric acid solution was used as HCI.

Examples 8 to 10 In Examples 1 to 7, cupric chloride dichloride was added to 0°1+a
mo1. Using 2 ml of tertiary butanol as a solvent, the reaction was carried out in the same manner as in Examples 1 to 7 at a reaction temperature of 40°C. D
Table 2 shows the conversion rate of MP and the yield of DMQ produced.

Comparative Examples 3-4 In the same manner as Examples 8-10, with or without adding additives
The reaction was carried out using lithium chloride or diethylamine hydrochloride as an additive. Table 2 shows the conversion rate of DMP and the yield of DMQ produced.

Table 2 Calorie additive DNP conversion DMQ yield Total reaction time fraction (011101)
(%) (%) (h) Example 8 AO(0,2)+HC1(0,2) 78,7
32.3 59) IAH(0,2)
100 73.2 310)IAS(0
,1) 100 82.5 2 Comparative Example 3 LiC1(0,1) 10.1 −
54 (C,Hs)2NH-HCI(0,2)
42.6 3.6 5 Note that in Table 2, the abbreviations used for converting agents indicate the following compounds.

HAH = hydroxylamine hydrochloride (NH,OH,)I
c1), HAS=hydroxylamine sulfate (N)I*
0H)z.

)+2SQ,), AO=acetone oxime ((C)I,
), C=NOH) and 36% aqueous hydrochloric acid solution was used as HCI.

Examples 11 to 3 In Example 9, reactions were carried out in the same manner as in Example 9, using various aliphatic alcohols instead of tertiary butanol as the solvent. DM generated when the conversion rate of DMP decreases by 1
The yield of Q is shown in Table 3.

Table 3 Solvent DMPi conversion rate DMQ yield Total reaction time (ml) (
%) (%) (h) Example 11 1-Pr0H (2) 100 77.3
2.512 1-BuOl((2) 1
00 64.2 2.513 2-PeOH(2)
98.471.6 2.5 In Table 3, the abbreviations used for solvents indicate the following compounds.

1-Pro)I=isopropanol, 1-BuOH=isobutyl alcohol and 2-PeOH:2-pentanol.

Examples 14-19 In Example 10, various aliphatic alcohols or a mixed solvent of an aliphatic alcohol and an aromatic hydrocarbon were used instead of tertiary butanol as the solvent, and Example IO
The reaction was carried out in the same manner. Table 4 shows the conversion rate of DMP and the yield of DMQ produced.

Table 4 Solvent DMP-i conversion rate DMQ yield Total pressure 1 hour blade (ml)
(%) (%) (h) Example 14 1-Pr0H (2) 100 77.
4 2.515 2-PeOH(2) 1
00 82.4 2.516 t-AmOH(2)
100 85.8 217 Tol(1
,5)+1-Pro)I(0,5) 100 88.2
218 Tol(1,5)+t-BuOH(0,5
) 100 86.5 2 Example 20 In Example 9, isopropanol and cupric chloride dihydrate were used as the solvent instead of tertiary butanol.
When a reaction was carried out for 2 hours in the same manner as in Example 9 using a+mol, a DMP conversion of 96.2% and a DMQ yield of 64.2% were obtained.

Examples 21 to 23 In Example 20, 0 to 1 mmol of hydroxylamine sulfate was used instead of 0 to 2 mmol of hydroxylamine hydrochloride as an additive, and various aliphatic alcohols or aliphatic alcohols and aromatic hydrocarbons were used as solvents. The reaction was carried out in the same manner as in Example 20 using a mixed solvent of . Table 5 shows the conversion rate of DMP and the yield of DMQ produced.

Table 5 Solvent DMPi conversion rate DMQ yield Total reaction time (ml)
(%) (%) (h) Example 21 1-Pr0H(2) 98,5 6
6.8 222 t-BuOH (2)
100 84.1 223 Tol(1,0)+1
-Pr0H(1,0) 100 81.6 2 special,
Note Applicant Industrial Technology 1: Masaru Nagasugiura, Numaga

Claims (2)

[Claims] (1) Oxygen oxidation of 2,6-dimethylphenol to 2,
In producing 6-dimethyl-p-benzoquinone,
It is characterized by using a catalyst consisting of a combination of a copper compound and various nitrogen compounds, i.e., salts of hydroxylamines and inorganic acids, or mixtures thereof, or oximes or mixtures of oximes and inorganic acids2,6. -Method for producing dimethyl-p-benzoquinone. (2) 2,6-dimethylphenol is reacted with a catalyst consisting of a copper compound and various nitrogen compounds, i.e., salts of hydroxylamines and inorganic acids, or mixtures thereof, or combinations of oximes or mixtures of oximes and inorganic acids. , a method for producing 2,6-dimethyl-p-benzoquinone by oxygen oxidation, a mixture of a lower aliphatic alcohol having 1 to 8 carbon atoms or an aromatic hydrocarbon and a lower aliphatic alcohol having 1 to 8 carbon atoms as a solvent. A method for producing 2,6-dimethyl-p-benzoquinone, characterized in that a liquid is used.