CN108238947B - Method for preparing o-nitrobenzoic acid by oxidizing o-nitrotoluene with oxygen without catalyst - Google Patents
Method for preparing o-nitrobenzoic acid by oxidizing o-nitrotoluene with oxygen without catalyst Download PDFInfo
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Abstract
A method for preparing o-nitrobenzoic acid by oxidizing o-nitrotoluene without catalyst oxygen, relating to a method for preparing o-nitrobenzoic acid. Under the condition of not adding any catalyst, taking o-nitrotoluene as a raw material, taking oxygen as an oxidant and sodium hydroxide as alkali, reacting for 5-72 hours in solvent alcohol or aqueous solution thereof at the reaction temperature of 25-85 ℃, and obtaining the o-nitrobenzoic acid through post-treatment, separation and purification. The method does not need a catalyst; the raw materials and the solvent are low in price; the reaction temperature is moderate; easy production control, high yield up to more than 90 percent, suitability for mass preparation and industrialization and wide application prospect.
Description
Technical Field
The invention relates to a preparation method of o-nitrobenzoic acid, in particular to a method for preparing o-nitrobenzoic acid by oxidizing o-nitrotoluene with oxygen without a catalyst.
Background
The o-nitrobenzoic acid is an important organic synthesis intermediate and is widely applied to the fields of dye, medicine, food, organic synthesis and the like. The existing method for synthesizing o-nitrobenzoic acid is mainly potassium permanganate oxidation, sodium dichromate oxidation, NaClO oxidation, nitric acid oxidation or oxidation with addition of other transition metal and noble metal catalysts (Letters in Drug Design & Discovery,2013,10, 369; Applied organic Chemistry,2015,29, 276; Tetrahedron,2012,68, 9763; Catalysis Communications,2012,27, 124; Hangzhou chemical engineering, 1996.2.44). The method mainly uses high-valence manganese, chromium or chlorate, has serious environmental pollution problems and can generate a large amount of solid wastes; or nitric acid with strong oxidizing property and strong acidity, and severe corrosion can be caused to reaction equipment by death; and hydrogen peroxide, which is unstable and has an explosion hazard. These problems have greatly limited their industrial application.
The literature reports a method for synthesizing o-nitrobenzoic acid by catalyzing oxygen to oxidize o-nitrotoluene in an alkaline medium by using anhydrous methanol and methanol-benzene as solvents and selecting metal phthalocyanine as a biomimetic catalyst (fine chemical engineering, 1998,1, 45; fine chemical engineering, 2004,21, 474; CN 1944396A, published Japanese 2007-04-11; CN 1243717, granted bulletin date: 2006-03-01). The method has the disadvantages that anhydrous methanol or methanol-benzene is used as a solvent, the operation (reaction or distillation) of the anhydrous methanol under the pure oxygen condition has potential explosion hazard, and the methanol has great toxicity to optic nerves; moreover, benzene has significant hematologic and neurotoxicity, which poses a potential threat to the health of laboratory and industrial operators. In addition, a method for synthesizing o-nitrobenzoic acid by catalyzing oxygen to oxidize o-nitrotoluene in an alkaline medium by using 80% ethanol aqueous solution as a solvent and selecting ferriporphyrin chloride as a biomimetic catalyst is also reported (journal of chemical engineering, 2007,58, 3053). The method solves the problems of equipment corrosion, environmental pollution and the like in the preparation of the o-nitrobenzoic acid in an acidic medium. In addition, the literature (appl. Catal A; general.2005,282,55) and many patents (CN 1521153A, CN 1453259, CN 1333200) also disclose and report the method for preparing benzyl alcohol, benzaldehyde and benzoic acid and derivatives thereof by oxidizing toluene and derivatives thereof with air as an oxidizing agent by using metalloporphyrin as a catalyst, but the problems of low conversion rate, poor selectivity and difficult separation of products and mixtures are generally existed. Professor laughing 2014 also discloses (CN 103755520 a) a method for producing benzyl alcohol, aldehyde and acid by using air to oxidize substituted toluene based on gas-liquid-solid multiple reaction separation synchronous reactor catalyzed by transition metal porphyrin, wherein the method generates a mixture of three products and takes the production of the benzyl alcohol and the aldehyde as a main purpose. All of the above published reports require metal phthalocyanine or metal porphyrin as a catalyst, and the industrial application thereof is limited due to problems of low yield, difficulty in separation and purification, consumption of a large amount of organic solvent, and the like in the synthesis of such a catalyst.
In summary, the conventional chemical oxidation method, catalytic oxidation method, or biomimetic catalytic oxidation method still have problems such as heavy metal pollution, environmental pollution, or difficulty in synthesizing catalyst, and the like, which limits the industrial application thereof, especially in the fields of medicine and food industry with heavy metal residue requirement and strict requirements thereof. Therefore, the improvement of the current method is urgently needed, a green and environment-friendly process method is developed to solve the problems in the current process, the production cost is reduced, and the industrial application range is expanded.
Disclosure of Invention
The invention aims to provide a method for preparing o-nitrobenzoic acid by oxidizing o-nitrotoluene with oxygen, which does not need a catalyst, has almost no toxicity, is safe to operate, has high yield and low cost.
A method for preparing o-nitrobenzoic acid by oxidizing o-nitrotoluene without catalyst oxygen is characterized by comprising the following steps: under the condition of not adding any catalyst, taking o-nitrotoluene as a raw material, taking oxygen as an oxidant and sodium hydroxide as alkali, reacting for 5-72 hours in solvent alcohol or aqueous solution thereof at the reaction temperature of 25-85 ℃, and obtaining the o-nitrobenzoic acid through post-treatment, separation and purification.
The method for preparing the o-nitrobenzoic acid by oxidizing the o-nitrotoluene with the oxygen is characterized in that a target product can be obtained without adding any catalyst.
The method for preparing the o-nitrobenzoic acid by oxidizing the o-nitrotoluene with the oxygen is characterized in that the concentration of the o-nitrotoluene serving as a raw material is 0.3-3.0mol/L, preferably 0.5-2.0mol/L, and preferably 0.5-0.6 mol/L.
The method for preparing the o-nitrobenzoic acid by oxidizing the o-nitrotoluene with the oxygen is characterized in that the concentration of the sodium hydroxide is 0.6-5.0mol/L, preferably 1.0-4.5 mol/L.
The method for preparing the o-nitrobenzoic acid by oxidizing the o-nitrotoluene with the oxygen is characterized in that the oxygen pressure is 0.1-2.0MPa, preferably 0.1-1.8MPa, and further preferably 1.0-1.8 MPa.
The method for preparing the o-nitrobenzoic acid by oxidizing the o-nitrotoluene with the oxygen is characterized in that the used solvent is methanol, ethanol, isopropanol and an aqueous solution thereof, the volume percentage of water in the aqueous solution is 0-50%, and the preferred solvent is ethanol.
The method for preparing the o-nitrobenzoic acid by oxidizing the o-nitrotoluene with the oxygen is characterized in that the reaction temperature is 25-85 ℃, and preferably 55-65 ℃.
The method for preparing the o-nitrobenzoic acid by oxidizing the o-nitrotoluene with the oxygen is characterized in that the reaction time is 5 to 72 hours, preferably 12 to 36 hours.
The method for preparing the o-nitrobenzoic acid by oxidizing the o-nitrotoluene with the oxygen is characterized in that neutralization reaction liquid is carried out after the reaction until the pH value is 1-7, and the pH value is preferably 2-4.
The method comprises the following steps: adding o-nitrotoluene and sodium hydroxide into a high-pressure kettle, and adding a solvent; introducing oxygen after multiple times of oxygen exchange, controlling the temperature to react, adding a solvent to dilute after the reaction, neutralizing the pH value of the reaction mixed solution, removing the solvent under reduced pressure, adding ethyl acetate, drying, filtering, and separating by a chromatographic column.
Compared with the prior art, the invention has the beneficial effects that:
(1) compared with a biomimetic catalytic oxidation method, the method does not need to use a catalyst, avoids the problems of difficult synthesis and purification of the biomimetic catalyst and consumption of a large amount of organic solvent, and reduces the cost;
(2) pure oxygen is used as an oxidant, so that the method is green and environment-friendly, and avoids the pollution of solid waste and heavy metal to the environment in a chemical oxidation method and a catalytic oxidation method;
(3) pure oxygen is used as an oxidant to react in a closed high-pressure kettle, so that potential explosion hazard existing in a mixture of an organic solvent and oxygen can be effectively avoided; the oxidation efficiency is improved, and the volatilization loss of the organic solvent is greatly reduced;
(4) the technology can adopt pure ethanol as a solvent, is almost nontoxic, cheap and easy to recycle; in addition, the reaction yield is up to more than 80%, the reaction temperature is moderate, and the production control is easy.
(IV) detailed description of the preferred embodiments
The invention will be further described with reference to specific examples for better understanding of the present invention, but the scope of the present invention is not limited thereto.
Example 1: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, and added to a 100ml autoclave, followed by addition of 10ml of methanol; after the oxygen was charged and changed three times, oxygen (pressure 1.8MPa) was introduced and the reaction was carried out in an oil bath at a temperature of 25 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. After the separation by a chromatographic column, 263mg (1.92mmol) of o-nitrotoluene is recovered, the conversion rate of o-nitrotoluene is 68 percent, and 130mg (0.78mmol) of o-nitrobenzoic acid is obtained, and the yield is 13 percent.
Example 2: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, and added to a 100ml autoclave, followed by addition of 10ml of methanol; after the oxygen was charged and changed three times, oxygen (pressure 1.8MPa) was introduced and the reaction was carried out in an oil bath at a temperature of 40 ℃ for 6 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 247mg (1.86mmol) of o-nitrotoluene, wherein the conversion rate of o-nitrotoluene is 69 percent, and obtaining 211mg (1.26mmol) of o-nitrobenzoic acid with the yield of 21 percent.
Example 3: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, and the mixture was put into a 100ml autoclave, 10ml of methanol was added, and after changing oxygen gas three times, oxygen gas (pressure 1.8MPa) was introduced and reacted in an oil bath at a temperature of 40 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 140mg (1.02mmol) of o-nitrotoluene, wherein the conversion rate of the o-nitrotoluene is 83 percent, and obtaining 401mg (2.4mmol) of o-nitrobenzoic acid with the yield of 40 percent.
Example 4: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, and added to a 100ml autoclave, 10ml of methanol was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out in an oil bath at a temperature of 55 ℃ for 12 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 99mg (0.72mmol) of o-nitrotoluene, wherein the conversion rate of the o-nitrotoluene is 88 percent, and obtaining 622mg (3.72mmol) of o-nitrobenzoic acid with the yield of 62 percent.
Example 5: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, and added to a 100ml autoclave, 10ml of methanol was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out in an oil bath at a temperature of 55 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 82mg (0.60mmol) of o-nitrotoluene, wherein the conversion rate of the o-nitrotoluene is 90 percent, and obtaining 672mg (4.02mmol) of o-nitrobenzoic acid with the yield of 67 percent.
Example 6: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, and added to a 100ml autoclave, 10ml of methanol was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out in an oil bath at a temperature of 65 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. After the separation of a chromatographic column, 165mg (1.20mmol) of o-nitrotoluene is recovered, the conversion rate of o-nitrotoluene is 80 percent, and 672mg (4.02mmol) of o-nitrobenzoic acid is obtained, and the yield is 67 percent.
Example 7: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, and added to a 100ml autoclave, 10ml of 50% (V/V) methanol (5 ml of methanol, 5ml of water) was added, after changing oxygen three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out for 24 hours in an oil bath at a temperature of 65 ℃. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 420mg (3.06mmol) of o-nitrotoluene, wherein the conversion rate of the o-nitrotoluene is 49 percent, and obtaining 331mg (1.98mmol) of o-nitrobenzoic acid with the yield of 33 percent.
Example 8: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, and added to a 100ml autoclave, 10ml of 80% (V/V) methanol (8 ml of methanol, 2ml of water) was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out in an oil bath at 55 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. After separation by a chromatographic column, 222mg (1.62mmol) of o-nitrotoluene was recovered, the conversion rate of o-nitrotoluene was 73%, and 572mg (3.42mmol) of o-nitrobenzoic acid was obtained in a yield of 57%.
Example 9: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, added to a 100ml autoclave, 10ml of absolute ethanol was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out in an oil bath at a temperature of 55 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. After separation by a chromatographic column, 165mg (1.2mmol) of o-nitrotoluene was recovered, the conversion rate of o-nitrotoluene was 80%, and 712mg (4.26mmol) of o-nitrobenzoic acid was obtained with a yield of 71%.
Example 10: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, added to a 100ml autoclave, 10ml of ethanol was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out in an oil bath at a temperature of 65 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by chromatography column, recovering 74mg (0.54mmol) of o-nitrotoluene, and obtaining 762mg (4.56mmol) of o-nitrobenzoic acid with the yield of 76% and the conversion rate of o-nitrotoluene of 91%.
Example 11: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, added to a 100ml autoclave, 10ml of ethanol was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out in an oil bath at a temperature of 75 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 82mg (0.60mmol) of o-nitrotoluene, wherein the conversion rate of the o-nitrotoluene is 90 percent, and obtaining 712mg (4.26mmol) of o-nitrobenzoic acid with the yield of 71 percent.
Example 12: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, added to a 100ml autoclave, 10ml of ethanol was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out in an oil bath at a temperature of 85 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 107mg (0.78mmol) of o-nitrotoluene, wherein the conversion rate of the o-nitrotoluene is 87 percent, and obtaining 672mg (4.02mmol) of o-nitrobenzoic acid with the yield of 67 percent.
Example 13: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.6g, 40mmol) were taken, added to a 100ml autoclave, 10ml of ethanol was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out in an oil bath at a temperature of 55 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 247mg (1.80mmol) of o-nitrotoluene, wherein the conversion rate of o-nitrotoluene is 70 percent, and obtaining 391mg (2.34mmol) of o-nitrobenzoic acid with the yield of 39 percent.
Example 14: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (2.0g, 50mmol) were taken, added to a 100ml autoclave, 10ml of ethanol was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out in an oil bath at a temperature of 55 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 140mg (1.02mmol) of o-nitrotoluene, wherein the conversion rate of the o-nitrotoluene is 83 percent, and obtaining 421mg (2.52mmol) of o-nitrobenzoic acid with the yield of 42 percent.
Example 15: taking o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol), adding into a 100ml autoclave, and adding 10ml of 50% (V/V) ethanol (5 ml of ethanol, 5ml of water); after the oxygen was charged and changed three times, oxygen (pressure 1.8MPa) was introduced and the reaction was carried out in an oil bath at a temperature of 65 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. After separation by a chromatographic column, 304mg (2.22mmol) of o-nitrotoluene is recovered, the conversion rate of o-nitrotoluene is 63%, and 381mg (2.28mmol) of o-nitrobenzoic acid is obtained, and the yield is 38%.
Example 16: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, added to a 100ml autoclave, 10ml of 80% (V/V) ethanol (8 ml of ethanol, 2ml of water) was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out for 24 hours in an oil bath at a temperature of 55 ℃. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. After separation by a chromatographic column, 107mg (0.78mmol) of o-nitrotoluene was recovered, the conversion rate of o-nitrotoluene was 87%, and 692mg (4.14mmol) of o-nitrobenzoic acid was obtained, with a yield of 69%.
Example 17: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, added to a 100ml autoclave, 10ml of 80% (V/V) ethanol (8 ml of ethanol, 2ml of water) was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out for 36 hours in an oil bath at a temperature of 55 ℃. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 132mg (0.96mmol) of o-nitrotoluene, wherein the conversion rate of the o-nitrotoluene is 84 percent, and obtaining 752mg (4.5mmol) of o-nitrobenzoic acid with the yield of 75 percent.
Example 18: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, added to a 100ml autoclave, 10ml of 80% (V/V) ethanol (8 ml of ethanol, 2ml of water) was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out for 48 hours in an oil bath at a temperature of 55 ℃. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 82mg (0.6mmol) of o-nitrotoluene, wherein the conversion rate of the o-nitrotoluene is 90 percent, and obtaining 802mg (4.8mmol) of o-nitrobenzoic acid with the yield of 80 percent.
Example 19: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, added to a 100ml autoclave, 10ml of 80% (V/V) ethanol (8 ml of ethanol, 2ml of water) was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out for 72 hours in an oil bath at a temperature of 55 ℃. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 58mg (0.42mmol) of o-nitrotoluene, and obtaining 832mg (4.98mmol) of o-nitrobenzoic acid with the yield of 83 percent, wherein the conversion rate of the o-nitrotoluene is 93 percent.
Example 20: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, and added to a 100ml autoclave, 10ml of 80% (V/V) ethanol (8 ml of ethanol, 2ml of water) was added, and reacted in air under an oil bath at a temperature of 55 ℃. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. After the separation of a chromatographic column, 592mg (4.32mmol) of o-nitrotoluene is recovered, the conversion rate of o-nitrotoluene is 28 percent, 70mg (0.42mmol) of o-nitrobenzoic acid is obtained, and the yield is 7 percent.
Example 21: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, placed in a 100ml autoclave, 10ml of isopropanol was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and the reaction was carried out in an oil bath at a temperature of 55 ℃ for 24 hours. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. Separating by a chromatographic column, recovering 82mg (0.60mmol) of o-nitrotoluene, wherein the conversion rate of the o-nitrotoluene is 90 percent, and obtaining 722mg (4.32mmol) of o-nitrobenzoic acid with the yield of 72 percent.
Example 22: o-nitrotoluene (823mg, 6mmol) and sodium hydroxide (1.8g, 45mmol) were taken, added to a 100ml autoclave, 10ml of 80% (V/V) isopropanol (8 ml of isopropanol, 2ml of water) was added, oxygen was charged three times, oxygen (pressure 1.8MPa) was introduced, and reaction was carried out for 24 hours in an oil bath at a temperature of 55 ℃. Diluting with methanol after reaction, neutralizing reaction mixture to pH 2-3, removing most solvent under reduced pressure, adding ethyl acetate, drying, and filtering. After the separation of a chromatographic column, 263mg (1.92mmol) of o-nitrotoluene is recovered, the conversion rate of the o-nitrotoluene is 68 percent, and 602mg (3.6mmol) of o-nitrobenzoic acid is obtained, and the yield is 60 percent.
Claims (5)
1. A method for preparing o-nitrobenzoic acid by oxidizing o-nitrotoluene without catalyst oxygen is characterized by comprising the following steps: under the condition of not adding any catalyst, taking o-nitrotoluene as a raw material, taking oxygen as an oxidant and sodium hydroxide as alkali, reacting for 24-72 hours in a solvent at a certain reaction temperature, and separating and purifying to obtain o-nitrobenzoic acid; the concentration of the raw material o-nitrotoluene is 0.3-3.0 mol/L; the concentration of the sodium hydroxide is 4.5-5.0 mol/L; the oxygen pressure is 1.8-2.0MPa, and the neutralization reaction liquid is carried out after the reaction until the pH value is 1-7;
in particular, when ethanol is used as a solvent, the reaction temperature is 55-85 ℃;
when 80% ethanol aqueous solution was used as the solvent, the reaction temperature was 55 ℃.
2. The process for preparing o-nitrobenzoic acid by the oxidation of o-nitrotoluene with oxygen in the absence of a catalyst according to claim 1, wherein: the concentration of the raw material o-nitrotoluene is 0.5-2.0 mol/L.
3. The process for preparing o-nitrobenzoic acid by the oxidation of o-nitrotoluene with oxygen in the absence of a catalyst according to claim 1, wherein: the concentration of the raw material o-nitrotoluene is 0.5-0.6 mol/L.
4. The process for preparing o-nitrobenzoic acid by the oxidation of o-nitrotoluene with oxygen in the absence of a catalyst according to claim 1, wherein: after the reaction, the reaction solution is neutralized to a pH value of 2-4.
5. The process for preparing o-nitrobenzoic acid by the oxidation of o-nitrotoluene with oxygen in the absence of a catalyst according to claim 1, wherein: the method comprises the following specific steps: adding o-nitrotoluene and sodium hydroxide into a high-pressure kettle, and adding a solvent; introducing oxygen after multiple times of oxygen exchange, controlling the temperature to react, adding a solvent to dilute after the reaction, neutralizing the pH value of the reaction mixed solution, removing the solvent under reduced pressure, adding ethyl acetate, drying, filtering, and separating by a chromatographic column.
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| 硝基甲苯的液相催化氧化研究;李志刚;《中国优秀博硕士学位论文全文数据库（硕士）工程科技I辑》;20021215;第B014-13页 * |
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