CN116003292A - A kind of method of synthesizing amino azobenzene - Google Patents

Abstract

The invention relates to the synthesis of compounds, in particular to a method for synthesizing aminoazobenzene. Use substituted aniline as raw material, use alcohol as solvent, and synthesize aminoazobenzene through diazo and coupling (self-coupling or coupling with other aniline substances). The coupling reaction is to mix methanol and substituted aniline (coupling component), adjust the pH of the system to 5-6, control the temperature of the system to 0-100, and add diazo solution dropwise to the system at ℃, and adjust the pH of the system to be between 4-6 at this time. During the period, after the dropwise addition of the diazo solution, continue to incubate for 1.5-2h, during which the pH=4-6 is maintained; after the reaction is completed, the pH is adjusted to 6.5-7, and the aminoazobenzene is obtained by filtration. The synthesis of aminoazobenzene of the present invention takes m-toluidine (or o-methylaniline) as a raw material, uses alcohol as a solvent, and synthesizes 4-aminoazobenzene through diazo coupling (self-coupling or coupling with other aniline substances) At the same time, the pH value of the reaction is controlled during the reaction process, so that the reaction recovery is convenient, and at the same time, the solubility of the raw materials can be improved, the reaction is easier to carry out, and the counter cycle is greatly shortened.

Description

A kind of method of synthesizing amino azobenzene

technical field

The invention relates to the synthesis of compounds, in particular to a method for synthesizing aminoazobenzene.

Background technique

Aminoazobenzene itself is a commonly used dye, which can be used as an intermediate for other dyeing pigments, such as p-aminoazobenzene (aniline yellow), which is prepared by aniline diazotization self-coupling, and is used to make azo dyes and Oxazine dyes, etc. (acid red GR disperse yellow RGFL); can also be used for acid-base indication, such as p-dimethylamino azobenzene, which can be used as an acid-base indicator, pH2.9 (red) ~ 4.0 (yellow), Determination of free hydrochloric acid in gastric juice, spot test of peroxidized fat; used as acid-base indicator, indicator for non-aqueous titration and determination of free hydrochloric acid in gastric juice; also used in the synthesis of other substituted amine compounds, such as 2,5 -Diaminotoluene is obtained by reducing the self-coupling product of o-aminotoluene.

The main synthesis method of aminoazobenzene compounds is the diazo coupling method. The existing method mainly uses water as the solvent and sodium nitrite as the diazotization reagent.

Patent CN101450904A reports that the intermediate 2-aminoazotoluene (C.I.11160) is obtained after coupling 2-aminotoluene with diazo in the water phase, and the azo compound is obtained by filtration with a yield of 92.44%.

The current industrialization mostly adopts this method for production, and the process condition is to react in an aqueous phase system. In order to ensure the dispersion effect, a large amount of water needs to be used in the reaction process, resulting in a large amount of waste water, serious environmental pollution, and difficult post-treatment. Under this process condition, restricted by the nature of the reaction raw material, the reaction cycle is long, and the time for adding sodium nitrite to the water needs to be more than 5 hours. If the addition is too fast, it will easily cause the accumulation of reaction heat. The specific heat capacity of the diazo coupling reaction material and liquid is about 3.2kJ· kg ^-1 ·K ^-1 , the diazo coupling reaction process is exothermic, with an apparent heat release of 651.4kJ kg ^-1 (based on the mass of m-toluidine), and an adiabatic temperature rise of about 50.0K. Substituted aniline The stability of diazonium salt is poor, and the risk of loss of control in the process is relatively high.

In the new synthesis method of p-diaminoazobenzene published in the Journal of Neijiang Normal University 2010 (25, 117-118), Zhang Fengchun and others introduced the use of p-nitroaniline as raw material, and the reduction of lead, zinc and glucose respectively. Reagent, method for synthesizing 4,4'-diaminoazobenzene (azoaniline).

Although this method is clean and environmentally friendly, the yield is too low to be suitable for industrial production.

Contents of the invention

The purpose of the present invention is to provide a method for synthesizing aminoazobenzene.

In order to achieve the above object, the technical solution adopted by the present invention is:

A method for synthesizing aminoazobenzene uses substituted aniline as a raw material, uses alcohol as a solvent, and synthesizes aminoazobenzene through diazo and coupling (self-coupling or coupling with other aniline substances) reactions.

The coupling reaction is to mix methanol and substituted aniline (coupling component), adjust the pH of the system to 5-6, control the temperature of the system at 0-100°C, and add diazo liquid dropwise into the system, and adjust the pH of the system to be between 4-6. During the period, after the diazo solution is added dropwise, continue to incubate for 1.5-2h, during which the pH=4-6 is maintained; after the reaction, adjust the pH=6.5-7, and filter to obtain aminoazobenzene; wherein, in the coupling component The substituted aniline can be the same or different from the raw material substituted aniline obtained in the diazo solution.

Said use substituted aniline as raw material (diazo component), use alcohol as solvent, add hydrochloric acid dropwise at room temperature, stir and mix evenly, make the pH in the system <1, and obtain substituted aniline hydrochloride alcohol solution for use; then add substituent Sodium nitrate aqueous solution, carry out diazonium reaction, obtain diazonium liquid;

Then a continuous tubular reactor is used, the temperature is set at 0-5°C, and the substituted aniline hydrochloride methanol solution and sodium nitrite aqueous solution are added to the reactor at the same time in proportion to the residence time of 10-60s to obtain the diazonium solution. Dropwise added to the coupling tank for coupling reaction.

Above-mentioned diazonium reaction system:

wherein R ₁ , R ₂ , R ₃ , and R ₄ are identical or different and are selected from H or C _1-4 alkyl groups; wherein, R ₁ and/or R ₂ on the benzene ring form an ortho or meta position with the amino group, respectively;

Use sodium nitrite aqueous solution as the diazotization reagent, substituted aniline (diazo component): sodium nitrite: hydrochloric acid: substituted aniline (coupling component) = 1.0:1.0-1.2:2.0-2.5:1.0 (mol ratio).

The alcohol is a C _1-4 primary alcohol, preferably methanol, ethanol or the like.

During the coupling step, the temperature is 10-30° C., and the pH is controlled at 4.0-5.0.

When the alcohol and the substituted aniline (coupling component) are mixed, the pH of the system is adjusted by hydrochloric acid, and the pH of the system is adjusted by alkali after the diazo component is added.

The base is an inorganic base; for example, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, and the like.

The advantages that the present invention has:

The synthesis of aminoazobenzene of the present invention takes m-toluidine (or o-methylaniline) as a raw material, uses alcohol as a solvent, and synthesizes 4-aminoazobenzene through diazo coupling (self-coupling or coupling with other aniline substances) reaction. At the same time, the pH value of the reaction is controlled during the reaction process, so that the reaction recovery is convenient, the amount of three wastes is less, and the solubility of the raw materials can be improved at the same time, so that the reaction is easier to carry out, and the counter cycle is greatly shortened; specifically:

1) The present invention solves the problem of the solubility of raw materials by using alcohol solvents, even under relatively high pH conditions, it can also ensure that the substituted anilines are dissolved in the reaction system, greatly improving the coupling reaction speed;

2) Control the coupling pH condition of the present invention to be 4-6, and the reaction time is less than 2h, which greatly shortens the reaction time of the water phase under the same conditions as the prior art (greater than 8h). Not only that, the use of alcohol solvent system can improve the stability of diazonium salt and effectively inhibit the occurrence of side reactions of hydrolysis.

Detailed ways

The specific embodiments of the present invention will be further described below in conjunction with examples. It should be noted that the specific embodiments described here are only for illustrating and explaining the present invention, and are not intended to limit the present invention.

In the existing preparation of aminoazobenzene, during the synthesis process of aminoazobenzene, the pH value of the system has a great influence on the reactions of each step. According to the diazotization reaction mechanism, the higher the acid concentration, the larger the dosage, the faster the reaction speed and the more stable the product.

According to the mechanism of the coupling reaction, weakly acidic or even alkaline conditions are required. The main coupling compound in this study is substituted aniline, and the optimum pH value for coupling is 4-7.

Under the condition of water phase, the substituted aniline needs to be made into hydrochloride to be dissolved, and its hydrochloride has a strong acidity, which makes it difficult for the coupling reaction to occur, and the system is adjusted to the required weak acidic condition to replace the aniline The solubility of the diazonium salt is very low, which leads to a very slow coupling reaction speed, and the stability of the diazonium salt is very poor under acidic conditions. The two conditions restrict each other, resulting in more impurities in the reaction process, affecting product quality and yield. Rate.

Taking m-methylaniline as an example, its coupling products mainly include the following types.

① The main source of impurity-1 is the hydrolysis of diazonium salt, and the by-product phenol is coupled with diazonium salt. Too high system pH, too high temperature, too long reaction time and slow coupling reaction speed will lead to hydrolysis of diazonium salt.

②Impurities-2: Ammonolysis products, usually the pH is too high to increase impurities.

By above-mentioned various defects, the present invention changes the solvent of reaction system to solve existing problems.

Example 1

Add 20ml (16g) of methanol, 10g of hydrochloric acid (36%), and 5.0g of m-toluidine into a 100ml reaction flask, cool down to 0-5°C, and set aside.

Take 3.25g of sodium nitrite and 6g of water to prepare a solution, add the prepared solution dropwise to the above-mentioned reaction flask, control the temperature at 0-5°C during the dropwise addition, and keep it warm at <5°C for later use. Sampling is controlled in the center, the reaction conversion rate is about 99%, and the purity of the diazonium salt is >98%.

Example 2

Add 50g of methanol and 5.0g of m-toluidine into a 100ml reaction bottle, cool down to below 10°C, add 10g of hydrochloric acid (36%) dropwise to pH ≈ 5, stir until uniform and set aside.

Control the temperature < 10°C and add the diazonium solution in Example 1 dropwise for about 0.5 hours. During this period, the pH value of the system is continuously detected, and the pH value of the system is controlled by sodium hydroxide to 4.0-4.5. After the diazonium salt was added dropwise, it was kept at 8-10°C for 2h.

The control raw material remaining in sampling is less than 3%, and the main product is more than 95%. After passing the central control, adjust the pH to 6.5-7, filter and dry to obtain an orange solid with a yield of 96% and a content of 97%.

Example 3

Prepare m-toluidine methanol solution and sodium nitrite solution according to the ratio in Example 1, and prepare the coupling material primer solution in Example 2 at the same time.

Use a continuous tubular reactor, control the temperature at 0-5°C, add m-toluidine methanol solution and sodium nitrite solution at the same time in proportion, the residence time is 10-15s, and add the production liquid dropwise into the coupling reaction bottle, the control conditions are the same as the example 2. Yield 96.5%, content 97%.

Example 4

Add 20ml (16g) of methanol, 10g of hydrochloric acid (36%), and 5.0g of o-toluidine into a 100ml reaction flask, cool down to 0-5°C, and set aside.

Take 3.25g of sodium nitrite and 6g of water to prepare a solution, add the prepared solution dropwise to the above-mentioned reaction flask, control the temperature at 0-5°C during the dropwise addition, and keep it warm at <5°C for later use. Sampling is controlled in the center, the reaction conversion rate is about 99%, and the purity of the diazonium salt is >98%.

Example 5

Add 50g of methanol and 5.0g of o-toluidine into a 100ml reaction bottle, cool down to below 10°C, add 10g of hydrochloric acid (36%) dropwise to pH ≈ 5, stir until uniform and set aside.

Control the temperature < 10°C and add the diazonium solution in Example 1 dropwise for about 0.5 hours. During this period, the pH value of the system is continuously detected, and the pH value of the system is controlled by sodium hydroxide to 4.0-4.5. After the diazonium salt was added dropwise, it was kept at 8-10°C for 2h.

The control raw material remaining in sampling is less than 3%, and the main product is more than 95%. After passing the central control, adjust the pH to 6.5-7, filter and dry to obtain an orange solid with a yield of 93.9% and a content of 97%.

Example 6

Use a continuous tubular reactor, control the temperature at 0-5°C, add o-toluidine methanol solution and sodium nitrite solution at the same time in proportion, the residence time is 10-15s, and add the production liquid dropwise into the coupling reaction bottle, the control conditions are the same as the example 5. Yield 94.8%, content 97%.

Claims (8)

1. A method for synthesizing aminoazobenzene, characterized in that: take substituted aniline as raw material, use alcohol as solvent, react synthetic aminoazo through diazo, coupling (self-coupling or coupling with other aniline substances) benzene. 2. by the method for the described synthetic aminoazobenzene of claim 1, it is characterized in that: described coupling reaction is that methyl alcohol and substituted aniline (coupling component) mix, adjust system pH=5～6, control system temperature 0 -100°C, add diazo solution dropwise to the system, at this time, adjust the pH of the system to be between 4-6, after the diazo solution is added dropwise, continue to keep warm for 1.5-2h, during which pH=4-6 is maintained; after the reaction, Adjust the pH to 6.5-7, and filter to obtain aminoazobenzene; wherein, the substituted aniline in the coupling component and the raw material substituted aniline in the obtained diazo solution may be the same or different. 3. by the method for the described synthetic aminoazobenzene of claim 2, it is characterized in that: described take substituted aniline as raw material (diazo component), use alcohol to make solvent, drip hydrochloric acid under room temperature, stir and mix , so that the pH in the system is less than 1, and the substituted aniline hydrochloride alcohol solution is obtained for use; then an aqueous solution of sodium nitrite is added to carry out a diazo reaction to obtain a diazo solution; Then a continuous tubular reactor is used, the temperature is set at 0-5°C, and the substituted aniline hydrochloride methanol solution and sodium nitrite aqueous solution are added to the reactor at the same time in proportion to the residence time of 10-60s to obtain the diazonium solution. Dropwise added to the coupling tank for coupling reaction. 4. by the method for the synthetic aminoazobenzene described in any one of claim 1-3, it is characterized in that: reaction system:

wherein R ₁ , R ₂ , R ₃ , and R ₄ are identical or different and are selected from H or C _1-4 alkyl groups; wherein, R ₁ and/or R ₂ on the benzene ring form an ortho or meta position with the amino group, respectively; Use sodium nitrite aqueous solution as the diazotization reagent, substituted aniline (diazo component): sodium nitrite: hydrochloric acid: substituted aniline (coupling component) = 1.0:1.0-1.2:2.0-2.5:1.0 (mol ratio). 5. by the method for the synthetic aminoazobenzene described in any one of claim 1-3, it is characterized in that: described alcohol is the primary alcohol that is C _1-4 . 6. The method for synthesizing aminoazobenzene according to claim 2, characterized in that: the temperature in the coupling step is 10-30° C., and the pH is controlled at 4.0-5.0. 7. by the method for the described synthetic aminoazobenzene of claim 2, it is characterized in that: adopt hydrochloric acid to regulate system pH when described alcohol and substituted aniline (coupling component) mix, adopt alkali to regulate system after adding diazo component pH. 8. by the method for the described synthetic aminoazobenzene of claim 7, it is characterized in that: described alkali is inorganic base.