Method for prolonging service life of free radical and maintaining reaction activity of free radical by using inert gas and application

Abstract

The invention discloses a method for prolonging the service life of common free radicals and maintaining the chemical reaction activity of the free radicals by injecting or dissolving inert gas into a reaction system. The inert gas-free radical intermediate formed by inert gas molecules or atoms and free radicals prolongs the service life of the free radicals, and meanwhile, the high chemical activity of the free radicals in the inert gas-free radical intermediate is ensured by utilizing a full stable electronic structure of the inert gas, so that the reaction rate of multiphase and homogeneous reaction is effectively improved. According to the method disclosed by the invention, the selectivity or free radical reaction activity control of multiphase and homogeneous free radical reactions can be realized without introducing common free radical stabilizers (such as allyl, benzyl acetyl, aminomethyl and the like), and the inert gas has the characteristics of reusability and no toxicity; the method is suitable for free radical reactions requiring cyclic utilization of the stabilizer and free radical reactions requiring non-toxicity of the stabilizer.

Description

Technical Field

[0001] The invention belongs to the field of chemistry and relates to a method and application of utilizing inert gas to prolong the life of free radicals and maintain the reaction activity of free radicals. Background Art

[0002] Free radicals are atoms or groups with unpaired electrons. Since unpaired electrons often have very high chemical reactivity, free radicals are initiators of many important chemical reactions. For organic reactions, free radical reactions are one of the three basic reactions. In organisms, free radicals can often alkylate protein side chains, thereby causing pathological changes. Studying the relationship between free radicals and diseases is a cutting-edge topic in the medical field.

[0003] The importance of free radicals comes from their unique structure and properties. The most notable characteristics of free radicals are: 1. High chemical activity; 2. Short life and easy quenching. Maintaining high activity while extending the life of free radicals is a long-standing unsolved problem in the field of free radical research. At present, a common method to extend the life of free radicals is to use electron-rich materials to stabilize the unpaired electrons in free radicals. Commonly used electron-rich materials include: benzene rings and ferrocene derivatives. However, these electron-rich materials are mostly aromatic hydrocarbon systems, which increase toxicity. At the same time, the aromatic hydrocarbons in the above-mentioned electron-rich materials are chemically unstable and prone to substitution reactions. Due to these characteristics, the method of using electron-rich materials to stabilize free radicals is not suitable for cyclic free radical reactions and free radical reactions that require non-toxic reactions.

[0004] Because of their saturated electronic structure, noble gases have stable chemical properties. Therefore, it is difficult for noble gases to form bonds with other elements to form stable compounds. However, some noble gases (such as Xe) have huge, polarizable electron clouds. This property allows noble gases to interact with other atoms by sharing electrons to form some stable structures. For example, Xe gas can complex with solvent molecules in liquid solutions to form a "Xe-solvent molecule" structure. The stronger the polarity of the solvent molecule, the more stable the "Xe-solvent molecule" structure. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the purpose of the present invention is to provide a method and application of using inert gas to prolong the life of free radicals and maintain the reaction activity of free radicals.

[0006] The inert body-free radical intermediate formed by the inert gas atom and the free radical prolongs the free radical life, and the full stable electronic structure of the inert gas is used to ensure the high chemical activity of the free radical in the inert gas-free radical intermediate. The method proposed by the present invention can effectively control and improve the reaction rate and the selectivity of the reaction product in the multiphase and homogeneous reactions in which the free radicals participate by introducing (injecting, dissolving, etc.) an inert gas into the reaction system. The method of the present invention does not need to introduce common free radical stabilizers (such as allyl, benzyl acetyl and aminomethyl, etc.) to achieve the selectivity or free radical reaction activity control of multiphase and homogeneous free radical reactions, and the inert gas has the characteristics of being reusable and non-toxic, and is suitable for free radical reactions that require the recycling of stabilizers and free radical reactions that require the non-toxic stabilizers. Xe gas will form a stable "inert gas-free radical" intermediate with free radicals containing C, H or O, thereby increasing the life of the free radicals.

[0007] The present invention can adopt the following technical solutions:

[0008] Step 1: uniformly mix the material that can generate free radicals under external stimulation and the reactant to form a reaction system; if necessary, a corresponding solvent can be added in the process of forming the reaction system;

[0009] Step 2: Inject or dissolve an inert gas into the above reaction system, and control the amount and / or speed of the inert gas (e.g., 2 mL / min) to extend the life of free radicals, maintain the chemical activity of free radicals, and control the reaction rate of free radical reactions and the selectivity of reaction products. If necessary, free radicals can be induced in the reaction system by external stimuli such as light, electricity, and heat during the above process.

[0010] Compared with the existing free radical stabilization strategy, the present invention utilizes chemically stable and non-toxic inert gas as a free radical stabilizer, and is suitable for free radical reactions that require the recycling of stabilizers and free radical reactions that require non-toxic stabilizers.

[0011] The inert gas used in the present invention includes Xe gas (including isotope Xe 132 、Xe 131 、Xe 129 、Xe 134 、Xe 136 、Xe 130 、Xe 128 and Xe 124 etc.), Kr gas, Ar gas, Ne gas, He gas, N 2 Gas; preferably, comprising Xe gas.

[0012] In step 1, the material that can generate free radicals through external stimulation includes but is not limited to solid catalysts, liquid catalysts, etc.; wherein the solid catalyst includes metal-supported semiconductor materials, metal catalysts, and semiconductor materials; the liquid catalyst includes organic or inorganic solvents that are easy to decompose free radicals, the inorganic solvent includes aqueous hydrogen peroxide solution, etc., the organic solvent includes ZIF-4, Im-UiO-PL, etc.; the metal-supported semiconductor catalyst includes Pt / C 3 N 4 、Pd / C 3 N 4 、Pd / TiO 2 , co-catalyst / semiconductor photocatalyst, etc.; the metal catalyst includes metal catalysts such as Pd, Pt, Fe, etc.; the semiconductor catalyst includes TiO 2 , CdS, etc.;

[0013] Specifically, the material that can generate free radicals by external stimulation includes Pt / C 3 N 4 、Pd / C 3 N 4 、Pd / TiO 2 、Pd、Pt、Fe、TiO 2 , CdS, H 2 O 2 One or more of aqueous solution, ZIF-4, Im-UiO-PL, etc., preferably, Pt / C 3 N 4 , H 2 O 2 aqueous solution; the catalyst is powder or liquid, the addition amount is 0.2mg~5mg, the H 2 O 2 The concentration (volume fraction) of the aqueous solution is 5% to 80%; preferably, the amount of the catalyst added is 2 mg, H 2 O 2 The concentration (volume fraction) of the aqueous solution is 30%.

[0014] In step 1, one or more of methanol, ethanol, water, dimethyl sulfoxide, chloroform, etc. can be selected as the reaction solvent; preferably, a mixed solution of methanol and water is used as the reaction solvent. The operation process of step 1 needs to be protected from light and oxygen to avoid external stimulation that causes premature release and quenching of free radicals. The operation process and requirements are well known in the industry.

[0015] In step 2, a sealed container can be used to solve the problem of inert gas escape under a certain pressure, and the pressure is 1 to 5 bar. If the inert gas has a high solubility in a specific solvent, a sealed container may not be required. Preferably, a sealed container is selected and the inert gas is injected into the reaction system at a pressure of 3 bar.

[0016] In step 1, the reactants may be reduced glutathione, methyl orange, rhodamine B, methanol, etc. Preferably, they are reduced glutathione and methanol.

[0017] In step 2, free radicals can be induced in the reaction system by external stimuli such as light, electricity, and heat. In the case of inducing free radicals by light, one or more of ordinary xenon lamp light sources, mercury lamp light sources, metal halide lamp light sources, laser light sources, etc. can be used to induce the generation of free radicals in the reaction system. In the electrically induced free radical system, an external electrochemical workstation or power supply is used to induce free radicals; in the thermally induced free radical system, the temperature range can be 25°C to 400°C; preferably, 60°C.

[0018] The present invention provides a method for extending the life of free radicals and maintaining the chemical activity of free radicals by using inert gas. The method proposed by the present invention can not only effectively increase the reaction rate in multiphase and homogeneous reactions involving free radicals, but also realize the control of the selectivity of reaction products.

[0019] The present invention also provides an inert gas-free radical intermediate, wherein the inert gas-free radical intermediate is a free radical intermediate containing C, H or O.

[0020] The present invention also provides the above method, or the above inert gas-free radical intermediate, which prolongs the life of free radicals and maintains the chemical activity of free radicals, so that it can be used in the fields of medicine (for example: detection of highly reactive oxygen species), energy chemistry (for example: selective preparation of carbon dioxide reduction reaction products), and environment (for example: the effect of highly reactive oxygen groups on the degradation of pollutants).

[0021] Compared with the prior art, the beneficial effects of the present invention include:

[0022] (1) Inert gases can form an "inert gas-free radical" structure with free radicals under mild conditions (room temperature, normal pressure or lower pressure). The formation of this structure can prolong the life of free radicals while ensuring the high chemical activity of free radicals.

[0023] (2) The "inert gas-free radical" structure can effectively increase the reaction rate in heterogeneous and homogeneous reactions involving free radicals and achieve the control of the selectivity of the reaction products. Xe gas will form a stable "inert gas-free radical" intermediate with free radicals containing C, H or O, thereby increasing the lifetime of the free radical.

[0024] (3) As a free radical stabilizer, inert gas has the advantages of stable structure and non-toxicity, and is suitable for free radical reactions that require the recycling of stabilizers and free radical reactions that require the stabilizers to be non-toxic. It can prolong the life of free radicals, thereby increasing the detection time of free radicals or increasing the yield of reactions involving free radicals. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 In Example 1 of the present invention, Xe gas and N 2 Paramagnetic resonance spectra under ventilation and non-ventilation conditions.

[0027] Figure 2 : Spin density distribution diagram of four free radicals and Xe.

[0028] Figure 3 In Example 1 of the present invention, Xe gas (above) and N are injected into the reaction system. 2 After the gas (below) 1 H NMR spectrum. The reaction system used is the reaction system of GSH and hydroxyl radicals.

[0029] Figure 4 : Paramagnetic resonance spectra of the reaction system with and without Xe gas injection (gray line) in Example 2 of the present invention.

[0030] Figure 5 : In Example 2 of the present invention, the reaction system was not injected with Xe gas and was injected with Xe gas. 1 H NMR spectrum. The reaction system used was Pt / C 3 N 4 A methanol and water mixture reaction system with a catalyst.

[0031] Figure 6 : In Example 2 of the present invention, after stopping the illumination, CH 3 Changes in the concentration of O· free radicals. DETAILED DESCRIPTION

[0032] The present invention is further described in detail with reference to the following specific examples and drawings. The process, conditions, experimental methods, etc. for implementing the present invention, except for the contents specifically mentioned below, are all common knowledge and common common sense in the art and are not particularly limited by the present invention.

[0033] The present invention provides a method for extending the life of common free radicals and maintaining the chemical reactivity of free radicals by injecting or dissolving an inert gas (e.g., Xe gas) into a reaction system. The present invention extends the life of free radicals through an inert gas (e.g., Xe gas)-free radical intermediate formed by an inert gas molecule or atom (e.g., Xe atom) and a free radical, and at the same time, utilizes the fully stable electronic structure of the inert gas (e.g., Xe gas) to ensure the high chemical activity of the free radicals in the inert gas (e.g., Xe gas)-free radical intermediate, thereby effectively improving the reaction rate of multiphase and homogeneous reactions. The method of the present invention does not need to introduce a common free radical stabilizer (e.g., allyl, benzyl acetyl, and aminomethyl, etc.) to achieve the selectivity of multiphase and homogeneous free radical reactions or free radical reaction activity control, and the inert gas (e.g., Xe gas) has the characteristics of being reusable and non-toxic, and is suitable for free radical reactions that require the recycling of stabilizers and free radical reactions that require the stabilizer to be non-toxic.

[0034] Example 1: Xe gas enhances the activity of hydroxyl radicals and then oxidizes and reduces glutathione (GSH)

[0035] Step 1: Preparation of reduced glutathione (GSH) reaction solution

[0036] 500ul D 2 O+5mg GSH+5ul H 2 O 2 (30% aqueous solution)

[0037] GSH can combine with OH free radicals to reduce OH free radicals to H 2 O. Hydrogen peroxide can be cleaved into OH free radicals under ultraviolet light (320nm~380nm).

[0038] Step 2: Observe the free radicals in the system using paramagnetic resonance

[0039] Hydroxyl radicals can be detected using paramagnetic resonance. Figure 1 In order to inject xenon gas and N 2 The paramagnetic resonance spectra of the reaction system with and without gas. The 6 peaks in the figure are the paramagnetic resonance signals of hydroxyl radicals. 2 The paramagnetic resonance signal of hydroxyl radicals was significantly enhanced, with Xe gas being the strongest.

[0040] In order to study the interaction between Xe and free radicals, the M062X / Def2QZVPP method was used to perform geometric optimization of the interaction configuration between free radicals and Xe. Figure 2It can be seen that the stability of the combination of Xe and free radicals. By analyzing the spin density distribution, it can be clearly seen that the lone pair of electrons on the free radical is transferred to Xe. This electron transfer indicates that there is a weak bond interaction between Xe and the free radical, thus forming a stable interaction configuration between Xe and the free radical.

[0041] Step 3: NMR observation of the oxidation process of reduced glutathione

[0042] Nuclear magnetic resonance 1 H spectrum observation of the process of hydroxyl radical oxidation and reduction of glutathione. Figure 3 Inject xenon gas ( Figure 3 on) and injected N 2 gas( Figure 3 Next) 1 H NMR spectrum. It can be seen that after the reaction system was injected with xenon gas, the yield of products in which hydroxyl radicals participated in the reaction increased significantly.

[0043] It can be found from Example 1 that the injection of xenon gas into the reduced glutathione reaction solution can greatly promote the life of *OH free radicals, thereby enhancing the oxidation reaction of reduced glutathione.

[0044] Example 2: Xe gas enhances the activity of methoxy radicals and selectively enhances the formation of the reaction product methyl formate

[0045] Step 1: Preparation of catalyst

[0046] Pt / C was prepared by coprecipitation method. 3 N 4 Catalyst. 3 N 4 (200 mg) powder and add appropriate amount of H 2 PtCl 6 The aqueous solution was kept at 80 °C for 1 h. After drying, the product was calcined at 180 °C for 1 h to obtain the final catalyst Pt / C 3 N 4 .

[0047] Step 2: Xenon lamp radiation cracking of methanol to produce methoxyl radicals

[0048] 2 mg of catalyst was evenly dispersed in 450 ul CD 3 OD and 50ul CH 3 OH mixed solution, the mixed solution was ultrasonically treated for 0.5h in the dark to make the catalyst evenly dispersed in the solution and to expel the dissolved air in the solution. The above suspension was transferred to a closed gas storage nuclear magnetic tube in a vacuum glove box, and then 3bar Xe gas was injected and shaken thoroughly.

[0049] The sealed NMR tube after Xe gas is fully dissolved is placed under a 300W xenon lamp for photocatalytic experiment. After the optical fiber is illuminated, polar methoxyl radicals and subsequent methanol reforming products will continue to be produced in the NMR tube. Figure 4 As shown in the figure, clear CH 3 O· free radical (AN = 14.37 Gauss, AH = 2.93 Gauss). However, in the system injected with Xe gas, CH 3 The signal intensity of O· free radicals is significantly greater than that of CH in the system without Xe gas injection (No gas). 3 The signal intensity of O· free radicals indicates that the presence of Xe gas prolongs the free radical lifetime, thereby increasing the free radical concentration in the reaction system.

[0050] Step 3: NMR observation of free radical reaction products

[0051] The photoreaction products of the above system are methyl formate (MF), acetal (DMM) and hemiacetal (MM). By comparing the NMR of the system with and without Xe gas injection, the 1 H spectrum showed that the yield of methyl formate in the reaction system injected with Xe gas increased significantly compared with the reaction system without Xe gas. However, the yields of acetal and hemiacetal were almost unchanged. 3 O· is produced by free radical reaction, while hemiacetal and acetal are produced by non-free radical reaction between HCHO intermediate and methanol molecule (acetal reaction). Figure 5 The spectrum shows that Xe gas extends CH 3 After O·life, CH 3 O· related free radical reactions significantly increased the yield of methyl formate in the reaction, while the yield of non-free radical reaction products in the reaction system was almost unaffected. Figure 6 As shown in the figure, when the light is turned off in the Xe gas system, the free radicals can still survive for more than 10 minutes.

[0052] The protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the present invention, changes and advantages that can be thought of by those skilled in the art are included in the present invention and are protected by the attached claims.

Claims

1. A method for extending the life of free radicals and maintaining the reactivity of free radicals using inert gas, It is characterized in that The method comprises the following steps: Step 1: uniformly mix the material that can generate free radicals through external stimulation and the reactant to form a reaction system; Step 2: inject or dissolve an inert gas into the reaction system in step 1, and control the introduction rate and / or amount of the inert gas to extend the life of the free radicals, maintain the chemical activity of the free radicals, and control the reaction rate of the free radical reaction and the selectivity of the reaction products.

2. The method according to claim 1, It is characterized in that The inert gas includes Xe gas, Kr gas, Ar gas, Ne gas, He gas, N 2 gas.

3. The method according to claim 1, It is characterized in that In step 1, the material that can generate free radicals through external stimulation includes a solid catalyst and a liquid catalyst; wherein the solid catalyst includes a metal-loaded semiconductor material, a metal catalyst, and a semiconductor material; the liquid catalyst is an organic or inorganic solvent that can easily decompose free radicals; and the reactants include reduced glutathione, methyl orange, rhodanine b, and methanol.

4. The method according to claim 3, It is characterized in that The metal-supported semiconductor material includes Pt / C 3 N 4 、Pd / C 3 N 4 、Pd / TiO 2 , co-catalyst / semiconductor photocatalyst; the metal catalyst includes Pt, Pd, Fe; the semiconductor catalyst includes TiO 2 , CdS; the inorganic solvent that is easy to decompose free radicals includes aqueous hydrogen peroxide solution, and the organic solvent that is easy to decompose free radicals includes ZIF-4 and Im-UiO-PL; the added amount of the catalyst is 0.2 to 5 mg.

5. The method according to claim 1, It is characterized in that In step 1, the reaction system further includes a solvent, and the solvent includes methanol, ethanol, water, dimethyl sulfoxide, and chloroform.

6. The method according to claim 1, It is characterized in that In step 2, the injection pressure of the inert gas is 1 to 5 bar.

7. The method according to claim 1, It is characterized in that In step 2, the external stimulus for inducing free radicals in the reaction system includes light, electricity, and heat; in the light-induced free radical system, the external light source for inducing free radicals includes one or more of ordinary xenon lamp light source, mercury lamp light source, metal halide lamp light source, and laser; in the electric-induced free radical system, an external electrochemical workstation or power supply is used to induce free radicals; in the thermal-induced free radical system, the temperature range is 25°C to 400°C.

8. An inert gas-free radical intermediate, It is characterized in that The inert gas-free radical intermediate is a free radical intermediate containing C, H or O.

9. The method according to any one of claims 1 to 7, or the inert gas-free radical intermediate according to claim 8, is used in the fields of prolonging the life of free radicals and maintaining the chemical activity of free radicals, thereby being used in the detection of highly reactive oxygen species, the selective preparation of carbon dioxide reduction reaction products, and the degradation of pollutants by highly reactive oxygen groups.

Images