Method for detecting content of primary hydroxyl group
By using anhydride derivatization reagents and 1H NMR spectroscopy, the accuracy problem in detecting primary hydroxyl content in polyethers has been solved, realizing a simple and efficient detection method applicable to the analysis of primary hydroxyl content in block polyethers and random polyethers.
Patent Information
- Application Number
- CN202510996320.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-18
- Publication Date
- 2025-10-31
AI Technical Summary
Existing technologies make it difficult to accurately detect the content of primary hydroxyl groups in polyethers, which affects material performance optimization and cost control.
The sample to be analyzed was derivatized using an anhydride-based derivatization reagent. Combined with 1H NMR spectroscopy, the content of primary hydroxyl groups was calculated by the ratio of the integrated area of the peaks at chemical shifts δ of 4.20 and 5.00.
It achieves highly accurate and simple detection of primary hydroxyl content, avoids the interference of moisture on test results, and is suitable for the detection of block polyethers and random polyethers.
Smart Images
Figure CN120870210A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of materials analysis, and specifically to a method for detecting the content of primary hydroxyl groups. Background Technology
[0002] Polyethers can be classified into block polyethers and random polyethers based on the arrangement of ethylene oxide (EO) and propylene oxide (PO) in their main chain structure. The primary hydroxyl content in block polyethers directly affects their chemical reactivity, final material properties, and applicable scenarios. In high-end applications, precisely controlling the primary hydroxyl ratio is one of the core parameters for optimizing performance and cost. For example, high-primary-hydroxyl polyethers in wind turbine blade coatings can balance rapid curing and long-term weather resistance, while in the metal cleaning industry, the primary hydroxyl content of isomeric alcohol block polyethers serves as an important structural basis for balancing low-foaming performance and solubility. Therefore, analyzing and detecting the primary-to-secondary hydroxyl ratio of polyethers has significant practical value for controlling product quality. Summary of the Invention
[0003] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for detecting the content of primary hydroxyl groups, which has the advantages of high accuracy, simple steps and easy operation.
[0004] To solve the above problems, the technical solution adopted by the present invention is as follows:
[0005] A method for detecting the content of primary hydroxyl groups includes the following steps:
[0006] The sample to be analyzed is reacted with an anhydride-based derivatization reagent to obtain a derivatized sample;
[0007] The derivatized sample was dissolved in a deuterated reagent to obtain the test sample;
[0008] The test sample is sent into a nuclear magnetic resonance spectrometer for proton spectrum testing to obtain proton nuclear magnetic resonance spectrum data.
[0009] The primary hydroxyl content is calculated after the baseline is corrected, peaks are determined, and peaks are integrated on the proton NMR spectrum data. The formula for calculating the primary hydroxyl content is: [(I1÷2) / (I1÷2+I2)]×100%, where I1 is the integrated area of the peak with chemical shift δ of 4.20 and I2 is the integrated area of the peak with chemical shift δ of 5.00.
[0010] In some possible implementations, the sample to be analyzed comprises block polyether.
[0011] In some possible implementations, the number-average molecular weight of the block polyether is 200-2000.
[0012] In some possible implementations, the mass ratio of the sample to be analyzed to the anhydride derivatizing reagent is 1:1-20.
[0013] In some possible implementations, the anhydride derivatizing agent is selected from at least one of acetic anhydride, acetyl chloride, and phthalic anhydride.
[0014] In some possible implementations, the reaction temperature for obtaining the derivatized sample is 80–200°C, and the reaction time is at least 0.5 hours.
[0015] In some possible implementations, the mass ratio of the sample to be analyzed to the anhydride derivatizing reagent is 1:10, the reaction temperature to obtain the derivatized sample is 150°C, and the reaction time is 1.5 hours.
[0016] In some possible implementations, the mass ratio of the derivatized sample to the deuterated reagent is 1:1-50.
[0017] In some possible implementations, the deuterated reagent is deuterated chloroform, and the mass ratio of the derivatized sample to the deuterated reagent is 1:20.
[0018] In some possible implementations, a 600M nuclear magnetic resonance spectrometer is used for proton spectrum testing. The parameters for proton spectrum testing are as follows: observation frequency of 600.21 MHz, number of sampling points of 64k, spectral width of 11904 Hz, 90° pulse width of 9.3 μs, acquisition time of 2.75 s, number of empty scans of 2, and number of accumulations of 32.
[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0020] In this application, the sample is pretreated with an anhydride-based derivatization reagent, and then the primary hydroxyl content is detected by nuclear magnetic resonance (NMR) 1H spectroscopy. This avoids the interference of moisture on the primary hydroxyl content test results, thus making the detection method of this application highly accurate. Furthermore, the detection method of this application is simple and easy to operate.
[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description
[0022] Figure 1 This is a flowchart of a method for detecting the content of primary hydroxyl groups provided in an embodiment of this application.
[0023] Figure 2 The results are the 1H NMR spectra of 1,2-propanediol after acetic anhydride derivatization.
[0024] Figure 3The results are the 1H NMR spectra of the block polyether derived from phthalic anhydride.
[0025] Figure 4 The results are the 1H NMR spectra of the block polyether after acetyl chloride derivatization.
[0026] Figure 5 The results are the 1H NMR spectra of the block polyether derived from acetic anhydride. Detailed Implementation
[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
[0029] The following describes some embodiments of the present invention in detail. Unless otherwise specified, the following embodiments and features can be combined with each other.
[0030] One embodiment of this application provides a method for detecting the content of primary hydroxyl groups, comprising the following steps.
[0031] Step S101: React the sample to be analyzed with an anhydride-based derivatization reagent to obtain a derivatized sample. Derivatization treatment can avoid the interference of moisture on the test results.
[0032] In some embodiments, the sample to be analyzed comprises block polyether (EO / PO block polyether).
[0033] In some embodiments, the number-average molecular weight of the block polyether is 200-2000. For example, the number-average molecular weight of the block polyether can be any value between 200 and 550, or any value between 550 and 1800, or any value between 1800 and 2000. The selection of the molecular weight helps control the integrated area of the NMR spectrometer within an optimal range, thereby further improving the testing accuracy.
[0034] It is understood that the detection method of this application can be used to detect other organic compounds, including primary and secondary hydroxyl groups, such as 1,2-propanediol, glycerol, polyethylene glycol, and polypropylene glycol.
[0035] In some embodiments, the anhydride derivatizing reagent is selected from at least one of acetic anhydride, acetyl chloride, and phthalic anhydride. The selection of the specific types of anhydride derivatizing reagents mentioned above can yield relatively stable test results.
[0036] In some embodiments, the mass ratio of the sample to be analyzed to the anhydride derivatizing reagent is 1:1-20.
[0037] In some embodiments, the reaction temperature for obtaining the derivatized sample is 80–200°C, and the reaction time is at least 0.5 hours. These derivatization conditions are conducive to ensuring complete derivatization.
[0038] In some embodiments, the mass ratio of the sample to be analyzed to the anhydride derivatizing reagent is 1:10, the reaction temperature for obtaining the derivatized sample is 150°C, and the reaction time is 1.5 hours. The reaction conditions of this application help to ensure the derivatization effect while reducing the reaction time, thereby improving operational efficiency.
[0039] Step S102: Dissolve the derivatized sample in a deuterated reagent to obtain the test sample.
[0040] In some embodiments, the mass ratio of the derivatized sample to the deuterated reagent is 1:1-50.
[0041] In some embodiments, the deuterated reagent is deuterated chloroform, and the mass ratio of the derivatized sample to the deuterated reagent is 1:20.
[0042] Step S103: The test sample is sent into a nuclear magnetic resonance spectrometer for proton spectrum testing to obtain proton nuclear magnetic resonance spectrum data.
[0043] In some embodiments, a 600M nuclear magnetic resonance spectrometer was used for proton spectrum testing. The parameters for proton spectrum testing were as follows: observation frequency of 600.21 MHz, number of sampling points of 64k, spectral width of 11904 Hz, 90° pulse width of 9.3 μs, acquisition time of 2.75 s, number of empty scans of 2, and number of accumulations of 32.
[0044] Step S104: After correcting the baseline, determining the peaks, and integrating the peaks in the 1H NMR spectrum data, the primary hydroxyl content is calculated. The formula for calculating the primary hydroxyl content is: [(I1÷2) / (I1÷2+I2)]×100%, where I1 is the integrated area of the peak with a chemical shift δ of 4.20, and I2 is the integrated area of the peak with a chemical shift δ of 5.00.
[0045] In this application, the sample is pretreated with an anhydride-based derivatization reagent, and then the primary hydroxyl content is detected by nuclear magnetic resonance (NMR) 1H spectroscopy. This avoids the interference of moisture on the primary hydroxyl content test results, thus making the detection method of this application highly accurate. Furthermore, the detection method of this application is simple and easy to operate.
[0046] The following are detailed implementation methods.
[0047] Example 1
[0048] This embodiment examines 1,2-propanediol with a known proportion of primary hydroxyl groups to verify the accuracy of the method, as detailed below:
[0049] 1. Instruments and reagents
[0050] 600M nuclear magnetic resonance spectrometer (Bruker GmbH, Germany);
[0051] Deuterated chloroform was purchased from Qingdao Tenglong Microwave Technology Co., Ltd.; 1,2-propanediol and acetic anhydride were of analytical grade.
[0052] 2. Sample pretreatment
[0053] Derivatization: Take 0.20 g of the 1,2-propanediol sample to be analyzed into a 10 mL reaction flask with a cap, add 2.0 g of acetic anhydride, heat at 150 °C for 1.5 hours to obtain 2.2 g of derivatized sample.
[0054] Dissolve 0.03g of the derivatized sample in 0.6g of deuterated chloroform to obtain the test sample. That is, the mass ratio of the derivatized sample to the deuterated reagent is 1:20.
[0055] 3. Testing Methods
[0056] The samples before and after derivatization were analyzed by 600 MHz proton NMR spectroscopy. The proton NMR parameters were as follows: measurement temperature 25℃, observation frequency 600.21 MHz, number of sampling points 64 kJ, spectral width 11904 Hz, 90° pulse width 9.3 μs, acquisition time 2.75 s, number of blank scans 2, and number of accumulations 32. The obtained proton NMR data were processed using MetRenova software.
[0057] 4. Results Analysis
[0058] The primary hydroxyl content is calculated after the baseline is corrected, peaks are determined, and peaks are integrated on the proton NMR spectrum data. The formula for calculating the primary hydroxyl content is: [(I1÷2) / (I1÷2+I2)]×100%, where I1 is the integrated area of the peak with chemical shift δ of 4.20 and I2 is the integrated area of the peak with chemical shift δ of 5.00.
[0059] Figure 2 The images show the 1H NMR spectra of 1,2-propanediol after derivatization with acetic anhydride. 1,2-Propanediol possesses one primary hydroxyl group and one secondary hydroxyl group. For the primary hydroxyl group, due to the electron-withdrawing effect of the acetyl group on the shift of the methylene group attached to the terminal hydroxyl group of the block polyether, the derivatized spectrum shows a characteristic peak at chemical shift δ = 4.20, and the peak area is related to the number of primary hydroxyl groups in the sample. For the secondary hydroxyl group, due to the electron-withdrawing effect of the acetyl group on the shift of the methylene group attached to the terminal hydroxyl group of the block polyether, the derivatized spectrum shows a characteristic peak at chemical shift δ = 5.00, and the peak area is related to the number of secondary hydroxyl groups in the sample.
[0060] The peak area at chemical shift δ = 5.00 of the derivatized 1,2-propanediol was set to 1.00. Integrating, the peak area at chemical shift δ = 4.20 was found to be 2.02. Since the peak at chemical shift δ = 4.20 corresponds to two C-H bonds on the primary hydroxymethylene group at the end of the molecular chain, while the peak at chemical shift δ = 5.00 corresponds to one C-H bond on the secondary hydroxymethylene group at the end of the molecular chain, the primary hydroxyl content of the 1,2-propanediol sample was calculated to be [(2.02÷2) / (2.02÷2+1.00)]×100%=50.2%.
[0061] Example 2
[0062] The method described in Example 1 was used, except that the derivatizing reagent was changed to phthalic anhydride, and the sample to be analyzed was replaced with HMJM-1 (number average molecular weight 550), a block polyether from Zhejiang Huangma Technology Co., Ltd., which has a reserved PO ending in 1.0. Other parameters were the same as in Example 1. The chromatogram is shown below. Figure 3 The primary hydroxyl content was calculated to be [(0.47÷2) / (0.47÷2+1.00)]×100%=19.0%.
[0063] Example 3
[0064] The method described in Example 1 was used, except that the derivatization reagent was replaced with acetyl chloride, and the sample to be analyzed was replaced with another block polyether HMJM-2 (number average molecular weight 580) from Zhejiang Huangma Technology Co., Ltd., which has a reserved 1.8 PO ending. Other parameters were the same as in Example 1. The chromatogram is shown below. Figure 4 The primary hydroxyl content was calculated to be [(0.03÷2) / (0.03÷2+1.00)]×100%=1.5%.
[0065] Example 4
[0066] Using the method described in Example 1, acetic anhydride was used as the derivatization reagent. The sample to be analyzed was replaced with another block polyether, HMJM-3 (number average molecular weight 1800), from Zhejiang Huangma Technology Co., Ltd., which has a reserved 1.5 PO ending. The spectrum is shown in [reference needed]. Figure 5 The primary hydroxyl content was calculated to be [(0.02÷2) / (0.02÷2+1.00)]×100%=1.0%.
[0067] Based on the analysis of known structures, the results obtained by this method are quite close to the actual primary hydroxyl content. Furthermore, anhydride derivatizing reagents such as acetic anhydride, acetyl chloride, and phthalic anhydride all yield relatively stable test results. Acetic anhydride has advantages such as safety in use, high availability of raw materials, and low cost.
[0068] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.
Claims
1. A method for detecting the content of primary hydroxyl groups, characterized in that, Includes the following steps: The sample to be analyzed is reacted with an anhydride-based derivatization reagent to obtain a derivatized sample; The derivatized sample was dissolved in a deuterated reagent to obtain the test sample; The test sample is sent into a nuclear magnetic resonance spectrometer for proton spectrum testing to obtain proton nuclear magnetic resonance spectrum data. The primary hydroxyl content is calculated after the baseline is corrected, peaks are determined, and peaks are integrated on the proton NMR spectrum data. The formula for calculating the primary hydroxyl content is: [(I1÷2) / (I1÷2+I2)]×100%, where I1 is the integrated area of the peak with chemical shift δ of 4.20 and I2 is the integrated area of the peak with chemical shift δ of 5.
00.
2. The detection method as described in claim 1, characterized in that, The sample to be analyzed includes block polyether.
3. The detection method as described in claim 2, characterized in that, The number average molecular weight of the block polyether is 200-2000.
4. The detection method as described in claim 1, characterized in that, The mass ratio of the sample to be analyzed to the anhydride derivatizing reagent is 1:1-20.
5. The detection method as described in claim 1, characterized in that, The acid anhydride derivatizing reagent is selected from at least one of acetic anhydride, acetyl chloride, and phthalic anhydride.
6. The detection method as described in claim 4, characterized in that, The reaction temperature for obtaining the derivatized sample is 80-200℃, and the reaction time is at least 0.5 hours.
7. The detection method as described in claim 6, characterized in that, The mass ratio of the sample to be analyzed to the anhydride derivatizing reagent is 1:
10. The reaction temperature for obtaining the derivatized sample is 150℃, and the reaction time is 1.5 hours.
8. The detection method as described in claim 1, characterized in that, The mass ratio of the derivatized sample to the deuterated reagent is 1:1-50.
9. The detection method as described in claim 8, characterized in that, The deuterated reagent is deuterated chloroform, and the mass ratio of the derivatized sample to the deuterated reagent is 1:
20.
10. The detection method as described in claim 1, characterized in that, The proton spectrum was measured using a 600M nuclear magnetic resonance spectrometer. The parameters for the proton spectrum measurement were as follows: observation frequency of 600.21MHz, number of sampling points of 64k, spectral width of 11904Hz, 90° pulse width of 9.3μs, acquisition time of 2.75s, number of empty scans of 2, and number of accumulations of 32.