CN114067921B - Acidity coefficient determination method and device - Google Patents
Acidity coefficient determination method and device Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 62
- 238000010494 dissociation reaction Methods 0.000 claims abstract description 163
- 230000005593 dissociations Effects 0.000 claims abstract description 163
- 239000002253 acid Substances 0.000 claims abstract description 120
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 33
- 230000007062 hydrolysis Effects 0.000 claims description 17
- 238000006460 hydrolysis reaction Methods 0.000 claims description 17
- -1 hydrogen ions Chemical class 0.000 claims description 14
- 239000001257 hydrogen Substances 0.000 claims description 13
- 229910052739 hydrogen Inorganic materials 0.000 claims description 13
- 125000000524 functional group Chemical group 0.000 claims description 12
- 150000003384 small molecules Chemical class 0.000 claims description 3
- 238000004364 calculation method Methods 0.000 description 39
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 description 33
- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 description 23
- 238000004090 dissolution Methods 0.000 description 13
- 239000005711 Benzoic acid Substances 0.000 description 12
- 235000010233 benzoic acid Nutrition 0.000 description 12
- 239000000126 substance Substances 0.000 description 10
- 230000008569 process Effects 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- 230000002378 acidificating effect Effects 0.000 description 6
- 238000007614 solvation Methods 0.000 description 6
- 238000004057 DFT-B3LYP calculation Methods 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 5
- 239000006185 dispersion Substances 0.000 description 5
- 238000005457 optimization Methods 0.000 description 5
- 230000009897 systematic effect Effects 0.000 description 5
- 239000007864 aqueous solution Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 150000007513 acids Chemical class 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 238000002479 acid--base titration Methods 0.000 description 1
- 150000001558 benzoic acid derivatives Chemical class 0.000 description 1
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000003776 cleavage reaction Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 238000000324 molecular mechanic Methods 0.000 description 1
- 230000007017 scission Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- MHSKRLJMQQNJNC-UHFFFAOYSA-N terephthalamide Chemical compound NC(=O)C1=CC=C(C(N)=O)C=C1 MHSKRLJMQQNJNC-UHFFFAOYSA-N 0.000 description 1
- 150000003503 terephthalic acid derivatives Chemical class 0.000 description 1
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- G—PHYSICS
- G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
- G16C—COMPUTATIONAL CHEMISTRY; CHEMOINFORMATICS; COMPUTATIONAL MATERIALS SCIENCE
- G16C10/00—Computational theoretical chemistry, i.e. ICT specially adapted for theoretical aspects of quantum chemistry, molecular mechanics, molecular dynamics or the like
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Abstract
The present disclosure relates to a method and apparatus for determining an acidity coefficient, the method comprising obtaining a target acid H m A is a first dissociation parameter when n-level dissociation occurs, wherein m and n are positive integers, and m is more than or equal to n; obtaining a second dissociation parameter when the reference acid HR is dissociated; obtaining a third dissociation parameter of the water; an n-stage dissociation acidity coefficient of the target acid is determined based on the first dissociation parameter, the second dissociation parameter, and the third dissociation parameter. The acidity coefficient determination method disclosed by the invention takes the dissociation parameter of water as a benchmark and the dissociation parameter of reference acid as a reference, so that the acidity coefficient of the target acid is solved.
Description
Technical Field
The disclosure relates to the technical field of acidity coefficient calculation, in particular to a method and a device for determining an acidity coefficient.
Background
The acidity coefficient pKa has important significance in research of coordination chemistry and biochemistry, can be used for determining the proton dissociation sequence of a molecular structure and presuming a reaction mechanism on one hand, and can be used for determining the self-consistency of acid-base titration data and presuming the acid-base property and functional group of a substance by referring to an experimental value on the other hand. Common methods for calculating pKa theory are thermodynamic cycle method, quantum chemical parameter method, group contribution method and contrast free energy method.
The thermodynamic cycle method adopts quantum chemistry to calculate dissociation and dissolution free energy, but the current calculation method directly solves the free energy in a liquid phase environment with limited precision, so classical thermodynamic cycle in physicochemical is adopted to convert liquid phase species related before and after the reaction into gas phase expansion calculation, thereby obtaining relatively accurate dissociation and dissolution free energy, and further converting pKa. The method has definite physical meaning, accurate calculation result, large data fluctuation, serious influence by molecular configuration, often singular value in calculation result, complicated calculation flow and large calculation resource consumption, and has long time and large cost for solving all electron groups by adopting a thermodynamic combination method for free energy of each species under gas phase condition, and can not be used for calculating a macromolecular structure.
According to the quantum chemistry parameter method, the pKa value of the molecule and the atomic charge on the functional group capable of dissociating protons on the molecule are in linear relation, and an empirical expression of the atomic charge of the functional group and the pKa of the molecule can be obtained through fitting a large amount of experimental data. Therefore, for a new molecule, the pKa of the molecule can be predicted by calculating the atomic charge of the new molecule, and the complex calculation flow of a thermodynamic cycle method is omitted. The method has good stability for predicting the pKa of the molecules in the same series, is convenient and quick to use after obtaining the empirical expression, but has poor precision and high risk, and cannot obtain a reliable result for a system which is not very conventional. Meanwhile, the method needs to carry out a large amount of experimental parameter research before application, is suitable for long-term deep exploration aiming at a certain system, and is not suitable for instant research.
The group contribution method is an empirical calculation method, and according to the current experimental data, the functional group capable of dissociating protons and the groups connected around the functional group are associated with the change relation of pKa to obtain an empirical expression. When a new molecular structure is entered into the program, the program automatically performs radical cleavage, empirically inferring the pKa value of a functional group somewhere in the molecule from the radical contribution or rapid molecular mechanics calculations. The more mature software is now propKa, H++, chemDraw, etc. The method can obtain the pKa value of the molecule while knowing the molecular structure, but the results can only be used for making some simple qualitative judgment, the accuracy is general, the reliability is low, and the error result can be obtained. Meanwhile, the software generally only recognizes the pKa value of the conventional acid-base substance, and the result cannot be obtained for a more unfamiliar system.
The comparative free energy method is a pKa value calculation method with the best comprehensive performance. From the thermodynamic point of view, the traditional acidolysis equilibrium formula is considered, and the total charge numbers at the left side and the right side of the reaction formula are balanced, but the charge polarity is not kept, so that larger deviation exists between the direct calculation of the dissociation dissolution free energy and the actual situation. Therefore, another reference acid with known pKa is introduced at the left side and the right side of the dissociation equation, and the two acids are considered to have proton exchange reaction, so that the charge polarities at the two ends of the equation are balanced, and the calculation accuracy is improved; and then, the free energy of molecular dissociation and dissolution is directly calculated in a solvation environment, so that complicated calculation flow of a quantum chemical circulation method is omitted, meanwhile, the adoption of a very large electronic group is avoided, and the problem that a macromolecular structure cannot be calculated is solved. However, the calculation results show that even if the improvement is introduced, larger systematic errors still exist, and the reproducibility of the calculation and experimental results is poor. This reflects the problem that, as with the thermodynamic cycle method, it is difficult to calculate the dissociation dissolution free energy by means of quantitative calculation alone. Therefore, the second reference acid with known pKa value is introduced again to convert the dissolution dissociation free energy which needs to be directly solved into the relative free energy, thereby achieving the purpose of eliminating the systematic error. Such an improvement strategy was very successful and the developer tested 106 carboxylic acids and 70 alcohol phenols with good pKa reproducibility.
However, the contrast free energy method also has the problems of undefined physical meaning and poor data stability. First, the introduction of the first reference acid, while balancing the polarity of the proton dissociation equation, after all, does not have the presence of the second acidic species in the solution system, and does lack physical meaning. Secondly, although the second reference acid is introduced to convert the absolute energy of dissociation dissolution to be solved into relative energy, so as to achieve the purpose of eliminating systematic errors, the selection of the reference acid is not limited in theory, and therefore, the selection of the reference acid can lead to larger variation of calculation results. Thus, the developer has selected the references in studying the acid or alcohol system, respectively, through numerous empirical formula attempts and matches, and established the empirical expression, but neither the selected reference acid nor the reference alcohol are common substances, and obviously are not necessarily suitable for more complex systems.
Disclosure of Invention
The method and the device for determining the acidity coefficient aim to solve the problems of poor adaptability, high calculation cost and low calculation precision existing in the existing acidity coefficient calculation method.
In order to achieve the above object, the present disclosure provides a method for determining an acidity coefficient, the method comprising:
obtaining target acid H m A is a first dissociation parameter when n-level dissociation occurs, wherein m and n are positive integers, and m is more than or equal to n;
obtaining a second dissociation parameter when the reference acid HR is dissociated;
obtaining a third dissociation parameter of the water;
an n-stage dissociation acidity coefficient of the target acid is determined based on the first dissociation parameter, the second dissociation parameter, and the third dissociation parameter.
Optionally, the first dissociation parameter comprises a target acid H m A first gibbs free energy in the n-level dissociation state and a second gibbs free energy in the n-1 level dissociation state;
the second dissociation parameter comprises the pKa value of the reference acid HR, the third gibbs free energy in the non-dissociated state and the fourth gibbs free energy in the dissociated state;
the third dissociation parameters include the pKa value of water, the gibbs free energy at the time of dissociation of water, and the gibbs free energy of hydrogen ions generated by dissociation of water.
Optionally, the first gibbs free energy, the second gibbs free energy, the third gibbs free energy, and the fourth gibbs free energy are all gibbs free energies in solution.
Optionally, the determining the n-stage dissociation acidity coefficient of the target acid based on the first dissociation parameter, the second dissociation parameter, and the third dissociation parameter includes:
based on the first, second and third dissociation parameters, calculating an n-stage dissociation acidity coefficient of the target acid according to the following formula:
wherein,for the first Gibbs free energy, +.>For the second Gibbs free energy, +.>Is the third Gibbs free energy (HR) aq ) Being the fourth Gibbs free energy, pKa HR For the pKa of the reference acid, 14 is the pKa of water and 1329 is the sum of the gibbs free energy at the time of hydrolysis and the gibbs free energy of the hydrogen ions generated by the hydrolysis.
Optionally, the reference acid is a small molecule analog of the target acid.
Optionally, the reference acid satisfies at least one of the following conditions:
the reference acid has a similar molecular structure as the target acid;
the type of the functional group dissociated by the reference acid is the same as the type of the functional group dissociated by the target acid;
the total number of atoms in the molecular structure of the reference acid is not more than 200.
The present disclosure also provides a device for determining an acidity coefficient, the device comprising:
a first acquisition module for acquiring the target acid H m A is a first dissociation parameter when n-level dissociation occurs, wherein m and n are positive integers, and m is more than or equal to n;
the second acquisition module is used for acquiring a second dissociation parameter when the reference acid HR is dissociated;
the third acquisition module is used for acquiring a third dissociation parameter of the water;
a determining module for determining an n-stage dissociation acidity coefficient of the target acid based on the first dissociation parameter, the second dissociation parameter, and the third dissociation parameter.
Optionally, the first acquisition module includes: the first acquisition submodule is used for acquiring a first Gibbs free energy of the target acid in an n-level dissociation state; a second acquisition submodule for acquiring a second gibbs free energy of the target acid in an n-1 level dissociation state;
the second acquisition module includes: a third acquisition sub-module for acquiring the pKa value of the reference acid; a fourth obtaining submodule, configured to obtain a third gibbs free energy of the reference acid in a non-dissociated state; a fifth obtaining submodule, configured to obtain a fourth gibbs free energy of the reference acid in a dissociated state;
the third acquisition module includes: a sixth acquisition submodule for acquiring the pKa value of the water; a seventh acquisition submodule for acquiring gibbs free energy at the time of hydrolysis; and an eighth acquisition submodule for acquiring gibbs free energy of hydrogen ions generated by the water dissociation.
Optionally, the first gibbs free energy, the second gibbs free energy, the third gibbs free energy, and the fourth gibbs free energy are all gibbs free energies in solution.
Optionally, the determining module is configured to calculate the n-stage dissociation acidity coefficient of the target acid according to the following formula:
wherein,for the first Gibbs free energy, +.>For the second Gibbs free energy, +.>Is the third Gibbs free energy (HR) aq ) Being the fourth Gibbs free energy, pKa HR For the pKa of the reference acid, 14 is the pKa of water and 1329 is the sum of the gibbs free energy at the time of hydrolysis and the gibbs free energy of the hydrogen ions generated by the hydrolysis.
Through the technical scheme, the acidity coefficient determination method disclosed by the invention takes the dissociation parameter of water as a benchmark and the dissociation parameter of reference acid as a reference, so that the acidity coefficient of the target acid is solved.
Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.
Detailed Description
The following describes specific embodiments of the present disclosure in detail. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.
A first aspect of the present disclosure provides a method of determining an acidity coefficient, the method comprising: obtaining target acid H m A is a first dissociation parameter when n-level dissociation occurs, wherein m and n are positive integers, and m is more than or equal to n; obtaining a second dissociation parameter when the reference acid HR is dissociated; obtaining a third dissociation parameter of the water; an n-stage dissociation acidity coefficient of the target acid is determined based on the first dissociation parameter, the second dissociation parameter, and the third dissociation parameter.
In the method, the dissociation parameters of water are taken as the benchmark, the dissociation parameters of reference acid are taken as the reference, and the solution of the acidity coefficient of the target acid is realized.
In accordance with the present disclosure, the first, second, and third dissociation parameters may vary within a range, e.g., the first dissociation parameter may appear to include the target acid H m A first gibbs free energy in the n-level dissociation state and a second gibbs free energy in the n-1 level dissociation state; the second dissociation parameter may include the pKa value of the reference acid HR, the third gibbs free energy in the non-dissociated state, and the fourth gibbs free energy in the dissociated state; the third dissociation parameter may include the pKa value of water, the gibbs free energy at the time of dissociation, and the gibbs free energy of the hydrogen ions generated by dissociation.
According to the present disclosure, in order to further enhance the accuracy of the acidity coefficient calculation result, it is preferable that the first gibbs free energy, the second gibbs free energy, the third gibbs free energy, and the fourth gibbs free energy are gibbs free energies in a solution state.
In the present disclosure, specifically, the gibbs free energy of the target acid and the reference acid in each dissociation state can be obtained by methods commonly used in the art, for example, can be obtained by using quantum chemical calculation software.
According to the present disclosure, when determining the n-stage dissociation acidity coefficient of the target acid based on the first dissociation parameter, the second dissociation parameter, and the third dissociation parameter, the n-stage dissociation acidity coefficient of the target acid may be calculated based on the first dissociation parameter, the second dissociation parameter, and the third dissociation parameter according to the following formula:
wherein,for the first Gibbs free energy, +.>For the second Gibbs free energy, +.>Is the third Gibbs free energy (HR) aq ) Being the fourth Gibbs free energy, pKa HR For the pKa of the reference acid, 14 is the pKa of water and 1329 is the sum of the gibbs free energy at the time of hydrolysis and the gibbs free energy of the hydrogen ions generated by the hydrolysis.
The inventors of the present disclosure found that dissociation of an acidic species in an aqueous solution is polar in the presence of water molecules, in that the water molecules can dissociate into hydrogen ions and hydroxyl radicals and form immobilized ion products 10 -14 . Thus, the dissociation of the acidic species is in fact the hydrolysis of the dissociated OH - H abstracting acidic substances + And (3) a process of generating water, wherein the process is repeated until the chemical potential is balanced. In addition, in order to eliminate systematic errors caused by inaccurate calculation of the dissociation dissolution free energy Δg, a reference acid is introduced.
Next, the present disclosure will explain the principle and rationality of the acidity coefficient determination method of the present disclosure with HA as the target acid and HR as the reference acid:
based on the findings of the inventors of the present disclosure, it can be considered that the target acid and the reference acid exist in the aqueous solution in the following balance:
so that there is a number of the steps,
because of the presence of the metal-oxide-coated metal particles,
wherein,has an accurate experimental value of 89.89 KJ/mol->There are also accurate experimental values of 1139.35KJ/mol, and therefore,
meanwhile, dissociation of an acidic substance in an aqueous solution is constrained by the ionic product of water, and therefore, the pKa of a target acid can be calculated with reference to the dissociation of water:
wherein,has an accurate experimental value of 99.85KJ/mol and the ion product of the corresponding water is Kw=1.01X10 14 pKa of then H2O 14.0. So that there is a number of the steps,
the system error is eliminated by using the comparison quantity, and can be obtained,
then the first time period of the first time period,
wherein all units of energy are KJ/mol.
In the present disclosure, in particular, in order to further enhance the accuracy of the acidity coefficient calculation result, it is preferable that the reference acid is a small molecule analog of the target acid.
Further preferably, the reference acid satisfies at least one of the following conditions: the reference acid has a similar molecular structure as the target acid; the type of the functional group dissociated by the reference acid is the same as the type of the functional group dissociated by the target acid; the total number of atoms in the molecular structure of the reference acid is not more than 200.
In the present disclosure, specifically, unlike the comparative free energy method, reference acids suitable for carboxylic acid and alcohol-phenol systems are screened and fitted through a large number of calculations, the method of the present disclosure may not require specifying the type of reference acid, and only requires selecting a reference acid matching with a target acid according to a reference acid selection rule, so that the method of the present disclosure can omit a large number of research works for specifying the reference acid in the early stage, and can significantly reduce the cost of calculating the acidity coefficient.
The acidity coefficient determination method disclosed by the invention is based on the dissociation essence of acidic substances in aqueous solution, and aims at solving the pKa of target acid by taking the ionic product of water as a reference and the pKa of a small molecular analogue as a reference. Compared with a comparison free energy method, the method disclosed by the invention is more flexible to use, has a wider application range and has a stricter physical meaning. Because the systematic errors are eliminated by adopting the comparison quantity, the calculation result of the method has better data stability compared with a thermodynamic cycle method, and reduces the sensitivity to the Gibbs free energy solving precision, thereby realizing that a more reliable pKa calculation result is obtained under lower calculation cost, and having higher calculation efficiency. Also because the computational cost of this method is relatively low, it can handle larger molecular structures relative to thermodynamic cycling. Meanwhile, compared with empirical parameter methods such as a quantum chemical parameter method and a group contribution method, the method disclosed by the invention has better solving precision when solving a macromolecular structure.
Table 1 schematically shows experimental pKa values for 16 common target acids, and calculated pKa values calculated using the methods of the present disclosure:
TABLE 1
As can be seen from table 1, the method of the present disclosure can be applied to various systems of materials, and can calculate the acidity coefficient of macromolecular materials, with low calculation cost and high calculation accuracy.
A second aspect of the present disclosure provides an acidity coefficient determining device, comprising: a first acquisition module for acquiring the target acid H m A is a first dissociation parameter when n-level dissociation occurs, wherein m and n are positive integers, and m is more than or equal to n; the second acquisition module is used for acquiring a second dissociation parameter when the reference acid HR is dissociated; the third acquisition module is used for acquiring a third dissociation parameter of the water; a determining module for determining an n-stage dissociation acidity coefficient of the target acid based on the first dissociation parameter, the second dissociation parameter, and the third dissociation parameter.
Optionally, the first obtaining module may include: the first acquisition submodule is used for acquiring a first Gibbs free energy of the target acid in an n-level dissociation state; a second acquisition submodule for acquiring a second gibbs free energy of the target acid in an n-1 level dissociation state; the second acquisition module may include: a third acquisition sub-module for acquiring the pKa value of the reference acid; a fourth obtaining submodule, configured to obtain a third gibbs free energy of the reference acid in a non-dissociated state; a fifth obtaining submodule, configured to obtain a fourth gibbs free energy of the reference acid in a dissociated state; the third acquisition module may include: a sixth acquisition submodule for acquiring the pKa value of the water; a seventh acquisition submodule for acquiring gibbs free energy at the time of hydrolysis; and an eighth acquisition submodule for acquiring gibbs free energy of hydrogen ions generated by the water dissociation.
Optionally, the first gibbs free energy, the second gibbs free energy, the third gibbs free energy, and the fourth gibbs free energy are all gibbs free energies in solution.
Optionally, the determining module is configured to calculate the n-stage dissociation acidity coefficient of the target acid according to the following formula:
wherein,for the first Gibbs free energy, +.>For the second Gibbs free energy, +.>Is the third Gibbs free energy (HR) aq ) Being the fourth Gibbs free energy, pKa HR For the pKa of the reference acid, 14 is the pKa of water and 1329 is the sum of the gibbs free energy at the time of hydrolysis and the gibbs free energy of the hydrogen ions generated by the hydrolysis.
The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereby. The materials, reagents, instruments and equipment involved in the embodiments of the present disclosure, unless otherwise specified, are all available commercially.
Example 1
The primary and secondary dissociation pKa values of terephthalic acid were calculated using benzoic acid as the reference acid and Gaussian09 and Gaussview5 as the calculation tools, respectively, using the following method.
(1) Solving the gibbs free energy of the initial structure of the target acid:
constructing an initial structure of a terephthalic acid molecule by using Gaussview5 software, performing structural optimization and frequency analysis on the initial structure of the terephthalic acid molecule by using Gaussview 09 software, adding dispersion correction and solvation correction in a calculation process, and directly obtaining the dissolution dissociation Gibbs free energy of the initial structure of the terephthalic acid molecule: 1600459KJ/mol (at B3LYP/TZVP grade);
(2) Solving the Gibbs free energy of the primary dissociation structure of the target acid:
constructing a molecular structure of the primary dissociation of the terephthalic acid by using Gaussview5 software, performing structural optimization and frequency analysis on the molecular structure of the primary dissociation of the terephthalic acid by using Gaussview 09 software, adding dispersion correction and solvation correction in a calculation process, and directly obtaining the free energy of dissolution and dissociation gibbs of the molecular structure of the primary dissociation of the terephthalic acid: 1599291KJ/mol (at B3LYP/TZVP grade).
(3) Solving the gibbs free energy of the target acid secondary dissociation structure:
constructing a molecular structure of secondary dissociation of terephthalic acid by using Gaussian 5 software, performing structural optimization and frequency analysis on the molecular structure of secondary dissociation of terephthalic acid by using Gaussian09 software, adding dispersion correction and solvation correction in the calculation process, and directly obtaining the dissolution dissociation gibbs free energy of the molecular structure of secondary dissociation of terephthalic acid: 1598115KJ/mol (at B3LYP/TZVP grade).
(4) Solving the gibbs free energy of the reference acid initial structure:
constructing an initial structure of a benzoic acid molecule by using Gaussview5 software, performing structural optimization and frequency analysis on the initial structure of the benzoic acid molecule by using Gaussview 09 software, adding dispersion correction and solvation correction in a calculation process, and directly obtaining the dissolution dissociation gibbs free energy of the initial structure of the benzoic acid molecule: 1105152KJ/mol (at B3LYP/TZVP grade).
(5) Solving the gibbs free energy of the primary dissociation structure of the reference acid:
constructing a molecular structure of the first dissociation of the benzoic acid by using Gaussview5 software, performing structural optimization and frequency analysis on the molecular structure of the first dissociation of the benzoic acid by using Gaussview 09 software, adding dispersion correction and solvation correction in a calculation process, and directly obtaining the free energy of dissolution and dissociation gibbs of the molecular structure of the first dissociation of the benzoic acid: 1103979KJ/mol (at B3LYP/TZVP grade).
(6) Solving the target acid primary dissociation pKa:
bringing the gibbs free energy of the initial structure of terephthalic acid and the gibbs free energy of the primary dissociation structure of benzoic acid, the gibbs free energy of the initial structure of benzoic acid and the gibbs free energy of the primary dissociation structure, and the pKa value of benzoic acid of 4.28 into a calculation formula of the disclosure to calculate the primary dissociation pKa of terephthalamide as:
the experimental report shows that the primary dissociation pKa of terephthalic acid is 3.54, and the error between the two is 10%, so that the primary dissociation pKa of terephthalic acid can be calculated more accurately by the method disclosed by the invention.
(7) Solving the target acid secondary dissociation pKa:
the Gibbs free energy of the primary dissociation structure and the Gibbs free energy of the secondary dissociation structure of terephthalic acid, the Gibbs free energy of the initial structure and the Gibbs free energy of the primary dissociation structure of benzoic acid, and the pKa value of benzoic acid of 4.28 are brought into the calculation formula of the disclosure, and the secondary dissociation pKa of terephthalic acid is calculated as:
the experimental report shows that the secondary dissociation pKa of terephthalic acid is 4.46, and the error between the two is 2%, so that the method can calculate the secondary dissociation pKa of terephthalic acid more accurately.
The preferred embodiments of the present disclosure have been described in detail above, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.
In addition, the specific features described in the foregoing embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present disclosure does not further describe various possible combinations.
Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.
Claims (4)
1. A method for determining an acidity coefficient, the method comprising:
obtaining target acid H m A is a first dissociation parameter when n-level dissociation occurs, wherein m and n are positive integers, and m is more than or equal to n;
obtaining a second dissociation parameter when the reference acid HR is dissociated;
obtaining a third dissociation parameter of the water;
determining an n-level dissociation acidity coefficient of the target acid based on the first dissociation parameter, the second dissociation parameter, and the third dissociation parameter;
the first dissociation parameter comprises the target acid H m A first gibbs free energy in the n-level dissociation state and a second gibbs free energy in the n-1 level dissociation state;
the second dissociation parameter comprises the pKa value of the reference acid HR, the third gibbs free energy in the non-dissociated state and the fourth gibbs free energy in the dissociated state;
the third dissociation parameter comprises the pKa value of water, the gibbs free energy at the time of dissociation, and the gibbs free energy of hydrogen ions generated by dissociation;
the first gibbs free energy, the second gibbs free energy, the third gibbs free energy and the fourth gibbs free energy are all gibbs free energies in a solution state;
the determining the n-stage dissociation acidity coefficient of the target acid based on the first dissociation parameter, the second dissociation parameter, and the third dissociation parameter includes:
based on the first, second and third dissociation parameters, calculating an n-stage dissociation acidity coefficient of the target acid according to the following formula:
wherein,for the first Gibbs free energy, +.>For the second Gibbs free energy, +.>Is the third Gibbs free energy, G (HR) aq ) Being the fourth Gibbs free energy, pKa HR For the pKa of the reference acid, 14 is the pKa of water and 1329 is the sum of the gibbs free energy at the time of hydrolysis and the gibbs free energy of the hydrogen ions generated by the hydrolysis.
2. The method of claim 1, wherein the reference acid is a small molecule analog of the target acid.
3. The method of claim 2, wherein the reference acid satisfies at least one of the following conditions:
the reference acid has a similar molecular structure as the target acid;
the type of the functional group dissociated by the reference acid is the same as the type of the functional group dissociated by the target acid;
the total number of atoms in the molecular structure of the reference acid is not more than 200.
4. An acidity factor determining device, characterized in that the device comprises:
a first acquisition module for acquiring the target acid H m A is a first dissociation parameter when n-level dissociation occurs, wherein m and n are positive integers, and m is more than or equal to n;
the second acquisition module is used for acquiring a second dissociation parameter when the reference acid HR is dissociated;
the third acquisition module is used for acquiring a third dissociation parameter of the water;
a determining module for determining an n-level dissociation acidity coefficient of the target acid based on the first dissociation parameter, the second dissociation parameter, and the third dissociation parameter;
the first acquisition module includes: the first acquisition submodule is used for acquiring a first Gibbs free energy of the target acid in an n-level dissociation state; a second acquisition submodule for acquiring a second gibbs free energy of the target acid in an n-1 level dissociation state;
the second acquisition module includes: a third acquisition sub-module for acquiring the pKa value of the reference acid; a fourth obtaining submodule, configured to obtain a third gibbs free energy of the reference acid in a non-dissociated state; a fifth obtaining submodule, configured to obtain a fourth gibbs free energy of the reference acid in a dissociated state;
the third acquisition module includes: a sixth acquisition submodule for acquiring the pKa value of the water; a seventh acquisition submodule for acquiring gibbs free energy at the time of hydrolysis; an eighth acquisition submodule for acquiring gibbs free energy of hydrogen ions generated by the hydrolysis;
the first gibbs free energy, the second gibbs free energy, the third gibbs free energy and the fourth gibbs free energy are all gibbs free energies in a solution state;
the determination module is used for calculating the n-level dissociation acidity coefficient of the target acid according to the following formula:
wherein,for the first Gibbs free energy, +.>For the second Gibbs free energy, +.>Is the third Gibbs free energy, G (HR) aq ) Being the fourth Gibbs free energy, pKa HR For the pKa of the reference acid, 14 is the pKa of water and 1329 is the sum of the gibbs free energy at the time of hydrolysis and the gibbs free energy of the hydrogen ions generated by the hydrolysis.
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