Reaction Rate Rules of Intramolecular H-Migration Reaction Class for R<sup>I</sup>OR<sup>II</sup>OO·Radicals in Ether Combustion
The intramolecular H-migration reaction of R<sup>I</sup>OR<sup>II</sup>OO· radicals constitute a key class of reactions in the low-temperature combustion mechanism of ethers. Despite this, there is a dearth of direct computations regarding the potential energy surface and rat...
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2024-09-01
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| author | Xiaohui Sun Zerong Li |
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| description | The intramolecular H-migration reaction of R<sup>I</sup>OR<sup>II</sup>OO· radicals constitute a key class of reactions in the low-temperature combustion mechanism of ethers. Despite this, there is a dearth of direct computations regarding the potential energy surface and rate constants specific to ethers, especially when considering large molecular systems and intricate branched-chain structures. Furthermore, combustion kinetic models for large molecular ethers generally utilize rate constants derived from those of structurally similar alcohols or alkane fuels. Consequently, chemical kinetic studies involve the calculation of energy barriers and rate rules for the intramolecular H-migration reaction class of R<sup>I</sup>OR<sup>II</sup>OO· radicals, which are systematically conducted using the isodesmic reaction method (IRM). The geometries of the species participating in these reactions are optimized, and frequency calculations are executed using the M06–X method in tandem with the 6–31+G(d,p) basis set by the Gaussian 16 program. Moreover, the M06–2X/6–31+G(d,p) method acts as the low-level ab initio method, while the CBS–QB3 method is utilized as the high-level ab initio method for calculating single-point energies. Rate constants at the high-pressure-limit are computed based on the reaction class transition state theory (RC-TST) by ChemRate program, incorporating asymmetric Eckart tunneling corrections for intramolecular H-migration reactions across a temperature range of 500 to 2000 K. It was found that the isodesmic reaction method gives accurate energy barriers and rate constants, and the rate constants of the H-migration reaction for R<sup>I</sup>OR<sup>II</sup>OO· radicals diverge from those of comparable reactions in alkanes and alcohol fuels. There are significant disparities in energy barriers and rate constants across the entire reaction classes of the H-migration reaction for R<sup>I</sup>OR<sup>II</sup>OO· radicals, necessitating the subdivision of the H-migration reaction into subclasses. Rate rules are established by averaging the rate constants of representative reactions for each subclass, which is pivotal for the advancement of accurate low-temperature combustion reaction mechanisms for ethers. |
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| spelling | doaj-art-075abca96c7444459d11d0b554ac003e2025-08-20T01:55:42ZengMDPI AGMolecules1420-30492024-09-012918438710.3390/molecules29184387Reaction Rate Rules of Intramolecular H-Migration Reaction Class for R<sup>I</sup>OR<sup>II</sup>OO·Radicals in Ether CombustionXiaohui Sun0Zerong Li1School of Energy Engineering, Shanxi College of Technology, Shuozhou 036000, ChinaCollege of Chemistry, Sichuan University, Chengdu 610064, ChinaThe intramolecular H-migration reaction of R<sup>I</sup>OR<sup>II</sup>OO· radicals constitute a key class of reactions in the low-temperature combustion mechanism of ethers. Despite this, there is a dearth of direct computations regarding the potential energy surface and rate constants specific to ethers, especially when considering large molecular systems and intricate branched-chain structures. Furthermore, combustion kinetic models for large molecular ethers generally utilize rate constants derived from those of structurally similar alcohols or alkane fuels. Consequently, chemical kinetic studies involve the calculation of energy barriers and rate rules for the intramolecular H-migration reaction class of R<sup>I</sup>OR<sup>II</sup>OO· radicals, which are systematically conducted using the isodesmic reaction method (IRM). The geometries of the species participating in these reactions are optimized, and frequency calculations are executed using the M06–X method in tandem with the 6–31+G(d,p) basis set by the Gaussian 16 program. Moreover, the M06–2X/6–31+G(d,p) method acts as the low-level ab initio method, while the CBS–QB3 method is utilized as the high-level ab initio method for calculating single-point energies. Rate constants at the high-pressure-limit are computed based on the reaction class transition state theory (RC-TST) by ChemRate program, incorporating asymmetric Eckart tunneling corrections for intramolecular H-migration reactions across a temperature range of 500 to 2000 K. It was found that the isodesmic reaction method gives accurate energy barriers and rate constants, and the rate constants of the H-migration reaction for R<sup>I</sup>OR<sup>II</sup>OO· radicals diverge from those of comparable reactions in alkanes and alcohol fuels. There are significant disparities in energy barriers and rate constants across the entire reaction classes of the H-migration reaction for R<sup>I</sup>OR<sup>II</sup>OO· radicals, necessitating the subdivision of the H-migration reaction into subclasses. Rate rules are established by averaging the rate constants of representative reactions for each subclass, which is pivotal for the advancement of accurate low-temperature combustion reaction mechanisms for ethers.https://www.mdpi.com/1420-3049/29/18/4387intramolecular H-migration reactionreaction rate rulesisodesmic reaction method (IRM)reaction class transition state theory (RC-TST) |
| spellingShingle | Xiaohui Sun Zerong Li Reaction Rate Rules of Intramolecular H-Migration Reaction Class for R<sup>I</sup>OR<sup>II</sup>OO·Radicals in Ether Combustion Molecules intramolecular H-migration reaction reaction rate rules isodesmic reaction method (IRM) reaction class transition state theory (RC-TST) |
| title | Reaction Rate Rules of Intramolecular H-Migration Reaction Class for R<sup>I</sup>OR<sup>II</sup>OO·Radicals in Ether Combustion |
| title_full | Reaction Rate Rules of Intramolecular H-Migration Reaction Class for R<sup>I</sup>OR<sup>II</sup>OO·Radicals in Ether Combustion |
| title_fullStr | Reaction Rate Rules of Intramolecular H-Migration Reaction Class for R<sup>I</sup>OR<sup>II</sup>OO·Radicals in Ether Combustion |
| title_full_unstemmed | Reaction Rate Rules of Intramolecular H-Migration Reaction Class for R<sup>I</sup>OR<sup>II</sup>OO·Radicals in Ether Combustion |
| title_short | Reaction Rate Rules of Intramolecular H-Migration Reaction Class for R<sup>I</sup>OR<sup>II</sup>OO·Radicals in Ether Combustion |
| title_sort | reaction rate rules of intramolecular h migration reaction class for r sup i sup or sup ii sup oo·radicals in ether combustion |
| topic | intramolecular H-migration reaction reaction rate rules isodesmic reaction method (IRM) reaction class transition state theory (RC-TST) |
| url | https://www.mdpi.com/1420-3049/29/18/4387 |
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