scholarly journals Fast and Automated Identification of Reactions with Low Barriers: The Decomposition of 3-Hydroperoxypropanal

2021 ◽  
Author(s):  
Maria Harris Rasmussen ◽  
Mads Madsen ◽  
Jan H. Jensen
Keyword(s):  
Reaction Mechanism ◽  
Systematic Approach ◽  
Transition States ◽  
Semiempirical Methods ◽  
Reaction Products ◽  
Reaction Energy ◽  
Automated Identification ◽  
Reaction Discovery ◽  
Systematic Enumeration ◽  
Computational Resources

We show how fast semiempirical QM methods can be used to significantly decrease the CPU requirements for automated reaction mechanism discovery, using two different method for generating reaction products: graph-based systematic enumeration of all possible products and the meta-dynamics approach by Grimme (J. Chem. Theory. Comput. 2019, 15, 2847). We test the two approaches on the low-barrier reactions of 3-hydroperoxypropanal, which have been studied by a large variety of reaction discovery approaches and therefore provides a good benchmark. By using PM3 and GFN2-xTB for reaction energy and barrier screening the systematic approach identifies 64 reactions (out of 27,577 possible reactions) for DFT refinement, which in turn identifies the three reactions with lowest barriers plus a previously undiscovered reaction. With optimised hyperparameters meta-dynamics followed by PM3/GFN2-xTB-based screening identifies 15 reactions for DFT refinement, which in turn identifies the three reactions with lowest barrier. The number of DFT refinements can be further reduced to as little as six for both approaches by first verifying the transition states with GFN1-xTB. The main conclusion is that the semiempirical methods are accurate and fast enough to automatically identify promising candidates for DFT refinement for the low barrier reactions of 3-hydroperoxypropanal in about 15-30 minutes using relatively modest computational resources.

Fast and automated identification of reactions with low barriers: the decomposition of 3-hydroperoxypropanal

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Mads Koerstz ◽  
Maria H. Rasmussen ◽  
Jan H. Jensen
Keyword(s):  
Reaction Mechanism ◽  
Systematic Approach ◽  
Transition States ◽  
Semiempirical Methods ◽  
Reaction Products ◽  
Reaction Energy ◽  
Automated Identification ◽  
Reaction Discovery ◽  
Systematic Enumeration ◽  
Computational Resources

We show how fast semiempirical QM methods can be used to significantly decrease the computational expense for automated reaction mechanism discovery, using two different method for generating reaction products: graph-based systematic enumeration of all possible products and the meta-dynamics approach by Grimme (J. Chem. Theory. Comput. 2019, 15, 2847). We test the two approaches on the low-barrier reactions of 3-hydroperoxypropanal, which have been studied by a large variety of reaction discovery approaches and therefore provides a good benchmark. By using PM3 and GFN2-xTB for reaction energy and barrier screening the systematic approach identifies 64 reactions (out of 27,577 possible reactions) for DFT refinement, which in turn identifies the three reactions with lowest barriers plus a previously undiscovered reaction. With optimized hyperparameters meta-dynamics followed by PM3/GFN2-xTB-based screening identifies 15 reactions for DFT refinement, which in turn identifies the three reactions with lowest barrier. The number of DFT refinements can be further reduced to as little as six for both approaches by first verifying the transition states with GFN1-xTB. The main conclusion is that the semiempirical methods are accurate and fast enough to automatically identify promising candidates for DFT refinement for the low barrier reactions of 3-hydroperoxypropanal in about 15-30 minutes using relatively modest computational resources.

scholarly journals Fast and Automated Identification of Reactions with Low Barriers: The Decomposition of 3-Hydroperoxypropanal

2021 ◽  
Author(s):  
Maria Harris Rasmussen ◽  
Mads Madsen ◽  
Jan H. Jensen
Keyword(s):  
Reaction Mechanism ◽  
Systematic Approach ◽  
Transition States ◽  
Semiempirical Methods ◽  
Reaction Products ◽  
Reaction Energy ◽  
Automated Identification ◽  
Reaction Discovery ◽  
Systematic Enumeration ◽  
Computational Resources

<div> <div> <div> <p>We show how fast semiempirical QM methods can be used to significantly decrease the CPU requirements for automated reaction mechanism discovery, using two different method for generating reaction products: graph-based systematic enumeration of all possible products and the meta-dynamics approach by Grimme (<i>J. Chem. Theory. Comput</i>. 2019, 15, 2847). We test the two approaches on the low-barrier reactions of 3-hydroperoxypropanal, which have been studied by a large variety of reaction discovery approaches and therefore provides a good benchmark. By using PM3 and GFN2-xTB for reaction energy and barrier screening the systematic approach identifies 64 reactions (out of 27,577 possible reactions) for DFT refinement, which in turn identifies the three reactions with lowest barriers plus a previously undiscovered reaction. With optimised hyperparameters meta-dynamics followed by PM3/GFN2-xTB-based screening identifies 15 reactions for DFT refinement, which in turn identifies the three reactions with lowest barrier. The number of DFT refinements can be further reduced to as little as six for both approaches by first verifying the transition states with GFN1-xTB. The main conclusion is that the semiempirical methods are accurate and fast enough to automatically identify promising candidates for DFT refinement for the low barrier reactions of 3-hydroperoxypropanal in a few hours using modest computational resources. </p> </div> </div> </div>

scholarly journals Fast and Automated Identification of Reactions with Low Barriers: The Decomposition of 3-Hydroperoxypropanal

2021 ◽  
Author(s):  
Maria Harris Rasmussen ◽  
Mads Madsen ◽  
Jan H. Jensen
Keyword(s):  
Reaction Mechanism ◽  
Systematic Approach ◽  
Transition States ◽  
Semiempirical Methods ◽  
Reaction Products ◽  
Reaction Energy ◽  
Automated Identification ◽  
Reaction Discovery ◽  
Systematic Enumeration ◽  
Computational Resources

<div> <div> <div> <p>We show how fast semiempirical QM methods can be used to significantly decrease the CPU requirements for automated reaction mechanism discovery, using two different method for generating reaction products: graph-based systematic enumeration of all possible products and the meta-dynamics approach by Grimme (<i>J. Chem. Theory. Comput</i>. 2019, 15, 2847). We test the two approaches on the low-barrier reactions of 3-hydroperoxypropanal, which have been studied by a large variety of reaction discovery approaches and therefore provides a good benchmark. By using PM3 and GFN2-xTB for reaction energy and barrier screening the systematic approach identifies 64 reactions (out of 27,577 possible reactions) for DFT refinement, which in turn identifies the three reactions with lowest barriers plus a previously undiscovered reaction. With optimised hyperparameters meta-dynamics followed by PM3/GFN2-xTB-based screening identifies 15 reactions for DFT refinement, which in turn identifies the three reactions with lowest barrier. The number of DFT refinements can be further reduced to as little as six for both approaches by first verifying the transition states with GFN1-xTB. The main conclusion is that the semiempirical methods are accurate and fast enough to automatically identify promising candidates for DFT refinement for the low barrier reactions of 3-hydroperoxypropanal in a few hours using modest computational resources. </p> </div> </div> </div>

[3,3] Sigmatropic Rearrangement of Some Fluorinated 1,5-Hexadienes

2002 ◽  
Vol 67 (10) ◽  
pp. 1517-1532 ◽  
Author(s):  
William R. Dolbier ◽  
Keith W. Palmer ◽  
Feng Tian ◽  
Piotr Fiedorow ◽  
Andrzej Zaganiaczyk ◽  
...  
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Transition States ◽  
Activation Parameters ◽  
Sigmatropic Rearrangement ◽  
Semiempirical Methods ◽  
Cope Rearrangement ◽  
Computational Studies ◽  
Stepwise Mechanism ◽  
Radical Intermediates

Fluorine atoms incorporated into 1,5-hexadiene molecule should influence the kinetic as well as the thermodynamic parameters of [3,3] sigmatropic rearrangement (Cope rearrangement). Within few decades is has been documented that this transformation proceeds in a concerted manner, rather than stepwise with some radical intermediates involved. Few new terminally fluorinated 1,5-hexadienes (compounds 3, 5A, 7, 9 and 5B) have been synthesized. The activation parameters of rearrangement have been determined and compared with those known for hydrocarbon analogues. While systems developing chair-like transition states (compounds 3 and 5) showed close similarity with hydrocarbon analogues (compound 1), those developing boat-like transition states (compounds 7, 9 and 5B) may proceed through radical stepwise mechanism. Computational studies of the transition states were carried out, showing that only ab initio methods (MP2 and especially DFT) can give approximate correlation with experimental data, whereas in the case of hydrocarbon analogues even simple semiempirical methods (AM1) were reliable enough to reproduce experimental results.

Product distributions and isotopic selectivities in ir multiphoton dissociation of pentafluoroiodoethane

1981 ◽  
Vol 59 (9) ◽  
pp. 1307-1310 ◽  
Author(s):  
E. Weinberg ◽  
M. Gauthier ◽  
P. A. Hackett ◽  
C. Willis
Keyword(s):  
Reaction Mechanism ◽  
Bond Cleavage ◽  
Thermal Dissociation ◽  
Infrared Multiphoton Dissociation ◽  
High Fluence ◽  
Reaction Products ◽  
Product Distributions ◽  
Multiphoton Dissociation

Infrared multiphoton dissociation of pentafluoroiodoethane leads to a complex array of reaction products. For photolysis in the v4 band the reaction mechanism involves C2F5—I bond cleavage followed by thermal dissociation of C2F5 radicals. For irradiation within the v3 band at high fluence, efficient secondary photolysis of C2F5 radicals is postulated. At lower fluences the dissociation is isotopically selective leading to C4F10 enriched in carbon-13.

scholarly journals Mechanical Properties and Reaction Characteristics of Al-ZrH2-PTFE Composites under Quasi-Static Compression

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 421 ◽  
Author(s):  
Jun Zhang ◽  
Xiang Fang ◽  
Yuchun Li ◽  
Zhongshen Yu ◽  
Junyi Huang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Reaction Mechanism ◽  
High Speed ◽  
Calorific Value ◽  
Reaction Rates ◽  
Zirconium Hydride ◽  
Reaction Products ◽  
Static Compression ◽  
Reaction Characteristics ◽  
Quasi Static Compression

To analyze the mechanical properties and reaction characteristics of Al-ZrH2-PTFE (aluminum-zirconium hydride-polytetrafluoroethylene) composites under quasi-static compression, five types of specimens with different ZrH2 contents (0%, 5%, 10%, 20% and 30%) were prepared by molding-vacuum sintering. The true stress-strain curves and reaction rates of the different specimens were measured using quasi-static compression. The specific reaction processes were recorded by a high-speed camera. The corresponding reaction products were characterized by the XRD phase analysis, the calorific value was tested by a Calorimeter, and the reaction mechanism was analyzed. According to the results, the strength of the composites increased first and then decreased with the increase in the content of ZrH2. It reached a maximum of 101.01 MPa at 5%. Violent reaction occurred, and special flames were observed during the reaction of the specimens with 5% ZrH2. With the increase in the content of ZrH2, the chemical reaction was hard to induce due to the reduction in strength and toughness of composites. The reaction mechanism of Al/ZrH2/PTFE reveals that high temperatures at crack tip induced the reaction of Al and PTFE. Subsequently, ZrH2 decomposed to release hydrogen and generate ZrC. Calorimetric experiment shows that the calorific value of Al/ZrH2/PTFE with 20% ZrH2 is higher than that of Al/PTFE. The findings verify the potential of ZrH2 as an energetic additive for the enhancement of strength and release of the energy of the composites.

The Reactions of Aniline and Its Homologs as Accelerators of Vulcanization

1928 ◽  
Vol 1 (2) ◽  
pp. 307-340
Author(s):  
Takeo Kimishima
Keyword(s):  
Reaction Mechanism ◽  
Chemical Reaction ◽  
Satisfactory Result ◽  
Chemical Change ◽  
The Other ◽  
Chemical Effect ◽  
Reaction Products ◽  
Thermal Change ◽  
Points Of View ◽  
The One

Abstract The accelerating action of aniline and its homologs can be considered from two points of view. The one is whether there are exothermic phenomena caused by the accelerators and the effect of those phenomena upon vulcanization. The other is the chemical effect upon vulcanization caused by reaction products derived as a result of chemical reaction of an accelerator and sulfur. In other words, the object of consideration in the former is the effect of thermal change, while that in the latter is the effect caused by chemical change. Leaving the former for later discussion, the writer will first describe the result of his experiments concerning the reaction products of accelerators and sulfur and the effect of these products upon vulcanization. In an investigation of this kind it is extremely difficult to extract and determine the effective elements from material derived from an accelerator in the process of vulcanizing reactions of rubber. No case has yet been known where a satisfactory result was realized by such a method. Therefore, the writer has first taken up the investigations of reactions of an accelerator with sulfur and by separating and refining each of the various reaction products approached the matter of vulcanization itself, and under various conditions caused these reaction products to act upon rubber. Thus the writer has followed the plan of establishing the reaction mechanism of accelerators by seeing the changes, both chemical and physical, together with their effect upon vulcanization.

scholarly journals Ab initio study of the mechanism of the reaction ClO + O --> Cl + O2

2021 ◽  
Vol 66 (1) ◽  
Author(s):  
S. Naskar ◽  
G. Nandi ◽  
T. K. Ghosh
Keyword(s):  
Reaction Mechanism ◽  
Ab Initio ◽  
Minimum Energy ◽  
Transition States ◽  
Basis Set ◽  
Heat Of Reaction ◽  
Minimal Basis ◽  
Dissociation Energies ◽  
Correlation Consistent ◽  
Equilibrium Geometries

Abstract. Ab initio investigation on the reaction mechanism of ClO + O --> Cl + O2 reaction has been performed using correlation consistent triple zeta basis set. The geometry and frequency of the reactants, products, minimum energy geometries and transition states are obtained using MP2 method and energetics are obtained at the QCISD(T)//MP2 level of theory. Primarily, a possible reaction mechanism is obtained on the basis on IRC calculations using MP2 level of theory. To obtain true picture of the reaction path, we performed IRC calculations using CASSCF method with a minimal basis set 6-31G**. Some new equilibrium geometries and transition states have been identified at the CASSCF level. Energetics are also obtained at the QCISD(T)//CASSCF method. Possible reaction paths have been discussed, which are new in literature. Heat of reaction is found to be consistent with the experimental data. Bond dissociation energies to various dissociation paths are also reported.

scholarly journals Organoborierung von Alkinylstannanen, XIV Organoborierung von Bis(alkinyl)stannanen: Mechanismus und Anwendung der 119Sn–NMR-Spektroskopie/ Organoboration of Alkynylstannanes, XIV Organoboration of Bis(alkynyl)stannanes: Mechanism and Application of 119Sn NMR Spectroscopy

1984 ◽  
Vol 39 (8) ◽  
pp. 1037-1041 ◽  
Author(s):  
Susanna Kerschl ◽  
Bernd Wrackmeyer
Keyword(s):  
Quantitative Analysis ◽  
Reaction Mechanism ◽  
Nmr Spectroscopy ◽  
Product Distribution ◽  
Reaction Products ◽  
Nmr Data ◽  
119Sn Nmr ◽  
119Sn Nmr Spectroscopy

AbstractDimethylbis(phenylethynyl)stannane (1) reacts with trialkylboranes, BR3 (2), to give bis(alkenyl stannanes (5) (R = C2H5), 1-bora-4-stanna-2,5-cyclohexadienes (6 ) (R = C2H5, C3H7i), 1- stanna-2,4-cyclopentadienes (7) (R = C2H5) and l-stanna-3-cyclopentenes (8 ) (R = CH3, C2H5). 13C and 119Sn NMR data prove the structure of the reaction products (5 to 8 ). 119Sn NMR is useful (i) for following the course of the reaction (mechanism!) and (ii) for quantitative analysis of the product distribution. Deorganoboration reactions play an important role in the formation of the various heterocyclic systems.

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