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Ab initio quantum mechanical calculation of the reaction probability for the Cl- + PH2Cl -> ClPH2 + Cl- reaction
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.ORCID iD: 0000-0002-1312-1202
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
2013 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 425, 134-140 p.Article in journal (Refereed) Published
Abstract [en]

The SN2 substitution reactions at phosphorus play a key role in organic and biological processes. Quantum molecular dynamics simulations have been performed to study the prototype reaction Cl-+PH2ClClPH2+Cl-, using one and two-dimensional models. A potential energy surface, showing an energy well for a transition complex, was generated using ab initio electronic structure calculations. The one-dimensional model is essentially reflection free, whereas the more realistic two-dimensional model displays involved resonance structures in the reaction probability. The reaction rate is almost two orders of magnitude smaller for the two-dimensional compared to the one-dimensional model. Energetic errors in the potential energy surface is estimated to affect the rate by only a factor of two. This shows that for these types of reactions it is more important to increase the dimensionality of the modeling than to increase the accuracy of the electronic structure calculation.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2013. Vol. 425, 134-140 p.
Keyword [en]
Nucleophilic substitution (S(N)2); Reaction probability; Quantum dynamics
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-210368DOI: 10.1016/j.chemphys.2013.08.011ISI: 000327443700016OAI: oai:DiVA.org:uu-210368DiVA: diva2:662195
Funder
Marcus and Amalia Wallenberg FoundationSwedish National Infrastructure for Computing (SNIC), p2011004
Available from: 2013-11-06 Created: 2013-11-06 Last updated: 2016-10-27Bibliographically approved
In thesis
1. Theoretical Studies of Seemingly Simple Chemical Reactions
Open this publication in new window or tab >>Theoretical Studies of Seemingly Simple Chemical Reactions
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Uppsala universitet, 2013. 38 p.
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-228291 (URN)
Presentation
2013-12-11, Å80101, Uppsala University, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2014-07-15 Created: 2014-07-09 Last updated: 2015-03-24Bibliographically approved
2. Theoretical Studies of Ground and Excited State Reactivity
Open this publication in new window or tab >>Theoretical Studies of Ground and Excited State Reactivity
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

To exemplify how theoretical chemistry can be applied to understand ground and excited state reactivity, four different chemical reactions have been modeled. The ground state chemical reactions are the simplest models in chemistry. To begin, a route to break down halomethanes through reactions with ground state cyano radical has been selected. Efficient explorations of the potential energy surfaces for these reactions have been carried out using the artificial force induced reaction algorithm. The large number of feasible pathways for reactions of this type, up to eleven, shows that these seemingly simple reactions can be quite complex. This exploration is followed by accurate quantum dynamics with reduced dimensionality for the reaction between Cland PH2Cl. The dynamics indicate that increasing the dimensionality of the model to at least two dimensions is a crucial step for an accurate calculation of the rate constant. After considering multiple pathways on a single potential energy surface, various feasible pathways on multiple surfaces have been investigated. As a prototype of these reactions, the thermal decomposition of a four-membered ring peroxide compound, called 1,2-dioxetane, which is the simplest model of chemi- and bioluminescence, has been studied. A detailed description of this model at the molecular level can give rise to a unified understanding of more complex chemiluminescence mechanisms. The results provide further details on the mechanisms and allow to rationalize the high ratio of triplet to singlet dissociation products. Finally, a thermal decomposition of another dioxetane-like compound, called Dewar dioxetane, has been investigated. This study allows to understand the effect of conjugated double bonds adjacent to the dioxetane moiety in the chemiluminescence mechanism of dioxetane. Our studies illustrate that no matter how complex a system is, theoretical chemistry can give a level of insight into chemical processes that cannot be obtained from other methods.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 86 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1179
Keyword
Chemical Reactivity, Computational Chemistry, Dynamics, Ground and Excited States, Chemiluminescence, Atmospheric Chemistry
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-232219 (URN)978-91-554-9036-2 (ISBN)
Public defence
2014-10-30, Häggsalen, Ångström laboratory, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2014-10-09 Created: 2014-09-15 Last updated: 2015-01-23Bibliographically approved

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