Strong inverse kinetic isotope effect observed in ammonia charge exchange reactions
Isotopic substitution has long been used to understand the detailed mechanisms of chemical reactions; normally the substitution of hydrogen by deuterium leads to a slower reaction. Here, we report our findings on the charge transfer collisions of cold Xe+ ions and two isotopologues of ammonia, NH3 a...
| Main Authors: | , , , , |
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| Format: | Journal article |
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Nature Research
2020
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| _version_ | 1826287608840323072 |
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| author | Petralia, LS Tsikritea, A Loreau, J Softley, TP Heazlewood, BR |
| author_facet | Petralia, LS Tsikritea, A Loreau, J Softley, TP Heazlewood, BR |
| author_sort | Petralia, LS |
| collection | OXFORD |
| description | Isotopic substitution has long been used to understand the detailed mechanisms of chemical reactions; normally the substitution of hydrogen by deuterium leads to a slower reaction. Here, we report our findings on the charge transfer collisions of cold Xe+ ions and two isotopologues of ammonia, NH3 and ND3. Deuterated ammonia is found to react more than three times faster than hydrogenated ammonia. Classical capture models are unable to account for this pronounced inverse kinetic isotope effect. Moreover, detailed ab initio calculations cannot identify any (energetically accessible) crossing points between the reactant and product potential energy surfaces, indicating that electron transfer is likely to be slow. The higher reactivity of ND3 is attributed to the greater density of states (and therefore lifetime) of the deuterated reaction complex compared to the hydrogenated system. Our observations could provide valuable insight into possible mechanisms contributing to deuterium fractionation in the interstellar medium. |
| first_indexed | 2024-03-07T02:01:13Z |
| format | Journal article |
| id | oxford-uuid:9d6cb7d5-89ec-4d44-be47-9758ad062249 |
| institution | University of Oxford |
| last_indexed | 2024-03-07T02:01:13Z |
| publishDate | 2020 |
| publisher | Nature Research |
| record_format | dspace |
| spelling | oxford-uuid:9d6cb7d5-89ec-4d44-be47-9758ad0622492022-03-27T00:43:07ZStrong inverse kinetic isotope effect observed in ammonia charge exchange reactionsJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:9d6cb7d5-89ec-4d44-be47-9758ad062249Symplectic Elements at OxfordNature Research2020Petralia, LSTsikritea, ALoreau, JSoftley, TPHeazlewood, BRIsotopic substitution has long been used to understand the detailed mechanisms of chemical reactions; normally the substitution of hydrogen by deuterium leads to a slower reaction. Here, we report our findings on the charge transfer collisions of cold Xe+ ions and two isotopologues of ammonia, NH3 and ND3. Deuterated ammonia is found to react more than three times faster than hydrogenated ammonia. Classical capture models are unable to account for this pronounced inverse kinetic isotope effect. Moreover, detailed ab initio calculations cannot identify any (energetically accessible) crossing points between the reactant and product potential energy surfaces, indicating that electron transfer is likely to be slow. The higher reactivity of ND3 is attributed to the greater density of states (and therefore lifetime) of the deuterated reaction complex compared to the hydrogenated system. Our observations could provide valuable insight into possible mechanisms contributing to deuterium fractionation in the interstellar medium. |
| spellingShingle | Petralia, LS Tsikritea, A Loreau, J Softley, TP Heazlewood, BR Strong inverse kinetic isotope effect observed in ammonia charge exchange reactions |
| title | Strong inverse kinetic isotope effect observed in ammonia charge exchange reactions |
| title_full | Strong inverse kinetic isotope effect observed in ammonia charge exchange reactions |
| title_fullStr | Strong inverse kinetic isotope effect observed in ammonia charge exchange reactions |
| title_full_unstemmed | Strong inverse kinetic isotope effect observed in ammonia charge exchange reactions |
| title_short | Strong inverse kinetic isotope effect observed in ammonia charge exchange reactions |
| title_sort | strong inverse kinetic isotope effect observed in ammonia charge exchange reactions |
| work_keys_str_mv | AT petralials stronginversekineticisotopeeffectobservedinammoniachargeexchangereactions AT tsikriteaa stronginversekineticisotopeeffectobservedinammoniachargeexchangereactions AT loreauj stronginversekineticisotopeeffectobservedinammoniachargeexchangereactions AT softleytp stronginversekineticisotopeeffectobservedinammoniachargeexchangereactions AT heazlewoodbr stronginversekineticisotopeeffectobservedinammoniachargeexchangereactions |