Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP
The photoreactions of diazabicyclo[2,2,2]octane (DABCO) and triisopropylamine (TIPA) with the sensitizers anthraquinone (AQ) and xanthone (XA) or benzophenone (BP) were investigated by time-resolved photo-CIDNP (photochemically induced dynamic nuclear polarization) experiments. By varying the radica...
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| Format: | Article |
| Language: | English |
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Beilstein-Institut
2013-02-01
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| Series: | Beilstein Journal of Organic Chemistry |
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| Online Access: | https://doi.org/10.3762/bjoc.9.46 |
| _version_ | 1818732611093135360 |
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| author | Martin Goez Isabell Frisch Ingo Sartorius |
| author_facet | Martin Goez Isabell Frisch Ingo Sartorius |
| author_sort | Martin Goez |
| collection | DOAJ |
| description | The photoreactions of diazabicyclo[2,2,2]octane (DABCO) and triisopropylamine (TIPA) with the sensitizers anthraquinone (AQ) and xanthone (XA) or benzophenone (BP) were investigated by time-resolved photo-CIDNP (photochemically induced dynamic nuclear polarization) experiments. By varying the radical-pair concentration, it was ensured that these measurements respond only to self-exchange reactions of the free amine-derived radicals (radical cations DH•+ or α-amino alkyl radicals D•) with the parent amine DH; the acid–base equilibrium between DH•+ and D• also plays no role. Although the sensitizer does not at all participate in the observed processes, it has a pronounced influence on the CIDNP kinetics because the reaction occurs through successive radical pairs. With AQ, the polarizations stem from the initially formed radical-ion pairs, and escaping DH•+ then undergoes electron self-exchange with DH. In the reaction sensitized with XA (or BP), the polarizations arise in a secondary pair of neutral radicals that is rapidly produced by in-cage proton transfer, and the CIDNP kinetics are due to hydrogen self-exchange between escaping D• and DH. For TIPA, the activation parameters of both self-exchange reactions were determined. Outer-sphere reorganization energies obtained with the Marcus theory gave very good agreement between experimental and calculated values of ∆G‡298. |
| first_indexed | 2024-12-17T23:36:19Z |
| format | Article |
| id | doaj.art-d25aac052db14f70b1d6d64b0cb3ebf4 |
| institution | Directory Open Access Journal |
| issn | 1860-5397 |
| language | English |
| last_indexed | 2024-12-17T23:36:19Z |
| publishDate | 2013-02-01 |
| publisher | Beilstein-Institut |
| record_format | Article |
| series | Beilstein Journal of Organic Chemistry |
| spelling | doaj.art-d25aac052db14f70b1d6d64b0cb3ebf42022-12-21T21:28:33ZengBeilstein-InstitutBeilstein Journal of Organic Chemistry1860-53972013-02-019143744610.3762/bjoc.9.461860-5397-9-46Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNPMartin Goez0Isabell Frisch1Ingo Sartorius2Institut für Chemie, Martin–Luther-Universität Halle–Wittenberg, Kurt–Mothes-Str. 2, 06120 Halle/Saale, GermanyInstitut für Chemie, Martin–Luther-Universität Halle–Wittenberg, Kurt–Mothes-Str. 2, 06120 Halle/Saale, GermanyInstitut für Chemie, Martin–Luther-Universität Halle–Wittenberg, Kurt–Mothes-Str. 2, 06120 Halle/Saale, GermanyThe photoreactions of diazabicyclo[2,2,2]octane (DABCO) and triisopropylamine (TIPA) with the sensitizers anthraquinone (AQ) and xanthone (XA) or benzophenone (BP) were investigated by time-resolved photo-CIDNP (photochemically induced dynamic nuclear polarization) experiments. By varying the radical-pair concentration, it was ensured that these measurements respond only to self-exchange reactions of the free amine-derived radicals (radical cations DH•+ or α-amino alkyl radicals D•) with the parent amine DH; the acid–base equilibrium between DH•+ and D• also plays no role. Although the sensitizer does not at all participate in the observed processes, it has a pronounced influence on the CIDNP kinetics because the reaction occurs through successive radical pairs. With AQ, the polarizations stem from the initially formed radical-ion pairs, and escaping DH•+ then undergoes electron self-exchange with DH. In the reaction sensitized with XA (or BP), the polarizations arise in a secondary pair of neutral radicals that is rapidly produced by in-cage proton transfer, and the CIDNP kinetics are due to hydrogen self-exchange between escaping D• and DH. For TIPA, the activation parameters of both self-exchange reactions were determined. Outer-sphere reorganization energies obtained with the Marcus theory gave very good agreement between experimental and calculated values of ∆G‡298.https://doi.org/10.3762/bjoc.9.46aminesCIDNPelectron transferfree radicalshydrogen transferketoneskineticsphotochemistryself-exchange |
| spellingShingle | Martin Goez Isabell Frisch Ingo Sartorius Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP Beilstein Journal of Organic Chemistry amines CIDNP electron transfer free radicals hydrogen transfer ketones kinetics photochemistry self-exchange |
| title | Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP |
| title_full | Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP |
| title_fullStr | Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP |
| title_full_unstemmed | Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP |
| title_short | Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP |
| title_sort | electron and hydrogen self exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo cidnp |
| topic | amines CIDNP electron transfer free radicals hydrogen transfer ketones kinetics photochemistry self-exchange |
| url | https://doi.org/10.3762/bjoc.9.46 |
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