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- Title
Sequential Hydrogen Tunneling in o‐Tolylmethylene.
- Authors
Lohmiller, Thomas; Sarkar, Sujan K.; Tatchen, Jörg; Henkel, Stefan; Schleif, Tim; Savitsky, Anton; Sanchez‐Garcia, Elsa; Sander, Wolfram
- Abstract
o‐Tolylmethylene 1 is a metastable triplet carbene that rearranges to o‐xylylene 2 even at temperatures as low as 2.7 K via [1,4] H atom tunneling. Electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopical techniques were used to identify two conformers of 1 (anti and syn) in noble gas matrices and in frozen organic solutions. Conformer‐specific kinetic measurements revealed that the rate constants for the rearrangements of the anti and syn conformers of 1 are very similar. However, the orbital alignment in the syn conformer is less favorable for the hydrogen transfer reaction than the orbital configuration in the anti conformer. Our spectroscopic and quantum chemical investigations indicate that anti1 and syn1 rapidly interconvert via efficient quantum tunneling forming a rotational pre‐equilibrium. The subsequent second tunneling reaction, the [1,4] H migration from anti1 to 2, is rate‐limiting for the formation of 2. We here present an efficient strategy for the study of such tunneling equilibria.
- Subjects
ELECTRON nuclear double resonance; ELECTRON paramagnetic resonance spectroscopy; HYDROGEN transfer reactions; ELECTRON paramagnetic resonance; TUNNEL design &; construction
- Publication
Chemistry - A European Journal, 2021, Vol 27, Issue 71, p17873
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.202102010