| Title: |
Hydrogen Delocalization in an Asymmetric Biomolecule: The Curious Case of Alpha-Fenchol |
| Authors: |
Medel, Robert; Springborn, Johann R.; Crittenden, Deborah L.; Suhm, Martin A.; Sanz, Maria Eugenia; 1Institut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstr. 6, 37077 Goettingen, Germany; j.springborn@stud.uni-goettingen.de (J.R.S.); msuhm@gwdg.de (M.A.S.); 2School of Physical and Chemical Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand; deborah.crittenden@canterbury.ac.nz |
| Contributors: |
Medel, Robert; Springborn, Johann R.; Crittenden, Deborah L.; Suhm, Martin A.; Sanz, Maria Eugenia; 1Institut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstr. 6, 37077 Goettingen, Germany; j.springborn@stud.uni-goettingen.de (J.R.S.); msuhm@gwdg.de (M.A.S.); 2School of Physical and Chemical Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand; deborah.crittenden@canterbury.ac.nz |
| Publisher Information: |
MDPI |
| Publication Year: |
2022 |
| Collection: |
Georg-August-Universität Göttingen: GoeScholar |
| Description: |
Rotational microwave jet spectroscopy studies of the monoterpenol α-fenchol have so far failed to identify its second most stable torsional conformer, despite computational predictions that it is only very slightly higher in energy than the global minimum. Vibrational FTIR and Raman jet spectroscopy investigations reveal unusually complex OH and OD stretching spectra compared to other alcohols. Via modeling of the torsional states, observed spectral splittings are explained by delocalization of the hydroxy hydrogen atom through quantum tunneling between the two non-equivalent but accidentally near-degenerate conformers separated by a low and narrow barrier. The energy differences between the torsional states are determined to be only 16(1) and 7(1) cm−1hc for the protiated and deuterated alcohol, respectively, which further shrink to 9(1) and 3(1) cm−1hc upon OH or OD stretch excitation. Comparisons are made with the more strongly asymmetric monoterpenols borneol and isopinocampheol as well as with the symmetric, rapidly tunneling propargyl alcohol. In addition, the third—in contrast localized—torsional conformer and the most stable dimer are assigned for α-fenchol, as well as the two most stable dimers for propargyl alcohol. ; Rotational microwave jet spectroscopy studies of the monoterpenol α-fenchol have so far failed to identify its second most stable torsional conformer, despite computational predictions that it is only very slightly higher in energy than the global minimum. Vibrational FTIR and Raman jet spectroscopy investigations reveal unusually complex OH and OD stretching spectra compared to other alcohols. Via modeling of the torsional states, observed spectral splittings are explained by delocalization of the hydroxy hydrogen atom through quantum tunneling between the two non-equivalent but accidentally near-degenerate conformers separated by a low and narrow barrier. The energy differences between the torsional states are determined to be only 16(1) and 7(1) cm−1hc for the protiated and deuterated ... |
| Document Type: |
article in journal/newspaper |
| Language: |
English |
| Relation: |
molecules27010101 |
| DOI: |
10.3390/molecules27010101 |
| Availability: |
https://resolver.sub.uni-goettingen.de/purl?gro-2/98959; https://doi.org/10.3390/molecules27010101 |
| Rights: |
info:eu-repo/semantics/openAccess ; Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). |
| Accession Number: |
edsbas.FD55C8A0 |
| Database: |
BASE |