Nonclassical dynamics of the methyl group in 1,1,1-triphenylethane. Evidence from powder 1H NMR spectra

Handle URI:
http://hdl.handle.net/10754/623041
Title:
Nonclassical dynamics of the methyl group in 1,1,1-triphenylethane. Evidence from powder 1H NMR spectra
Authors:
Osior, Agnieszka; Kalicki, Przemysław; Kamieński, Bohdan; Szymański, Sławomir; Bernatowicz, Piotr; Shkurenko, Aleksander ( 0000-0001-7136-2277 )
Abstract:
According to the damped quantum rotation (DQR) theory, hindered rotation of methyl groups, evidenced in nuclear magnetic resonance (NMR) line shapes, is a nonclassical process. It comprises a number of quantum-rate processes measured by two different quantum-rate constants. The classical jump model employing only one rate constant is reproduced if these quantum constants happen to be equal. The values of their ratio, or the nonclassicallity coefficient, determined hitherto from NMR spectra of single crystals and solutions range from about 1.20 to 1.30 in the latter case to above 5.0 in the former, with the value of 1 corresponding to the jump model. Presently, first systematic investigations of the DQR effects in wide-line NMR spectra of a powder sample are reported. For 1,1,1-triphenylethane deuterated in the aromatic positions, the relevant line-shape effects were monitored in the range 99–121 K. The values of the nonclassicality coefficient dropping from 2.7 to 1.7 were evaluated in line shape fits to the experimental powder spectra from the range 99–108 K. At these temperatures, the fits with the conventional line-shape model are visibly inferior to the DQR fits. Using a theoretical model reported earlier, a semiquantitative interpretation of the DQR parameters evaluated from the spectra is given. It is shown that the DQR effects as such can be detected in wide-line NMR spectra of powdered samples, which are relatively facile to measure. However, a fully quantitative picture of these effects can only be obtained from the much more demanding experiments on single crystals.
KAUST Department:
Advanced Membranes and Porous Materials Research Center; Functional Materials Design, Discovery and Development (FMD3); Physical Sciences and Engineering (PSE) Division
Citation:
Osior A, Kalicki P, Kamieński B, Szymański S, Bernatowicz P, et al. (2017) Nonclassical dynamics of the methyl group in 1,1,1-triphenylethane. Evidence from powder 1H NMR spectra. The Journal of Chemical Physics 146: 104504. Available: http://dx.doi.org/10.1063/1.4978226.
Publisher:
AIP Publishing
Journal:
The Journal of Chemical Physics
Issue Date:
14-Mar-2017
DOI:
10.1063/1.4978226
Type:
Article
ISSN:
0021-9606; 1089-7690
Sponsors:
P.B., A.O., and S.S. acknowledge partial financial support of this work by the National Center of Science (NCN Grant No. 2012/05/B/ST4/00103).
Additional Links:
http://aip.scitation.org/doi/10.1063/1.4978226
Appears in Collections:
Articles; Advanced Membranes and Porous Materials Research Center; Physical Sciences and Engineering (PSE) Division; Functional Materials Design, Discovery and Development (FMD3)

Full metadata record

DC FieldValue Language
dc.contributor.authorOsior, Agnieszkaen
dc.contributor.authorKalicki, Przemysławen
dc.contributor.authorKamieński, Bohdanen
dc.contributor.authorSzymański, Sławomiren
dc.contributor.authorBernatowicz, Piotren
dc.contributor.authorShkurenko, Aleksanderen
dc.date.accessioned2017-03-20T08:46:09Z-
dc.date.available2017-03-20T08:46:09Z-
dc.date.issued2017-03-14en
dc.identifier.citationOsior A, Kalicki P, Kamieński B, Szymański S, Bernatowicz P, et al. (2017) Nonclassical dynamics of the methyl group in 1,1,1-triphenylethane. Evidence from powder 1H NMR spectra. The Journal of Chemical Physics 146: 104504. Available: http://dx.doi.org/10.1063/1.4978226.en
dc.identifier.issn0021-9606en
dc.identifier.issn1089-7690en
dc.identifier.doi10.1063/1.4978226en
dc.identifier.urihttp://hdl.handle.net/10754/623041-
dc.description.abstractAccording to the damped quantum rotation (DQR) theory, hindered rotation of methyl groups, evidenced in nuclear magnetic resonance (NMR) line shapes, is a nonclassical process. It comprises a number of quantum-rate processes measured by two different quantum-rate constants. The classical jump model employing only one rate constant is reproduced if these quantum constants happen to be equal. The values of their ratio, or the nonclassicallity coefficient, determined hitherto from NMR spectra of single crystals and solutions range from about 1.20 to 1.30 in the latter case to above 5.0 in the former, with the value of 1 corresponding to the jump model. Presently, first systematic investigations of the DQR effects in wide-line NMR spectra of a powder sample are reported. For 1,1,1-triphenylethane deuterated in the aromatic positions, the relevant line-shape effects were monitored in the range 99–121 K. The values of the nonclassicality coefficient dropping from 2.7 to 1.7 were evaluated in line shape fits to the experimental powder spectra from the range 99–108 K. At these temperatures, the fits with the conventional line-shape model are visibly inferior to the DQR fits. Using a theoretical model reported earlier, a semiquantitative interpretation of the DQR parameters evaluated from the spectra is given. It is shown that the DQR effects as such can be detected in wide-line NMR spectra of powdered samples, which are relatively facile to measure. However, a fully quantitative picture of these effects can only be obtained from the much more demanding experiments on single crystals.en
dc.description.sponsorshipP.B., A.O., and S.S. acknowledge partial financial support of this work by the National Center of Science (NCN Grant No. 2012/05/B/ST4/00103).en
dc.publisherAIP Publishingen
dc.relation.urlhttp://aip.scitation.org/doi/10.1063/1.4978226en
dc.rightsThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in The Journal of Chemical Physics and may be found at http://doi.org/10.1063/1.4978226.en
dc.titleNonclassical dynamics of the methyl group in 1,1,1-triphenylethane. Evidence from powder 1H NMR spectraen
dc.typeArticleen
dc.contributor.departmentAdvanced Membranes and Porous Materials Research Centeren
dc.contributor.departmentFunctional Materials Design, Discovery and Development (FMD3)en
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalThe Journal of Chemical Physicsen
dc.eprint.versionPublisher's Version/PDFen
dc.contributor.institutionInstitute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warszawa, Polanden
dc.contributor.institutionInstitute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warszawa, Polanen
kaust.authorShkurenko, Aleksanderen
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