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NMR spectroscopy investigation of the cooperative nature of the internal rotational motions in acetophenone

NMR spectroscopy investigation of the cooperative nature of the internal rotational motions in acetophenone
NMR spectroscopy investigation of the cooperative nature of the internal rotational motions in acetophenone

The proton NMR spectrum of the doubly enriched acetophenone-carbonyl, methyl-13C2 isotopomer dissolved in a liquid-crystalline solvent (LXNMR) was analyzed to yield a data set of 19 dipolar couplings. The presence of so many couplings, and in particular the dependence of some of them on the acetyl carbons enabled the investigation of the structure of the acetyl moiety and of possible cooperative motions about the aryl-carbonyl and carbonyl-methyl bonds. Methodological aspects, and approximations relating to the application of the vibrational correction procedure in the presence of large-amplitude torsional motions, are discussed. Results show that it is possible to discriminate between a continuous and a discrete conformer distribution about the angle φ1 but not among a few proposed continuous shapes of Uiso({φ}). In this study, the use of dipolar couplings with a non-negligible contribution from the indirect spin-spin coupling tensor J, (DC8C9 in our case), for structural determination is extended from rigid to flexible molecules. The 1/2JC8C9 aniso contribution was derived theoretically using the density functional theory linear response (DFT-LR) first-principles calculation of the JC8C9 spin-spin coupling tensor.

Conformational analysis, Density functional calculations, Indirect coupling anisotropy, Liquid crystals, NMR spectroscopy
1439-4235
2086-2098
De Luca, Giuseppina
8152f554-4aa6-42bf-af23-c0d74db9f69e
Longeri, Marcello
3b1f11d6-2c93-4221-898b-b85385f0b0ed
Pileio, Giuseppe
13f78e66-0707-4438-b9c9-6dbd3eb7d4e8
Lantto, Perttu
36f9c57b-3d28-4e5d-949e-947d25112cc6
De Luca, Giuseppina
8152f554-4aa6-42bf-af23-c0d74db9f69e
Longeri, Marcello
3b1f11d6-2c93-4221-898b-b85385f0b0ed
Pileio, Giuseppe
13f78e66-0707-4438-b9c9-6dbd3eb7d4e8
Lantto, Perttu
36f9c57b-3d28-4e5d-949e-947d25112cc6

De Luca, Giuseppina, Longeri, Marcello, Pileio, Giuseppe and Lantto, Perttu (2005) NMR spectroscopy investigation of the cooperative nature of the internal rotational motions in acetophenone. ChemPhysChem, 6 (10), 2086-2098. (doi:10.1002/cphc.200500134).

Record type: Article

Abstract

The proton NMR spectrum of the doubly enriched acetophenone-carbonyl, methyl-13C2 isotopomer dissolved in a liquid-crystalline solvent (LXNMR) was analyzed to yield a data set of 19 dipolar couplings. The presence of so many couplings, and in particular the dependence of some of them on the acetyl carbons enabled the investigation of the structure of the acetyl moiety and of possible cooperative motions about the aryl-carbonyl and carbonyl-methyl bonds. Methodological aspects, and approximations relating to the application of the vibrational correction procedure in the presence of large-amplitude torsional motions, are discussed. Results show that it is possible to discriminate between a continuous and a discrete conformer distribution about the angle φ1 but not among a few proposed continuous shapes of Uiso({φ}). In this study, the use of dipolar couplings with a non-negligible contribution from the indirect spin-spin coupling tensor J, (DC8C9 in our case), for structural determination is extended from rigid to flexible molecules. The 1/2JC8C9 aniso contribution was derived theoretically using the density functional theory linear response (DFT-LR) first-principles calculation of the JC8C9 spin-spin coupling tensor.

Full text not available from this repository.

More information

Published date: October 2005
Keywords: Conformational analysis, Density functional calculations, Indirect coupling anisotropy, Liquid crystals, NMR spectroscopy

Identifiers

Local EPrints ID: 414789
URI: https://eprints.soton.ac.uk/id/eprint/414789
ISSN: 1439-4235
PURE UUID: 1dd97cb6-238e-410a-ac10-dd95ad746347
ORCID for Giuseppe Pileio: ORCID iD orcid.org/0000-0001-9223-3896

Catalogue record

Date deposited: 11 Oct 2017 16:31
Last modified: 14 Mar 2019 01:42

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