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Magnetic Anisotropy of the C-C Single Bond

Authorized Users Only
2013
Authors
Baranac-Stojanović, Marija
Stojanović, Milovan
Article (Published version)
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Abstract
Anisotropic effects are broadly used in NMR spectroscopy for structure elucidation. With the development of computational methods it has become possible to quantify the effects and obtain further insight into their origin. Some classical interpretations have been questioned. Herein, we show that the classical "anisotropy cone" representing the anisotropic effect of the C-C single bond should be revised: deshielding at its side and shielding along its end are observed. Consequently, methyl, methylene, and methyne hydrogen atoms are not de-shielded by C-C bonds as is conventionally explained in NMR spectroscopy textbooks. They are just less shielded than by the C-H bonds attached at the same carbon. In addition, this anisotropic effect is dependent on the environment and care should be taken when drawing conclusions based on it. For example, it differs for the staggered and eclipsed conformations of ethane in HCCH planes, as well as for cyclohexane. In fact, it is not the anisotropy of t...he C2-C3/C5-C6 bonds that determines the chemical shift difference of axial and equatorial protons of a rigid cyclohexane ring, but magnetic contributions from all bonds.

Keywords:
anisotropic effects / C-C bond / cyclohexane / density functional calculations / NMR spectroscopy
Source:
Chemistry-A European Journal, 2013, 19, 13, 4249-4254
Publisher:
  • Wiley-V C H Verlag Gmbh, Weinheim
Funding / projects:
  • Experimental and theoretical study of reactivity and biological activity of stereodefined thiazolidines and their synthetic analogues (RS-172020)

DOI: 10.1002/chem.201204267

ISSN: 0947-6539

PubMed: 23400889

WoS: 000316623200020

Scopus: 2-s2.0-84875150144
[ Google Scholar ]
6
6
URI
https://cer.ihtm.bg.ac.rs/handle/123456789/1347
Collections
  • Radovi istraživača / Researchers' publications
Institution/Community
IHTM
TY  - JOUR
AU  - Baranac-Stojanović, Marija
AU  - Stojanović, Milovan
PY  - 2013
UR  - https://cer.ihtm.bg.ac.rs/handle/123456789/1347
AB  - Anisotropic effects are broadly used in NMR spectroscopy for structure elucidation. With the development of computational methods it has become possible to quantify the effects and obtain further insight into their origin. Some classical interpretations have been questioned. Herein, we show that the classical "anisotropy cone" representing the anisotropic effect of the C-C single bond should be revised: deshielding at its side and shielding along its end are observed. Consequently, methyl, methylene, and methyne hydrogen atoms are not de-shielded by C-C bonds as is conventionally explained in NMR spectroscopy textbooks. They are just less shielded than by the C-H bonds attached at the same carbon. In addition, this anisotropic effect is dependent on the environment and care should be taken when drawing conclusions based on it. For example, it differs for the staggered and eclipsed conformations of ethane in HCCH planes, as well as for cyclohexane. In fact, it is not the anisotropy of the C2-C3/C5-C6 bonds that determines the chemical shift difference of axial and equatorial protons of a rigid cyclohexane ring, but magnetic contributions from all bonds.
PB  - Wiley-V C H Verlag Gmbh, Weinheim
T2  - Chemistry-A European Journal
T1  - Magnetic Anisotropy of the C-C Single Bond
VL  - 19
IS  - 13
SP  - 4249
EP  - 4254
DO  - 10.1002/chem.201204267
ER  - 
@article{
author = "Baranac-Stojanović, Marija and Stojanović, Milovan",
year = "2013",
abstract = "Anisotropic effects are broadly used in NMR spectroscopy for structure elucidation. With the development of computational methods it has become possible to quantify the effects and obtain further insight into their origin. Some classical interpretations have been questioned. Herein, we show that the classical "anisotropy cone" representing the anisotropic effect of the C-C single bond should be revised: deshielding at its side and shielding along its end are observed. Consequently, methyl, methylene, and methyne hydrogen atoms are not de-shielded by C-C bonds as is conventionally explained in NMR spectroscopy textbooks. They are just less shielded than by the C-H bonds attached at the same carbon. In addition, this anisotropic effect is dependent on the environment and care should be taken when drawing conclusions based on it. For example, it differs for the staggered and eclipsed conformations of ethane in HCCH planes, as well as for cyclohexane. In fact, it is not the anisotropy of the C2-C3/C5-C6 bonds that determines the chemical shift difference of axial and equatorial protons of a rigid cyclohexane ring, but magnetic contributions from all bonds.",
publisher = "Wiley-V C H Verlag Gmbh, Weinheim",
journal = "Chemistry-A European Journal",
title = "Magnetic Anisotropy of the C-C Single Bond",
volume = "19",
number = "13",
pages = "4249-4254",
doi = "10.1002/chem.201204267"
}
Baranac-Stojanović, M.,& Stojanović, M.. (2013). Magnetic Anisotropy of the C-C Single Bond. in Chemistry-A European Journal
Wiley-V C H Verlag Gmbh, Weinheim., 19(13), 4249-4254.
https://doi.org/10.1002/chem.201204267
Baranac-Stojanović M, Stojanović M. Magnetic Anisotropy of the C-C Single Bond. in Chemistry-A European Journal. 2013;19(13):4249-4254.
doi:10.1002/chem.201204267 .
Baranac-Stojanović, Marija, Stojanović, Milovan, "Magnetic Anisotropy of the C-C Single Bond" in Chemistry-A European Journal, 19, no. 13 (2013):4249-4254,
https://doi.org/10.1002/chem.201204267 . .

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