H-1 NMR Chemical Shifts of Cyclopropane and Cyclobutane: A Theoretical Study
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2013
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This study was undertaken in order to rationalize the peculiar H-1 NMR chemical shifts of cyclopropane (delta 0.22) and cyclobutane (delta 1.98) which are shifted upfield and downfield with respect to larger cycloalkanes (delta 1.44-1.54). This is conventionally accounted for by shielding contributions arising from an aromatic-like ring current in cyclopropane, involving six electrons in the three C-C bonds, and deshielding coming from the sigma antiaromatic CC framework of cyclobutane. The shielding pattern arising from the cyclopropane and cyclobutane CC framework response to a perpendicular magnetic field was visualized as two-dimensional grid distribution of NICS values. Further insight into the origin of chemical shift values was obtained by the NCS-NBO analysis of proton shielding tensor. In the case of cyclopropane, the CC framework shielding pattern implies the existence of both delocalized and localized currents that have a dominant shielding effect on protons. The magnitude o...f C-H bonds shielding effect is significant, too. Unlike the conventional interpretation, the CC framework shields cyclobutane hydrogens, and its response to a perpendicular magnetic field is quite similar to responses of other planar sigma CC frameworks.
Izvor:
Journal of Organic Chemistry, 2013, 78, 4, 1504-1507Izdavač:
- American Chemical Society (ACS)
Finansiranje / projekti:
DOI: 10.1021/jo3025863
ISSN: 0022-3263
PubMed: 23330566
WoS: 000315254100019
Scopus: 2-s2.0-84873955750
Institucija/grupa
IHTMTY - JOUR AU - Baranac-Stojanović, Marija AU - Stojanović, Milovan PY - 2013 UR - https://cer.ihtm.bg.ac.rs/handle/123456789/1284 AB - This study was undertaken in order to rationalize the peculiar H-1 NMR chemical shifts of cyclopropane (delta 0.22) and cyclobutane (delta 1.98) which are shifted upfield and downfield with respect to larger cycloalkanes (delta 1.44-1.54). This is conventionally accounted for by shielding contributions arising from an aromatic-like ring current in cyclopropane, involving six electrons in the three C-C bonds, and deshielding coming from the sigma antiaromatic CC framework of cyclobutane. The shielding pattern arising from the cyclopropane and cyclobutane CC framework response to a perpendicular magnetic field was visualized as two-dimensional grid distribution of NICS values. Further insight into the origin of chemical shift values was obtained by the NCS-NBO analysis of proton shielding tensor. In the case of cyclopropane, the CC framework shielding pattern implies the existence of both delocalized and localized currents that have a dominant shielding effect on protons. The magnitude of C-H bonds shielding effect is significant, too. Unlike the conventional interpretation, the CC framework shields cyclobutane hydrogens, and its response to a perpendicular magnetic field is quite similar to responses of other planar sigma CC frameworks. PB - American Chemical Society (ACS) T2 - Journal of Organic Chemistry T1 - H-1 NMR Chemical Shifts of Cyclopropane and Cyclobutane: A Theoretical Study VL - 78 IS - 4 SP - 1504 EP - 1507 DO - 10.1021/jo3025863 ER -
@article{ author = "Baranac-Stojanović, Marija and Stojanović, Milovan", year = "2013", abstract = "This study was undertaken in order to rationalize the peculiar H-1 NMR chemical shifts of cyclopropane (delta 0.22) and cyclobutane (delta 1.98) which are shifted upfield and downfield with respect to larger cycloalkanes (delta 1.44-1.54). This is conventionally accounted for by shielding contributions arising from an aromatic-like ring current in cyclopropane, involving six electrons in the three C-C bonds, and deshielding coming from the sigma antiaromatic CC framework of cyclobutane. The shielding pattern arising from the cyclopropane and cyclobutane CC framework response to a perpendicular magnetic field was visualized as two-dimensional grid distribution of NICS values. Further insight into the origin of chemical shift values was obtained by the NCS-NBO analysis of proton shielding tensor. In the case of cyclopropane, the CC framework shielding pattern implies the existence of both delocalized and localized currents that have a dominant shielding effect on protons. The magnitude of C-H bonds shielding effect is significant, too. Unlike the conventional interpretation, the CC framework shields cyclobutane hydrogens, and its response to a perpendicular magnetic field is quite similar to responses of other planar sigma CC frameworks.", publisher = "American Chemical Society (ACS)", journal = "Journal of Organic Chemistry", title = "H-1 NMR Chemical Shifts of Cyclopropane and Cyclobutane: A Theoretical Study", volume = "78", number = "4", pages = "1504-1507", doi = "10.1021/jo3025863" }
Baranac-Stojanović, M.,& Stojanović, M.. (2013). H-1 NMR Chemical Shifts of Cyclopropane and Cyclobutane: A Theoretical Study. in Journal of Organic Chemistry American Chemical Society (ACS)., 78(4), 1504-1507. https://doi.org/10.1021/jo3025863
Baranac-Stojanović M, Stojanović M. H-1 NMR Chemical Shifts of Cyclopropane and Cyclobutane: A Theoretical Study. in Journal of Organic Chemistry. 2013;78(4):1504-1507. doi:10.1021/jo3025863 .
Baranac-Stojanović, Marija, Stojanović, Milovan, "H-1 NMR Chemical Shifts of Cyclopropane and Cyclobutane: A Theoretical Study" in Journal of Organic Chemistry, 78, no. 4 (2013):1504-1507, https://doi.org/10.1021/jo3025863 . .