Conformational Study of (R)-(−)-2,2,2-Trifluoro-1-(9-anthryl)ethanol (Pirkle’s Alcohol) by Dynamic NMR

Carlos Jaime; Albert Virgili; Rosa Maria Claramunt; Concepción López; José Elguero

doi:10.1021/jo00023a014

Conformational Study of (R)-(−)-2,2,2-Trifluoro-1-(9-anthryl)ethanol (Pirkle’s Alcohol) by Dynamic NMR

Carlos Jaime, Albert Virgili, Rosa Maria Claramunt, Concepción López, José Elguero

Department of Chemistry

Research output: Contribution to journal › Article › Research › peer-review

14 Citations (Scopus)

Abstract

Observation of anisochronous 1H and 13C NMR signals in (R)-(−)-2,2,2-trifluoro-1-(9-anthryl)ethanol at low temperature indicates that restricted rotation around the C(sp2)–C(sp3) bond occurs. From the coalescence temperature data and the corresponding chemical shift difference, the free energy of activation for rotation was evaluated to be 14.5 kcal mol−1 at 320 K in deuteriochloroform. These results, together with MM2 calculations, indicate that the ground-state conformation is that in which the trifluoromethyl group is almost orthogonal to the anthracene ring. The transition state will correspond then to the conformation in which the CF3 group eclipses the aromatic nucleus. Complete and 13C NMR assignments of the system at the frozen ground state (340 K) were made by homo- and heteronuclear COSY experiments and NOE difference spectroscopy. © 1991, American Chemical Society. All rights reserved.

Original language	English
Pages (from-to)	6521-6523
Journal	Journal of Organic Chemistry
Volume	56
Issue number	23
DOIs	https://doi.org/10.1021/jo00023a014
Publication status	Published - 1 Nov 1991

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@article{cdb179b979ac4be4b347e94d36809c79,

title = "Conformational Study of (R)-(−)-2,2,2-Trifluoro-1-(9-anthryl)ethanol (Pirkle{\textquoteright}s Alcohol) by Dynamic NMR",

abstract = "Observation of anisochronous 1H and 13C NMR signals in (R)-(−)-2,2,2-trifluoro-1-(9-anthryl)ethanol at low temperature indicates that restricted rotation around the C(sp2)–C(sp3) bond occurs. From the coalescence temperature data and the corresponding chemical shift difference, the free energy of activation for rotation was evaluated to be 14.5 kcal mol−1 at 320 K in deuteriochloroform. These results, together with MM2 calculations, indicate that the ground-state conformation is that in which the trifluoromethyl group is almost orthogonal to the anthracene ring. The transition state will correspond then to the conformation in which the CF3 group eclipses the aromatic nucleus. Complete and 13C NMR assignments of the system at the frozen ground state (340 K) were made by homo- and heteronuclear COSY experiments and NOE difference spectroscopy. {\textcopyright} 1991, American Chemical Society. All rights reserved.",

author = "Carlos Jaime and Albert Virgili and Claramunt, {Rosa Maria} and Concepci{\'o}n L{\'o}pez and Jos{\'e} Elguero",

year = "1991",

month = nov,

day = "1",

doi = "10.1021/jo00023a014",

language = "English",

volume = "56",

pages = "6521--6523",

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T1 - Conformational Study of (R)-(−)-2,2,2-Trifluoro-1-(9-anthryl)ethanol (Pirkle’s Alcohol) by Dynamic NMR

AU - Jaime, Carlos

AU - Virgili, Albert

AU - Claramunt, Rosa Maria

AU - López, Concepción

AU - Elguero, José

PY - 1991/11/1

Y1 - 1991/11/1

N2 - Observation of anisochronous 1H and 13C NMR signals in (R)-(−)-2,2,2-trifluoro-1-(9-anthryl)ethanol at low temperature indicates that restricted rotation around the C(sp2)–C(sp3) bond occurs. From the coalescence temperature data and the corresponding chemical shift difference, the free energy of activation for rotation was evaluated to be 14.5 kcal mol−1 at 320 K in deuteriochloroform. These results, together with MM2 calculations, indicate that the ground-state conformation is that in which the trifluoromethyl group is almost orthogonal to the anthracene ring. The transition state will correspond then to the conformation in which the CF3 group eclipses the aromatic nucleus. Complete and 13C NMR assignments of the system at the frozen ground state (340 K) were made by homo- and heteronuclear COSY experiments and NOE difference spectroscopy. © 1991, American Chemical Society. All rights reserved.

AB - Observation of anisochronous 1H and 13C NMR signals in (R)-(−)-2,2,2-trifluoro-1-(9-anthryl)ethanol at low temperature indicates that restricted rotation around the C(sp2)–C(sp3) bond occurs. From the coalescence temperature data and the corresponding chemical shift difference, the free energy of activation for rotation was evaluated to be 14.5 kcal mol−1 at 320 K in deuteriochloroform. These results, together with MM2 calculations, indicate that the ground-state conformation is that in which the trifluoromethyl group is almost orthogonal to the anthracene ring. The transition state will correspond then to the conformation in which the CF3 group eclipses the aromatic nucleus. Complete and 13C NMR assignments of the system at the frozen ground state (340 K) were made by homo- and heteronuclear COSY experiments and NOE difference spectroscopy. © 1991, American Chemical Society. All rights reserved.

U2 - 10.1021/jo00023a014

DO - 10.1021/jo00023a014

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