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Conformational properties of 1-cyano-1-silacyclohexane, C5H10SiHCN: Gas electron diffraction, low-temperature NMR and quantum chemical calculations

Conformational properties of 1-cyano-1-silacyclohexane, C5H10SiHCN: Gas electron diffraction, low-temperature NMR and quantum chemical calculations


Titill: Conformational properties of 1-cyano-1-silacyclohexane, C5H10SiHCN: Gas electron diffraction, low-temperature NMR and quantum chemical calculations
Höfundur: Belyakov, Alexander V.
Sigolaev, Yrii F.
Shlykov, Sergey A.
Wallevik, Sunna Ó.
Jónsdóttir, Nanna R.
Jónsdóttir, Sigríður
Kvaran, Agust   orcid.org/0000-0002-1742-6994
Bjornsson, Ragnar   orcid.org/0000-0003-2167-8374
Árnason, Ingvar
Útgáfa: 2017-03
Tungumál: Enska
Umfang: 149-156
Háskóli/Stofnun: Háskóli Íslands
University of Iceland
Svið: Verkfræði- og náttúruvísindasvið (HÍ)
School of Engineering and Natural Sciences (UI)
Deild: Raunvísindastofnun (HÍ)
Science Institute (UI)
Birtist í: Journal of Molecular Structure;1132
ISSN: 0022-2860
DOI: 10.1016/j.molstruc.2016.10.012
Efnisorð: Silacyclohexane; Molecular structure; Gas electron diffraction; Dynamic NMR spectroscopy; Quantum chemical calculations; Conformational analysis; Spectroscopy; Sameindir; Rafeindir; Ólífræn efnafræði
URI: https://hdl.handle.net/20.500.11815/547

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Tilvitnun:

Belyakov, A. V., Sigolaev, Y. F., Shlykov, S. A., Wallevik, S. Ó., Jonsdottir, N. R., Jonsdottir, S., . . . Arnason, I. (2017). Conformational properties of 1-cyano-1-silacyclohexane, C5H10SiHCN: Gas electron diffraction, low-temperature NMR and quantum chemical calculations. Journal of Molecular Structure, 1132, 149-156. doi:https://doi.org/10.1016/j.molstruc.2016.10.012

Útdráttur:

The conformational preference of the cyano group of the 1-cyano-1-silacyclohexane was studied experimentally by means of gas electron diffraction (GED) and dynamic nuclear magnetic resonance (DNMR) as well as by quantum chemical (QC) calculations applying high-level coupled cluster methods as well as DFT methods. According to the GED experiment, the compound exists in the gas-phase as a mixture of two conformers possessing the chair conformation of the six-membered ring and Cs symmetry while differing in the axial or equatorial position of the substituent (axial = 84(12) mol %/equatorial = 16(12) mol %) at T = 279(3) K, corresponding to an A value (Gax – Geq) of −1.0(4) kcal mol−1. Gas-phase CCSD(T) calculations predict an A value of −0.72 kcal mol−1 at 279 K. In contrast, the low-temperature 13C NMR experiments resulted in an axial/equatorial ratio of 35/65 mol % at 120 K corresponding to an A value of 0.14 kcal mol−1. An average value for ΔG#e→a = 5.6 ± 0.1 kcal mol−1 was obtained for the temperature range 110–145 K. The dramatically different conformational behaviour in the gas-phase (GED) compared to the liquid phase (DNMR) suggests a strong solvation effect. According to natural bond orbital analysis the axial conformer of the title compound is an example of stabilization of a form, which is not favored by electrostatic effects and is favored predominantly by steric and conjugation effects.

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© 2016 Elsevier B.V. All rights reserved.

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