Effect of fluorination on methyl internal rotation barriers: Microwave spectra of cyclopropylfluoromethyl silane (c-C3H5SiHFCH3) and cyclopropyldifluoromethyl silane (c-C3H5SiF2CH3)

Dorris, Rachel E.; Luce, Bailey C.; Stettner, Sarah J.; Peebles, Rebecca A.; Peebles, Sean A.; Bullard, John L.; Bunn, James E.; Guirgis, Gamil A.

doi:10.1016/j.jms.2015.10.001

Cited by 2 publications

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“…Methyl rotor internal rotation is a topic that has been heavily studied for over 60 years. − Over the past 45+ years, the molecular structure and internal rotation dynamics of species with one or two −SiH 3 groups have been of significant interest. ,,− This interest and area of study has been significantly driven from the differences in molecular structure upon substitution of a carbon atom by a silicon atom. The general elongation of the bond created from the Si substitution lowers torsional energy strain, providing more freedom for the −SiH 3 group to rotate.…”

Section: Introductionmentioning

confidence: 99%

The Conformational Landscape, Internal Rotation, and Structure of 1,3,5-Trisilapentane using Broadband Rotational Spectroscopy and Quantum Chemical Calculations

et al. 2020

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The rotational spectrum of 1,3,5-trisilapentane was observed on a chirped-pulse Fourier transform microwave spectrometer and is reported. During assignment, multiple conformations of the molecule were identified in the molecular beam. Prior quantum-chemical calculations performed on the molecule show that the identified spectra correspond to the lowest three calculated energetic structures. These structures are of C 2 (Conf.1), C 2v (Conf.2), and C 1 (Conf.3) symmetry, with relative energy ordering of Conf.1 < Conf.3 < Conf.2, which is in stark contrast to n-pentane and all known silicon-substituted n-pentane derivatives. This is found to most likely arise from the elongation of the Si−C bond and the size of the silicon atoms providing for the C 2 and C 1 structures relieving steric hindrance in comparison to that of the C 2v . In the C 2v and C 1 conformers, splitting in the spectra due to internal rotation of the −SiH 3 end groups of 1,3,5-trisilapentane was observed and determined. The C 2v equivalent V 3 values are 368.46(33) cm −1 , and the C 1 V 3 values are 347.78(21) and 360.18(88) cm −1 , respectively. These barriers are compared to similar species in order to help verify their veracity and are determined to be accurate based on similar molecular silyl rotors.

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Section: Introductionmentioning

confidence: 99%

The Conformational Landscape, Internal Rotation, and Structure of 1,3,5-Trisilapentane using Broadband Rotational Spectroscopy and Quantum Chemical Calculations

et al. 2020

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Rotational spectrum, structure, and quadrupole coupling of cyclopropylchloromethyldifluorosilane

Davies,

Hanna,

Lutas

et al. 2024

The Journal of Chemical Physics

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Cyclopropylchloromethyldifluorosilane, c-C3H5SiF2CH2Cl, has been synthesized, and its rotational spectrum has been recorded by chirped-pulse Fourier transform microwave spectroscopy. The spectral analysis of several isotopologues indicates the presence of two distinct conformations in the free-jet expansion, which are interconvertible through a rotation of the chloromethyl group. A partial substitution structure is presented for the lower energy conformation and is compared to the equilibrium structure obtained from quantum chemical calculations. Additionally, the presence of the chlorine nucleus leads to the rotational transitions splitting into multiple hyperfine components and χaa, a measure of the electric field gradient along the a axis, is unusually small at merely +0.1393(73) MHz. Various common ab initio and density functional theory methods fail to predict good quadrupole coupling constants (in the principal axis system) that adequately reproduce the observed hyperfine splitting, although diagonalizing the quadrupole coupling tensor from the principal axis system into a nucleus-centered axis system reveals that, overall, these methods calculate reasonably the electric field gradient about the chlorine nucleus. Finally, a total of nine electric dipole forbidden, quadrupole allowed transitions are observed in the rotational spectra of the parent species of the higher energy conformation and the 37Cl isotopologue of the lower energy conformation. These include those of x-type (no change in parity of Ka or Kc), which, to our knowledge, is the first time such transitions have been observed in a chlorine-containing molecule.

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Effect of fluorination on methyl internal rotation barriers: Microwave spectra of cyclopropylfluoromethyl silane (c-C3H5SiHFCH3) and cyclopropyldifluoromethyl silane (c-C3H5SiF2CH3)

Cited by 2 publications

References 21 publications

The Conformational Landscape, Internal Rotation, and Structure of 1,3,5-Trisilapentane using Broadband Rotational Spectroscopy and Quantum Chemical Calculations

The Conformational Landscape, Internal Rotation, and Structure of 1,3,5-Trisilapentane using Broadband Rotational Spectroscopy and Quantum Chemical Calculations

Rotational spectrum, structure, and quadrupole coupling of cyclopropylchloromethyldifluorosilane

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