91597-81-8Relevant articles and documents
Long-range coupling constants for α-13C nuclei in phenyl-X-R (X = O,S,Se,Te) derivatives. Internal rotational information
Schaefer, Ted,Penner, Glenn H.
, p. 1641 - 1646 (2007/10/02)
The longrange spin-spin coupling constant over six bonds between the 19F nucleus and the 13C nucleus in the side chain, 6J(C,F), is reported for 4-F-C6H4-X-R, where X = O, S and R = CH3,CH2CH3,CH(CH3) and C(CH3)3. 6J(C,F) depends on sin2θ, where θ is the angle by which the side chain twists out-of-plane about the Csp2-X bond.Exceptation values of sin2θ are obtained from 6J(C,F), yielding magnitudes of the apparent twofold barrier to rotation about the Csp2-X bond.In these terms, the most stable conformation is that for θ = 0 deg for all compounds, with the exception of R =C(CH3)3 and of X = S, R = CH(CH3)2; there is effectively free rotation about the Csp2-S bond is isopropyl 4-fluorophenyl sulfide in acetone-d6 solution.Good correlations exist between 6J(C,F) and a number of other molecular properties, including certain differences of ionization potentials of the molecular orbitals in the ether.In particular, the chemical shifts of C-4 are correlated with 6J(C,F).Because 5J(C,C), the coupling constant involving C-4, also depends on sin2θ, it is measured for the methyl and ethyl selenides and tellurides, as are other 13C,13C couplings involving a 13C nucleus in the side chain.The literature values for the 13C nuclear magnetic resonance chemical shifts in alkyl phenyl selenides and tellurides can be related to θ preferences and also allow estimates of the extrema in 5j(C,C).The resultant values of arcsin 2θ>1'2 for R=CH3 are is good agreement with estimates of θ obtained from electron diffraction patterns, photoelectron spectra, and nuclear magnetic resonance in the nematic phase.
