Fluorine-decoupled carbon spectroscopy for the determination of configuration at fully substituted, trifluoromethyl- and perfluoroalkyl-bearing carbons: comparison with 19F-1H heteronuclear Overhauser effect spectroscopy (original) (raw)

The conjunction of aromaticity and hypervalency: the C5H5SF3 molecule 1,1,1-trifluorothiabenzene

Journal of Molecular Structure: THEOCHEM, 1991

Ab initio quantum mechanical methods have been applied to the molecule formed via the intimate union of benzene and sulfur hexafluoride. The self-consistent-field (SCF) method has been used with a full double zeta (DZ) basis extended by a set of d functions on sulfur and also with the DZ basis extended by polarization functions on all atoms (DZ+ P). The stationary point geometries of two structures, both of C, symmetry, have been determined theoretically. In Structure C, I the two C-S bonds are equivalent, and in Structure C, II the C&H&l skeleton is coplanar. At the DZ+ d (S) SCF and DZ+P SCF levels of theory, Structure I is a transition state, lying 2.1 and 3.4 kcal mol-i, respectively, above Structure II which is a true minimum. Structure I is distinctly aromatic, Structure II has some aromatic characteristics, and it is argued that the effective structure of l,l,l-trifluorothiabenzene is likely to be a superposition of Structures I and II. These results are easily explained with the concepts of directional repulsion effects of x bonds, apicophilicity of substituent groups in trigonal bipyramidal systems, and Bent's rule. Comparisons of the calculated structures are made with benzene, sulfur hexafluoride, CH2=SF4, and CH,-SF,. The predicted vibrational frequencies and infrared intensities may be helpful in the eventual identification of l,l,l-trifluorothiabenzene.

Fluorofluoroxydioxirane and Other CF 2 O 3 Isomers

The Journal of Physical Chemistry A, 2001

Seven structural isomers, and relevant transition states, on the lowest-energy spin-singlet potential energy surface of CF 2 O 3 are characterized using correlated ab initio electronic structure methods. On the basis of preliminary comparative calculations, second-order Møller-Plesset perturbation theory with a correlationconsistent polarized valence double-one-electron basis set (MP2/cc-pVDZ) was chosen with which to describe equilibrium structures and harmonic vibrational frequencies of all relevant rotamers. Accurate energy differences were determined using the coupled cluster method, with perturbative inclusion of triple excitations, and a valence triple-basis (CCSD(T)/cc-pVTZ). The lowest energy isomer is predicted to be the molozonide of difluorocarbene, whose adiabatic decay is prevented by a sizable barrier. Plausible mechanisms for the isomerization of the titled compound to the low-energy fluoroformyl peroxyhypofluorite and nearly isenergetic carbonyl hypofluorite are suggested. An analogous reaction path may be of importance to the isomerization of difluorodioxirane (CF 2 O 2 ) and is included in the study.

Carbon-13-fluorine-19 coupling constants in benzotrifluorides

Organic Magnetic Resonance, 1977

The carbon-fluorine coupling constants in 33 ditierent substituted benzouifluorides (trifluoromethylbenzenes) have been determined. The 'J(CF) to the ortho aromatic ring carbons varied between 1.7 and 5.6Hz and, in a given molecule, were always larger than the 'J(CF) to the para carbon, which ranged between 0.7 and 1.7 Hz. Coupling to the ineta carbons, 'J(CF), was not observed and is under 0.3 Hz.

Synthesis and X-ray or NMR/DFT structure elucidation of twenty-one new trifluoromethyl derivatives of soluble cage isomers of C76, C78, C84, and C90

Journal of The American Chemical Society, 2008

Adding 1% of the metallic elements cerium, lanthanum, and yttrium to graphite rod electrodes resulted in different amounts of the hollow higher fullerenes (HHFs) C 76-D2(1), C78-C2v(2), and C78-C2v in carbon-arc fullerene-containing soots. The reaction of trifluoroiodomethane with these and other soluble HHFs at 520-550°C produced 21 new C 76,78,84,90(CF3

Fluorinated cyclohexanes: Synthesis of amine building blocks of the all-cis 2,3,5,6-tetrafluorocyclohexylamine motif

Beilstein Journal of Organic Chemistry, 2017

This paper reports the synthesis of three amine stereoisomers 5a–c of the tetrafluorocyclohexyl ring system, as building blocks for discovery chemistry programmes. The synthesis starts from a Birch reduction of benzonitrile, followed by an in situ methyl iodide quench. The resultant 2,5-cyclohexadiene was progressed via double epoxidations and then hydrofluorination ring opening reactions. The resultant fluorohydrin moieties were then converted to different stereoisomers of the tetrafluorocyclohexyl ring system, and then reductive hydrogenation of the nitrile delivered three amine stereoisomers. It proved necessary to place a methyl group on the cyclohexane ring in order to stabilise the compound against subsequent HF elimination. The two all-cis tetrafluorocyclohexyl isomers 5a and 5b constitute facially polarized cyclohexane rings, with fluorines on the electronegative face and hydrogens on the electropositive face.