Fluorine molecular orbital model

The Effect of Fluorination on Polyacetylene and the Role of Internal Hydrogen Bonds to Fluorine Molecular Orbital Models... 

We report results of first-principles molecular orbital calculations on model clusters of graphite (C24), alkali graphite intercalation compounds (MC48 M = Li, Na, K, Rb, Cs), fullerene (Ceo), and fluorinated fullerenes (CeoFa, x — 18, 36, 48). The calculated partial densities of states (pDOS) are compared with measured x-ray absorption near edge structure (XANES) spectra, x-ray photoelectron spectra (XPS), x-ray emission spectra (XES), and ultraviolet photoelectron spectra (UPS). In the case of graphite and its compounds, the calculated pDOS well reproduce features of the observed XANES and UPS spectra. The calculated pDOS and the observed XPS, UPS and XANES of CeoFx (x = 0, 36, 48) are also in satisfactory accordance. 

Molecular orbital calculations on fluorinated butadienes and hexatrienes were used to model the effects of fluorination on the properties of poly(acetylene). Like poly(acetylene), "head-to-head" poly(fluoro- acetylene), (-CH=CF-CF=CH-), is predicted to adopt a planar, all trans structure, but poly(difluoro-acetylene) favors a non-planar skewed chain conformation. "Head-to-tail" poly(fluoroacetylene), (-CH=CF-CH=CF-) is predicted to favor a nearly planar cis structure stabilized by intramolecular CF-HC hydrogen binding. Calculations on 2-fluoroethanol and on both 2-fluoroacetaldehyde enol and its alkali metal (Li, Na, K) enolates reveal moderately strong intramolecular CF—HO hydrogen bonds(1.9 and 3.2 kcal/mol, respectively) and even stronger intramolecular coordination of CF to alkali metal cations (9-12 kcal/mol). 

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