Elektronenbeugungsbestimmung der Molekülstruktur von 4-Fluor-2′,4′,6′ -trimethylbiphenyl / Molecular Structure of 4-Fluoro-2′,4′,6′-trimethylbiphenyl Determined by Electron Diffraction

Abstract

The molecular structure of gaseous 4-fluoro-2′,4′,6′-trimethylbiphenyl was determined by electron diffraction. The average of two independend determinations leads to the following parameters for the structure: CC(ring) = 1.398(1),CC(methyl) = 1.522(5), CH(ring) = 1.082(6), CH(methyl) = CH(ring) + 0.015 = 1.097(6), CF = 1.324(7), Cl-Cl′ = 1.488(9) (inter ring bond), ∢(C,C,H) = 109.9(1.8)° (angle of methylgroup tetrahedra), α = 124.9(0.6)° (angle of ortho-methyl-groups towards the inter ring bond), φ = 77.5(2.1)° (angle of torsion between the planes of the two phenyl rings) which are in good agreement with respect to known structural data on biphenylderivatives. A very interesting result is the angle of torsion with 77.5° which is by 6.5° smaller than the value of 84(1)° determined by X-ray crystallography for the corresponding 4-iodo-compound in the crystalline state1. In all determinations known to us til now for comparable derivatives of biphenyl the angle of torsion was found larger in the gaseous state than in the crystalline state.