Abstract
The molecular structure of tetravinylmethane has been investigated by gas-phase electron diffraction. Four CC bonds may be axes of torsion in this molecule, hence a priori, an enormous number of conformers are possible. Preliminary analysis of the experimental radial distribution allowed the reduction of the number of conformations to be considered to four. Subsequent least-squares refinement indicated the presence of one conformational isomer only. This conformation is similar to that obtained by X-ray crystallography. The all-carbon frame of the molecule may be characterized by a carbon tetrahedron standing on three CC legs out of one of the sides (2–3–4) of this tetrahedron, of approximately C 3 symmetry. The fourth CC bond is positioned as if it were a handle of the tetrahedron, approximately eclipsing one of the CC bonds. Some fragments of the carbon skeleton display further approximate local symmetries, such as a twofold axis of the C7C3C1C5C9 chain and a symmetry plane of the C8C4C1C5C9 chain. The following bond lengths ( r g), bond angles, and dihedral angles characterize this structure: CH 1.101 ± 0.002 A ̊ ; CC 1.336 ± 0.003 A ̊ ; CC 1.522 ± 0.003 A ̊ ; CCC 127.0 ± 0.2°; CCH 123.7 ± 0.7°; CCC 109.5° (assumed); CCH 117.0° (assumed); ZC1C2C6 24.8 ± 1.5°; ZC1C3C7 − 121.7 ± 2.7; ZC1C4C8 − 68.6 ± 1.8°; ZC1C5C9 39.8 ± 2.4°, where C1 is the central carbon atom and Z is the bisector of the C2C1C3 angle. A torsional angle is zero in the eclipsed position. Any clockwise torsion, closest to us, out of the eclipsed position is positive.
Published Version
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