Molecular Structures of Ethylene, Allene and Ethylene Oxide and Bridged π-Bond

Abstract

Valence considerations suggest the plane symmetrical form (point group D_2h) for an ethylene molecule. The observed spectra show that there are no bands that occur in the Raman as well as the infrared spectrum of an ethylene gas, proving that the molecule has D_2h symmetry where the molecule has a center of symmetry. From valence theory one would expect for an allene molecule that the C = C = C chain is linear but that the two CH₂ groups lie in planes at right angles to each other and passing through the C = C = C axis, that is, that the molecule belongs to point groups D_2d. The obtained Raman and infrared data of an allene can be interpreted according to D_2d symmetry.

An ethylene oxide can be expected to be a C_2v structure which has the three heavier atoms forming an isosceles triangle .

However the obtained Raman and infrared spectra of an ethylene oxide indicate the lack of coincidence between Raman and infrared frequencies. Therefore an ethylene oxide molecule should have the linear skelton C C (point group D_2h), where the each unpaired p-electron of two C atoms are crosslinked over the central 0 atom by π bonding.

Key Words:

• Molecular Structure
• CH₂=CH₂
• CH₂CH₂
• Bridged
• π-Bond