Molecular Structure of Ethylene

The structure of gaseous ethylene was investigated by the sector-microphotometer method of electron diffraction. The major internuclear distances, in terms of center of gravity parameters rg(0), were found to be C–H = 1.084±0.003 A, C=C = 1.3327±0.002 A, and C–—H = 2.120±0.006 A, and the angle H–C–H was 115.5±0.6°. Root-mean-square amplitudes of vibration were lC–H = 0.0768±0.003 A, lC=C = 0.0439±0.002 A, and lC–H = 0.102±0.006 A, which values agree reasonably well with values calculated from spectroscopic data. The uncertainties reported represent standard errors computed by a simplified method from least squares analyses of parameters. Discrepancies between the diffraction results and those of new infrared and Raman results are discussed in terms of the arbitrariness arising from the different operational definitions of bond distances and angles involved.