Reinvestigation of the molecular structure of gaseous <i>p</i>-benzoquinone by electron diffraction

Abstract

The molecular structure of gaseous p-benzoquinone has been studied by electron diffraction at a nozzle-tip temperature of 110–125°C. The molecule has D2h symmetry to within experimental error. The results for the more important distance (ra), bond angle, and rms amplitude (l) parameters are rC–H=1.089 Å (0.011), rC=O=1.225 Å (0.002), rC=C=1.344 Å (0.003), rC–C=1.481 Å (0.002), ∠C2C1C6=118.1° (0.3), ∠C3C2H=121.4° (assumed), lC–H=0.077 Å (assumed), lC=O=0.0424 Å (0.0020), lC=C=0.0446 Å (0.0024), and lC–C=0.0546 Å (0.0024). These values are in good agreement with those found in an early electron-diffraction study by Swingle, and except for the length of the carbon-carbon double bond, in excellent agreement with those found in the crystal by Trotter.