X-Ray and Electron Diffraction of Iodine and the Diiodobenzenes

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Abstract
The crystal structures of 1,3 and 1,4 diiodobenzene were determined from the x‐ray diffraction patterns of single crystals. The separations of the iodine atoms in the molecules were found to be 6.85 and 5.92A, respectively. These values are in agreement with results obtained by analysis of the electron diffraction patterns given by the vapors of these compounds. The most satisfactory explanation of the electron diffraction results for 1,2 diiodobenzene requires the I–C valence directions to be bent by about 10° from symmetrical positions in the plane of the benzene ring. In this molecule the I–I distance was found to be 4.00A, which is approximately the same as the minimum intermolecular iodine distances in crystals of the other isomeric diiodobenzenes. Electron diffraction was obtained from vapors of carbon tetrachloride and iodine. The separation of the iodine atoms in the latter molecule was found to be 2.64A; a value in agreement with band spectra data and with previous crystal structure analysis.