Thiourea, electron diffraction studie

Reports on the crystal structure of selenourea rqrpeared in the early 1960s, which gave preliminary accounts of the unit-cell dimensions of selenourea [5]a,b] and information about the carbon-selenium double bond in the crystal structure of /V-phenyl-AT-benzoylselenourea [57c]. More accurate determination of the lattice parameters and atomic positions of selenourea was carried out at room temperature and at 173 K by Rutherford and Calvo in 1969 [52]. All of these reports assigned the structure to one of the enantiomorphous trigonal space groups P3 and P32 with Z=27, which differs from an earlier electron diffraction study based on space group Pnma with a = 6.48, b = 8.75, and c = 7.04 A and Z=4 [55a] that can be compared with the room-temperature phase of thiourea. The lattice parameters of selenourea firom these studies are listed in Table 6. 

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