抄録
Infrared spectrum of isoöctane-thiourea adduct in KBr disk showed that the adduct was already decomposed. In order to examine the assumption of Stewart that thiourea adduct is probably decomposed by compression, thiourea adducts of 10 compounds were prepared and their infrared absorption spectra were measured in KBr disk, examining absorptions at 13.75 and 13.9 μ for the evidence of decomposition. It was thereby found that thiourea adducts other than those of camphor, 9-oxocamphor, turmerone, and decalin underwent decomposition. When KBr disks of these adducts were prepared without evacuation, the disks powdered, and infrared spectra measured in Nujol, decomposition did not occur in adducts other than those of isoöctane and carbon tetrachloride. Since their behavioir towards decomposition is different according to the kind of guest molecule and the decomposition differs according to whether the adduct is pressed under the atomospheric or diminished pressure, this decomposition is not due to destruction of crystal lattice by compression but the liberation of volatile molecules due to degree of evacuation and generation of heat by compression leaving thiourea in rhombic state. The fact that adducts formed from non-volatile compounds do not undergo change on compression was confirmed by thermal analysis. This was also proved by the fact that 9-oxo-camphor-thiourea adduct formed a stable tablet.
