5608hydride (mp 87-89", lit.23 92-93"). The deuterated compound (2) was prepared by reduction of dibenzoylethylene with lithium aluminum deuteride-d4 99% D (Alfa Inorganics, mp 84-85"). Melting points are uncorrected. Infrared spectra were recorded on a Beckman 1R 10 spectrophotometer, ultraviolet spectra on a Cary 15 spectrophotometer in cyclohexane, emission spectra on a PerkinElmer MPF-ZA with phosphorescence attachment in an etherisopentaneeethanol (EPA) glass, and mass spectra on a CEC 21-104 mass spectrometer with an ionization voltage of 15 eV. The structures assigned to 1 and 2 are in agreement with their ir, uv, nmr, and mass spectra.Quantum Yields. Solutions 0.05 M in ketone and about 0.005 M in tetradecane internal standard were degassed and sealed under vacuum in 13 mni 0.d. Pyrex tubes. The tubes were photolyzed on a merry-go-round apparatus at 25 2" using a Hanovia 450-W medium pressure mercury lamp and a potassium chromate filter solution to isolate 31 30-A irradiation. Photolyses were carried to less than 10% except when dependence on extent of conversion was studied. The photolyzed solutions were analyzed for acetophenone formation and loss of starting material on a Hewlett-Packard 5750 dual flame gas chromatograph with a calibrated 5 ft X lis in. column of 4 z Q F 1 and 1 Carbowax 20 M on Chromosorb G . Vpc traces were analyzed with a Gelman planimeter. Benzophenone-benzhydrol actinometersz4 were photolyzed simultaneously and analyzed at 3600 A using a Beckman DU spectrophotometer with Gilford attachment Model 222. Variable-temperature studies employed the same apparatus immersed in a water bath thermostated to =t 1 ' . Reported quantum yields are the result of multiple vpc analyses of one or more solutions, overall accuracy f5Z. Light intensities of approximately 5 X 10-8 Einstein I.-' s a -1 were used in all cases.Quenching Studies. Samples were prepared and analyzed as for quantum yield determination except that varying amounts of transpiperylene (Chemical Samples) were added to the solutions. Five concentrations of piperylene, in addition to blanks containing no piperylene, were used for each Stern-Volmer plot.Intersystem Crossing Quantum Yields. The method of Lamola and HammondZ6 was used. Degassed benzene solutions of 0.05 Macetophenone and 1 and 2 each 1.0 M insis-piperylene (Chemical Samples) were irradiated for 6 hr at 3130 A. Analysis for piperylene isomerization was on a 10 ft X in. column of 25% sulfolane on Chromosorb P a t 40".Mass Spectra Samples. Samples were prepared, degassed, irradiated for varying periods, and analyzed in the same way as for quantum yield determination. The benzene solutions were then washed twice with 10 ml of water and dried with magnesium sulfate, and the benzene was removed. The residue was recrystallized at 0" from chloroform-pentane and the crystalline product analyzed on a CEC 21-104 mass spectrometer with an ionization voltage of 15 eV. The molecular ion region was scanned several times for each sample and the isotopic composition calculated as an ave...

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Die optisch aktiven Thiocarbonate (I) spalten thermolytisch CO2 ab und gehen in die Sulfide (II) über.