Summary2-Cyclopentenyl and 3-phenyl-2-cyclopentenyl methyl ketones (15-18, 30, 31) undergo a 1,3-acetyl shift on direct irradiation, and the oxa-di-7c-methane rearrangement to photochemically non-interconverting endo and exo bicyclo-[2.l.O]pentyl methyl ketones on triplet sensitization. Exceptions include the 2-methyl-3-phenyl-2-cyclopentenyl methyl ketone 32 and the I-phenyl-2-cyclopentenyl methyl ketone 44 which are unreactive on direct irradiation and on triplet sensitization, respectively, and the 2-phenyl-2-cyclopentenyl methyl ketones 42 and 43 which do not react under either condition. The reactive triplet of the 3-phenyl-2-cyclopentenyl methyl ketone 30 has been identified as the localized styrene 7c, 7c*-state of ET= 59 kcaVmol by comparison of its phosphorescence at 77 K in rigid glasses with that of l-phenyl-cyclopentene, and by the independence of the quantum yield on sensitizer energy in the range of 61-74 kcaVmol.

MATERIALS & METHODSThe formation and/or increase of ethyl carbamate during storage of wine was monitored at 43°C 32°C and 22°C in the dark, at 22°C under fluorescent light and in a greenhouse with naturally fluctuating temperature and light conditions simulating commercial display of wines. The ethyl carbamate concentration of fifteen selected red and white table and dessert wines was determined initially, and after 3, 6, and 12 months storage. In most wines ethyl carbamate increased as a function of time and temperature. After 12 months in the dark at 43°C. the ethyl carbamate in two red wines increased 20 to 30 times. SamplesBottles of 15 commercial eastern red and white table and dessert wines in either clear or green bottles were obtained from different wine companies. All but two (native K rotundi[oo[in) of the wines were blends of two to five red or white grape varieties of American cultivars, Hybrids and K vinifera types. During the wine making at the wineries, urea was added to dessert wines I and 2 and the alcohol concentration was increased in three of the dessert wines and one white variety (Table 1). The red wine 5 was pasteurized using a short flash to 80°C followed by immediate cooling. The storage study was initiated shortly after bottling. Samples of each of the 15 wines were analyzed for EC and tested for potential EC formation by heating at 70°C for 48 hr in a controlled water bath prior to storage; the EC content measured after this heat treatment is hereafter referred to as "potential EC formation."It increased ihree to nine-fold in nine of the wines, but remained unchanged in four. Light did not significantly influence ethyl carbamate formation, whether in clear or green bottles.

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Dedicated to Professor V . Prelog on his 70th anniversary (16. 111. 76)Sunznzury. 1-Phenyl-3-acet.ylcyclopentene1) (3) undergoes triplet-sensitized oxa-di-n-methane rearrangement to a cu. 3 : 1 mixture of e d o -and exo-l-phenyl-5-acctylbicycio~.l.0;pentane2) (4). The reactive triplet of 3 has been identified as the localized styrene n.,n*-state of ET = 59 kcal/rnol by comparison of its phosphorescence at 77K in a rigid glass with that of I-phenyicyclopentene, and by sensitization quantum yields at room temperature in liquid solution. These quantum yields are independent of sensitizer energy in the range of 61-74 kcal/mol and reach zero for product formation with a sensitizer of Er = 59 kcal/mol. Although S1-t TI intersystem crossing is appreciable under phosphorescence conditions (fDD = 0.05), direct irradiation of 3 at 20" does not lead to triplet rearrangement, and the typical singlet 1,3-acetyl shift to 3-acctyl-3-phcnylcyclopentenes) (8) is observed only.