4380 authentic 6 on four different columns (10% SE-30. 15% XF-1150, of water and extracted with three portions of ether. The combined 15 % FFAP, and 15 % Carbowax 20M). The nmr spectrum of an ether solutions were dried, and the solvent was removed to leave a impure sample of diketone showed all the bands corresponding to yellow oil. Both the infrared and nmr spectra of this material were the authentic material (as well as some impurity absorptions). similar to, but not identical with, those of8,and fully in accord with er~do,erido-2,6-Dicarboxy-cis-bicyclo[3.3.O]octane(7). The outexpectation for a mixture of 9 and 10. put of a Welsbach Model T-408 Ozonator was bubbled through an cis-Bicyclo[3.3.0]octane-endo,e~~~~~~-2,6-dicarboxylic Acid Anhyice-cold solution of 0.78 g of V in 50 ml of 90 acetic acid until the dride (11). To a stirred solution of 0.20 g of 7 in 150 ml of dry acetonitrile at room temperature was added a solution of 0.19 g exhaust gases turned a 2 % potassium iodide solution dark bronn. After addition of 4.5 ml of 40% peracetic acid in acetic acid to the of distilled dicyclohexylcarbodiimide i n 25 nil of d r i acetonitrile ice-cold, stirred solution, the mixture was heated to reflux for 2 hr. and two drops of pyridine. The solution was stirred for 26 hr The acetic acid was removed to give a quantitative yield of a moist, at room temperature during hliich time a white solid piecipitated. white solid which was recrystallized from water to yield 0.36 g The solid was removed by suction filtration, and the solvent was (38%) of 7 as a white: crystalline solid, mp 222-225"; infrared evaporated from the filtrate to give cu. 100 mg of a colorless oil: infrared: 5.58 and 5.72 p 3 and 5.88 p (diacid). Molecular dis(Nujol): 3-4 and 5.9 p. A second recrystallization from water gave an analytical sample, mp 222--223". tillation gave crude 11 as a colorless liquid (-50 nig): infrared: A m / . Calcd for C10H1401: C, 60.59; H, 7.12. Found: C, 5.58 and 5.72 1.1 (second band stronger), 60.48; H, 7.18. This oil was dissolved in methanol and left at room temperature Equilibration of e~~do,erido-2,6-Dicarbomethoxy-cis-bicyclo[3.3.0]- for 3 days. The methanol \bas removed and the residue was esterified with diazomethane to give a white semisolid which iielded a octane (8). The diacid 7 (0.36 g) was esterified with diazomethane in the usual manner to give 0.43 g of 8 as a yellow oil. Molecular colorless oil upon molecular distillation. Glpc examination indidistillation gave a colorless oil; infrared: 5.77 1.1; nmr (CDCI,): cated that the major component ( 4 3 0 % ) ofthis material was idena sharp six-proton singlet at 6 3.64 (OCH,), a broad four-proton tical with 8 ; infrared comparison confirmed this conclusion. multiplet at 2.8 (CHI: and a broad eight-proton multiplet at 1.7 (CH2). Glpc analysis showed 907; of the major component 8 Acknowledgments. This work was supported by the plus three minor components. Public Health Service in the form of a research grant A solution of 50 mg of this diester in 5 nil of methanol containing (GM 12860) and by the National Science Foundation a catalytic amount of sodium niethoxide was heated to reflux for which provided a n equipment grant (GP 5234) for the 28 hr. Glpc assay showed that one minor component was gone. the major component (8) was reduced to about 5% of the total purchase of the mass spectrometer used in this work. sample, and the two other minor components were increased to The gift of a sample of cyclododecatrienes from the about 95% of the total product in roughly equivalent amounts. Columbian Carbon Company is acknowledged with No further change in the product coniposition was effected by an pleasure. additional 24 hr of heating. The solution was diluted with 40 ml
Emission Spectra and Excited-State Geometry of a-Diketones Ted R . Evans and Peter A. Leermakers Contribution from the Departmerit of Chemistrj., Weslejwn Uiiiceryitj., Middletolisri, Corrnecticut 06457. Receiced March 29, 1967
Abstract: Absorption and emission spectra of a series of open-chain and cyclic aliphatic and aromatic a-diketones have been measured. From absorption, fluorescence, and phosphorescence data singlet- triplet splittings have been measured, and scrutiny of absorption and fluorescence curves permits an estimation of conformational differences between ground and emitting excited states.
T
he geometry of ground states of complex molecules can be qualitatively determined by numerous methods, but few ways exist for determining conforniations or geometries of excited states of the same molecules. Often the configuration is assumed to be the same as that for the ground state. or is assumed to be different on the basis of intuition.' or is deduced by reasonably elaborate measurements. Several groups of workers have clearly shown that the n-r* absorption of a-diketones is strongly dependent upon the intercarbonyl dihedral angle of the dik e t ~ n e . ~ - - Leonard g and ro-workers. in the most ex-
tensive study, found that the long wavelength n - r * transition occurred at 420--500 mp for either cisoid or transoid coplanar dicarbonyl systems, and shifted to substantially higher energies (X,,
