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A hydrodistilled oil from Corymbia citriodora Hook. produced from leaves harvested in the Réunion Island was analyzed by GC and GC/MS on nonpolar and polar columns, respectively. Nearly 100 constituents were identified. The major constituents were citronellal (63.6%), α-citronellol (7.3%), sopulegol isomers (6.5%), citronellyl acetate (2.6%), p-cymene (2.5%), citronellal dimmers (2.5%), alpha;-pinene (2.1%) and β-caryophyllene (1.2%). Several esters of isobutyric acid (4), monoterpene- (18), and sesquiterpene (15) hydrocarbons, oxides (6), monoterpene alcohols (10), esters (8) and aldehydes (4), (Z)-jasmone, citronellyl citronellate, citronellic acid, eugenol, and some aliphatic and alicyclic derivatives, were presented in trace amounts. On the polar column, further constituents were identified, including menthone, isomenthone, 4-vinylguiacol, and two heavy aliphatic acids: myristic and palmitic acids. [ABSTRACT FROM AUTHOR]

The electronic absorption and fluorescence spectra of coumarin and 11 substituted coumarins were measured in several solvents (dioxane, ethyl ether, ethyl acetate, ethanol, dimethylformamide, acetonitrile, and dimethyl sulfoxide). Ground-state dipole moments were determined in dioxane at 298 K. The results were used to obtain the first excited singlet-state dipole moments of the coumarins under study by the solvatochromic shift method (Bakhshiev, Kawski-Chamma-Viallet, McRae, and Suppan correlations). Also, the ground- and the first excited singlet-state dipole moments were calculated using a combination of the PPP method (π-contribution) and the vector sum of the σ-bond and group moments (σ-contribution). In general, the first excited singlet-state dipole moments of the coumarins are noticeably higher than the corresponding ground-state values, indicating a substantial redistribution of theπ-electron densities resulting in a more polar excited state. There is a reasonably good agreement between the calculated and the experimental dipole moments.