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    Fluorescence emission and photooxidation studies with 5,6-and 6,7-benzocoumarins and a 5,6-benzochromone under direct and concentrated sun
    (Elsevier Science Sa, 2002) Karapire, C; Kolancilar, H; Oyman, Ü; Icli, S
    4-Methyl-8-hydroxy-benzo(6,7)coumarin, 1,4-methyl-6-hydroxy-benzo(5,6)coumarin, II, and 2-methyl-6-hydroxy-benzo(5,6)chromone, III, have shown similar absorption and fluorescence emission spectra. Fluorescence emission quantum yields for I and III are found to be very low, phi(f) = 0.02, but 4-methyl-6-hydroxy-benzo(5,6)coumarin, II, has a eight-fold higher fluorescence quantum yield of the other two specie, in acetonitrile solution, of = 0.16. Quenching of anthracene fluorescence emission by 1, II and III are found to give k(q) values of 1.0 x 10(7)-1.2 x 10(9) M-1 s(-1). Benzo(5,6)coumarin, II, which gives the most intense fluorescence also presents the highest quenching rate, k(q) = 1.2 x 10(9) M-1 s(-1). Experimentally determined k(q) values are seen to correlate well with the free energy of electron transfer (DeltaG(ET)) which are calculated to be in the range of -8.0 to -9.4 kcal/mol, where benzo(5,6)coumarin, II, gives the lowest free energy of electron transfer DeltaG(ET) = -9.4 kcal/mol. These results indicate that I-III behave as electron acceptor moieties toward a condensed aromatic ring, anthracene. The Stokes shift values of 88-105 mm and broad fluorescence emission bands respect to absorption-excitation bands, indicates a molecular structure change in the excited states of I-III. Fluorescence lifetimes of 0.1-0.9 ns in I-III, singlet oxygen quantum yields of 0.15 and 0.40 for I and II, respectively, may be taken as evidence of singlet-triplet intersystem crossings. The photooxidation products of alpha-terpinene, sensitised by II, under direct and concentrated sun light conditions that are mainly p-cymene and ascaridole. In accordance with literature data on coumarin derivatives, benzocoumarins also seem to produce singlet oxygen and beside singlet oxygen, in addition super oxide anion radical production appear to be dominant especially under concentrated sun light. Under direct sun light conditions ascaridole is the major product. Some by-products of alpha-terpinene photooxidation are also determined at GC-MS analysis. Those by-products are assumed to be generated from ascaridole decomposition. (C) 2002 Elsevier Science B.V All rights reserved.
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    Investigation of the Pechmann reaction between 2,7-dihydroxynaphthalene and ethyl a cetoacetate with different condensing agents.: Synthesis of benzocoumarin and benzochromone systems and their bi- and bis-derivatives
    (Scientific Publ-India, 2003) Kolancilar, H; Oyman, Ü
    Attempts were made to synthesise the benzocoumarin and benzochromone systems by Pechmann reaction. As an extension, it was also planned to make bi- and bis-derivatives of these compounds. 2,7-Dihydroxy naphthalene (DHN) and ethyl acetoacetate (EAA) were chosen as starting materials and 80% H2SO4, PPA and HClO4 were used as condensing agents. H2SO4 gave a benzochromone with a low yield together with isomeric benzocoumarins. PPA gave angular benzocoumarin and benzochromone but no linear benzocoumarin was obtained. When HClO4 was employed the isomeric benzocoumarins were obtained with no indication of the formation of benzochromone ring. Attempts were also made to couple some of the compounds synthesised. Only one bi-benzocoumarin was obtained in one case. No angular benzocoumarin and angular benzochromone compounds gave the coupling reaction. Also, to obtain bis-derivatives, the Mannich reaction was applied.
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    Preparation of laurel oil alkanolamide from laurel oil
    (Wiley, 2004) Kolancilar, H
    A low-temperature synthesis of laurel oil alkanolamides directly from laurel oil and ethanolamine was carried out in essentially quantitative yields. The ethanolamine/laurel oil molar ratio used was 10:1. Even though amine served as a catalyst in the reaction, we used sodium methoxide at a ratio of 0.2-2% as a second catalyst. The reaction was complete in 1-9 h at room temperature. The identity of the amide was confirmed by IR and C-13 NMR spectroscopy.