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Imidazolin-2-ones (1) when subjected to dye sensitized photooxygenation in the presence of various solvents like chloroform, benzene, methanol, water either done or in mixture of any two as well as at different pH's (4.4, 7.0 and 9.2) yielded diacylureas as the major reaction products. The reaction was carried out in the presence of cationic (hexadecyltrimethyl ammonium bromide, CTAB); anionic (sodium dodecyl sulphate, SDS) and neutral (ethoxylated nonylphenol, ES) surfactants in aqueous methanol to explore the nature of intermediates. It was obseeved that CTAB enhances the yield of the product while SDS and ES exhibit no effect. The yield of the product was found to be maximum at 2 í— 10-3 M concentration of CTAB. A plausible mechanism of photooxygenation of imidazolin-2-ones involving zwitterionic perepoxides as a prelude to dioxetane formation has been suggested on the basis of observed surfactant, salt and solvent effects.

Imidazolin-2-ones (1) when subjected to dye sensitized photooxygenation in the presence of various solvents like chloroform, benzene, methanol, water either done or in mixture of any two as well as at different pH's (4.4, 7.0 and 9.2) yielded diacylureas as the major reaction products. The reaction was carried out in the presence of cationic (hexadecyltrimethyl ammonium bromide, CTAB); anionic (sodium dodecyl sulphate, SDS) and neutral (ethoxylated nonylphenol, ES) surfactants in aqueous methanol to explore the nature of intermediates. It was obseeved that CTAB enhances the yield of the product while SDS and ES exhibit no effect. The yield of the product was found to be maximum at 2 í— 10-3 M concentration of CTAB. A plausible mechanism of photooxygenation of imidazolin-2-ones involving zwitterionic perepoxides as a prelude to dioxetane formation has been suggested on the basis of observed surfactant, salt and solvent effects.

It is well known that the exposition to air and weather markedly enhances derogation of all artifacts. In this report, the contribution of light (particularly sunlight) to marked speed-up of the oxidation and other changes by exposition to atmosphere will be analyzed. Five major mechanisms of the effect of insolation can be identified: 1. First is a trivial one – the heating effect which enhances all chemical processes. 2. Photoexcitation of material from which the item is made, turning it more reactive toward air oxygen (and to other present substances). 3. Sensitization of oxygen by excitation to singlet state in which it is extremely reactive, and can react even with inert materials. 4. Photochemical transformation of volatile organic compounds (VOC), primarily aldehydes and ketones, that can with oxygen yield organic acids and hydroperoxides which definitely harm majority of materials. 5. In contact of oxygen and another material, upon the absorption of light quanta, a charge transfer process can occur, giving yield to pairs of ion-radicals, which further can be transformed in various reactive products., Dobro je poznato da izloženost vazduhu i vremenskim prilikama dovodi do značajnog narušavanja stanja svih rukotvorina. U ovom radu ćemo anaizirati uticaj svetlosti (naročito sunčeve svetlosti) na značajno ubrzanje oksidacije i drugih promena kao posledica izloženosti atmosferskim prilikama. Može se identifikovati pet glavnih mehanizama efekta insolacije:1. Prvi je trivijalni- uticaj zagrevanja koji ubrzava sve hemijske procese 2. Fotoekscitacija materijala od koga je predmet izrađen, što ga čini reaktivnijim prema kiseoniku iz vazduha( i drugim prisutnim supstancama). 3. Senzibilizacija kiseonika putem ekcitacije u stanje singleta u kojem je on ekstremno reaktivan i može reagovati čak i sa inertnim materijalima.4. Fotohemijska transformacija isparljivih organskih jedinjenja(VOC), prvensveno aldehida i ketona, koja sa kiseonikom mogu dati organske kiseline i hidroperokside koji definitivno oštećuju većinu materijala. 5. U dodiru sa kiseonikom i nekim drugim materijalom, nakon apsorpcije kvantuma svetlosti može doći do procesa prenosa naelektrisanja, što dovodi do parova jon-radikala, koji se dalje mogu transformisati u razne reaktivne produkte.

It is well known that the exposition to air and weather markedly enhances derogation of all artifacts. In this report, the contribution of light (particularly sunlight) to marked speed-up of the oxidation and other changes by exposition to atmosphere will be analyzed. Five major mechanisms of the effect of insolation can be identified: 1. First is a trivial one – the heating effect which enhances all chemical processes. 2. Photoexcitation of material from which the item is made, turning it more reactive toward air oxygen (and to other present substances). 3. Sensitization of oxygen by excitation to singlet state in which it is extremely reactive, and can react even with inert materials. 4. Photochemical transformation of volatile organic compounds (VOC), primarily aldehydes and ketones, that can with oxygen yield organic acids and hydroperoxides which definitely harm majority of materials. 5. In contact of oxygen and another material, upon the absorption of light quanta, a charge transfer process can occur, giving yield to pairs of ion-radicals, which further can be transformed in various reactive products., Dobro je poznato da izloženost vazduhu i vremenskim prilikama dovodi do značajnog narušavanja stanja svih rukotvorina. U ovom radu ćemo anaizirati uticaj svetlosti (naročito sunčeve svetlosti) na značajno ubrzanje oksidacije i drugih promena kao posledica izloženosti atmosferskim prilikama. Može se identifikovati pet glavnih mehanizama efekta insolacije:1. Prvi je trivijalni- uticaj zagrevanja koji ubrzava sve hemijske procese 2. Fotoekscitacija materijala od koga je predmet izrađen, što ga čini reaktivnijim prema kiseoniku iz vazduha( i drugim prisutnim supstancama). 3. Senzibilizacija kiseonika putem ekcitacije u stanje singleta u kojem je on ekstremno reaktivan i može reagovati čak i sa inertnim materijalima.4. Fotohemijska transformacija isparljivih organskih jedinjenja(VOC), prvensveno aldehida i ketona, koja sa kiseonikom mogu dati organske kiseline i hidroperokside koji definitivno oštećuju većinu materijala. 5. U dodiru sa kiseonikom i nekim drugim materijalom, nakon apsorpcije kvantuma svetlosti može doći do procesa prenosa naelektrisanja, što dovodi do parova jon-radikala, koji se dalje mogu transformisati u razne reaktivne produkte.

UV irradiation of the steroidal isoxazolidines 2a, 2b, and 2c in various solvents in the presence of molecular oxygen, results in oxidative cleavage of the epoxyimino bridge to give several products; the N-unsubstituted isoxazolidine 2a afforded the nitro products 3, 4, and 5 and the azoxy compounds 6 and 7, while the N-methyl and N-acetyl derivatives 2b and 2c produced only the nitro compounds 3 and 5 as sole identifiable material. An explanation of the observed photooxygenation processes involving exciplex formation followed by proton transfer from isaxazolidine to molecular oxygen is presented. © 1991.

UV irradiation of the steroidal isoxazolidines 2a, 2b, and 2c in various solvents in the presence of molecular oxygen, results in oxidative cleavage of the epoxyimino bridge to give several products; the N-unsubstituted isoxazolidine 2a afforded the nitro products 3, 4, and 5 and the azoxy compounds 6 and 7, while the N-methyl and N-acetyl derivatives 2b and 2c produced only the nitro compounds 3 and 5 as sole identifiable material. An explanation of the observed photooxygenation processes involving exciplex formation followed by proton transfer from isaxazolidine to molecular oxygen is presented. © 1991.

Partial Contents: Chemical Research at the Institut fuer Strahlenchemie, Muelheim; Photooxygenation Research in Strasbourg; Speech Recognition at the UK National Physical Laboratory; EMMA (Elaboratore Multi Mini Associativo)--Italy; Academic Titles and Degrees at Italian Universities--What's in a Title? From Antennas to Acoustic Microscopes at London's University College; Sonar and Signal Processing at Loughborough; Deutsches Kunststoff Institut; Marine Research in Iceland; The Icelandic Hydrographic Office; Fuzzy Sets; Operations Research at Ciba-Geigy and in Some Belgium Universities; UK Solid State Physics Conference; Solid State Physics at Sunderland Polytechnic (UK); and XUV Gain at Hull.