Peter Markov

On the photosensitivity of dibenzoylmethane, benzoylacetone and ethyl benzoylacetate in solution

Abstract The influence of sunlight on the keto-enol ratio of dibenzoylmethane, benzoylacetone and ethyl benzoylacetate in heptane solution was examined. It was shown that the tautomeric equilibrium is strongly displaced to the keto form. Important differences in the photosensitivity of β-diketones and β-ketoesters depending on the structural features and the nature of irradiation have been established.

Effect of some 2-arylbenzothiazoles on the photo-degradation of poly(vinyl chloride)

The action of some 2-phenyl-benzothiazoles (BT) as photo-sensitizers of the photo-degradation of poly(vinyl chloride) (PVC) is studied. On irradiation with unfiltered light in air, polyene sequences are formed. The initial dehydrochlorination of PVC as well as the development of polyene sequences strongly depend on the nature of the compounds. Complexes ((BTH)+ Cl−) formed from BT and HCl (liberated from the photo-dehydrochlorination of PVC) are observed. The role of these complexes is discussed and their effect on the physical and mechanical properties of PVC is considered. The data can be explained by the strong acceptor action of the excited states of BT.

Effect of UV irradiation on some β-dicarbonyl compounds in solution

Abstract The pronounced effect of UV-polychromatic irradiation in shifting the position of keto-enol equilibrium has been described and in particular the influence of UV irradiation on the keto-enol ratio of ethylacetoacetate in cyclohexane solutions was examined. It was shown that the equilibrium is strongly displaced to the keto form. The results indicate clearly that the effect of the UV-irradiation on the keto-enol equilibrium is reversible.

Reactions of calcium and magnesium naphtalenides with ethyl esters of 2-bromopropionic and 2-bromobutyric acid in liquid ammonia

Abstract The reaction in liquid ammonia of magnesium naphtalenide with the ethyl esters of 2-bromoproionic and 2-bromobutyric acid gives after hydrolysis the corresponding 2,2′ -dialkylsuccinic acids, whereas calcium naphthalenide reacts to give in the former case 2,2′ -dimethyl anhydride, and 2-hexene-3,4-dicarboxylic acid in the latter. Possible reaction mechanisms are discussed.

Über die Reaktion von Biphenyl mit Magnesium in flüssigem Ammoniak

The interaction between magnesium and biphenyl in liquid ammonia has been studied. It was shown that the metal adduct formed reacts slowly with the reaction medium to give tetrahydroderivatives of biphenyl.A comparative study was carried out in order to reveal the influence of the metal used on the reaction pathway. It was found that the nature of the reaction products markedly differs when lithium, sodium or magnesium were used in the reaction.Possible reaction mechanisms are discussed.

On the photogalvanic properties of alkylpyridinium salts in solution

Abstract The photoelectrochemical behaviour of alkylpyridinium salts which arises in water or in water—methanol solutions was studied. The data obtained show that the photopotential is due to a photogalvanic effect. The maximal values of electrode potential and the energy of the photogalvanic cell depend on the type of the salt and solvent used, as well as on the absence of atmospheric oxygen in the irradiated solution. An important characteristic of the process is its reversibility. After discharging the photogalvanic cell by applying an external load in the circuit, the subsequent irradiation of the organic solute repeatedly leads to the appearance of a photo-induced electrode potential.

Measurements of the Relaxation Kinetics of Photo-Excited Enol Form of Dibenzoylmethane

The decay rate of the excited state of the enol form of dibenzoylmethane (DBM) in different solvents is measured directly using nanosecond light pulses. The observed relaxation kinetics is explained by the formation of three intermediate forms of the excited cis-enol form of DBM. The decay rates of the intermediates and their absorption cross sections for λ = 266 nm are reported too.

Influence of ultraviolet light on some copper chelates of β-dicarbonyl compounds : Spectral evidence for a photoactivated metallotropy

Abstract The influence of ultraviolet light on heptane solutions of the copper chelates of several β-dicarbonyl compounds has been followed by spectroscopy. Reversible transformations are apparent, leading us to assume the presence of a photoactivated metalotropy.

Photopotential and photocurrent induced by an aqueous solution of aliphatic alcohols

This paper deals with the photogalvanic behaviour of aliphatic alcohols in aqueous solution. It is found that UV-illumination causes the appearance of photopotential and photocurrent. The maximal values of the electrode potential and energy of the photogalvanic cell depend on the type of the alcohol used, its concentration, the temperature and the pH of the irradiated solution. An important characteristic of the phenomenon observed is its reversibility. After discharge of a photogalvanic cell by application of an external load in the circuit, a subsequent irradiation repeatedly leads to the appearance of photoinduced electrode potential and photocurrent. A possible mechanism of the photogalvanic effect is discussed.

Photo-induced tautomerism of some benzoylacetanilides in solution and polymer films

Abstract UV spectroscopy methods were used to investigate the photoketonization of some benzolacetanilides in solutions (cyclohexane and ethanol) and polymer films (polymethylmethacrylate—PMMA). The rate constants and quantum yields of the process were determined and important differences in the photosensitivity of β-ketoanilides depending on their structure were established. Quantum-chemical calculations of the ground and excited states of the β-ketoanilides show that the excited triplet state (T 1 ) of benzoylacetanilides is expected to be active in the photochemical reactions. The photo-induced ketonization in polymer films was also investigated. A good photostabilizing effect of these compounds on the polymeric materials can be expected.