Benign methodology and improved synthesis of 5-(2-chloroquinolin-3-yl)-3-phenyl-4,5-dihydroisoxazoline using acetic acid aqueous solution under ultrasound irradiation.

In the present paper, we have executed the synthesis of substituted 5-(2-chloroquinolin-3-yl)-3-phenyl-4,5-dihydroisoxazolines via the reactions of substituted 3-(2-chloroquinolin-3-yl)-1-phenylprop-2-en-1-ones with hydroxylamine hydrochloride and sodium acetate in aqueous acetic acid solution in 72-90% yields at room temperature under ultrasound irradiation. This method provides several advantages such as operational simplicity, higher yield, safety and environment friendly protocol. The resulting substituted isoxazolines were characterized on the basis of (1)H NMR, (13)C NMR, IR, elemental analysis, and mass spectral data.

Intermolecular proton-transfer in acetic acid clusters induced by vacuum-ultraviolet photoionization.

Infrared (IR) spectroscopy based on vacuum-ultraviolet one-photon ionization detection was carried out to investigate geometric structures of neutral and cationic clusters of acetic acid: (CH(3)COOH)(2), CH(3)COOH-CH(3)OH, and CH(3)COOH-H(2)O. All the neutral clusters have cyclic-type intermolecular structures, in which acetic acid and solvent molecules act as both hydrogen donors and acceptors, and two hydrogen-bonds are formed. On the other hand, (CH(3)COOH)(2) (+) and (CH(3)COOH-CH(3)OH)(+) form proton-transferred structures, where the acetic acid moiety donates the proton to the counter molecule. (CH(3)COOH-H(2)O)(+) has a non-proton-transferred structure, where CH(3)COOH(+) and H(2)O are hydrogen-bonded. The origin of these structural differences among the cluster cations is discussed with the relative sizes of the proton affinities of the cluster components and the potential energy curves along the proton-transfer coordinate.

Identification of free radicals induced by UV irradiation in collagen water solutions.

Electron paramagnetic resonance (EPR) method has shown that hydrogen atoms and acetic acid free radicals appear in surrounding acetic acid-water solution of collagen under ultraviolet (UV) irradiation. These free radicals interact with the collagen molecule; consequently, seven superfine components of EPR spectrum with the split of aH = 11.3G and g-factor 2.001 appear. It is assumed that this spectrum is related to the free radical occurred on the proline residue in collagen molecule. In order to discover .OH hydroxyl radicals even in minor concentration, spin trap 5.5-dimethyl-1-pyrroline N-oxide (DMPO) has been applied. During the irradiation of collagen water solution in the presence of spin trap, EPR spectrum of the DMPO/.OH adduct has not been identified, while the above mentioned spectrum has been observed once the hydrogen peroxide H2O2 and FeSO4 were added to the sample. That means that water photolysis does not take place in collagen water-solution due to UV irradiation. It was suggested that occurrence of hydrogen radical is connected with the electron transmission to the hydrogen ion. The possible source of free electrons can be aromatic residues, photo ionization of which takes place in collagen molecule due to UV irradiation.

Sonolytic degradation of acetic acid in aqueous solutions.

In this work, ultrasonic degradation of acetic acid, which is one of the most resistant carboxylic acids to oxidize, was investigated. The effects of parameters such as ultrasonic power, initial concentration, addition of NaCl or several oxides were studied on the degradation of acetic acid. Acetic acid was sonicated indirectly using an ultrasonic bath with 40 kHz. It was observed that degradation degree increased with decreasing power and initial concentration and with increasing NaCl concentration. Initial degradation degree was enhanced with addition of zeolite and SiO(2).

Light-induced vitamin deficiency in Drosophila melanogaster.

Illumination by visible light (400 Ix) of cultures containing larvae of Drosophila melanogaster can reduce survival (Bruins et al., Insect Biochemistry 21:535-539, 1991). Here we show that the effect of light depends on the presence of propionic or acetic acid in the food medium. We also show that survival is far more affected by illumination of the yeast food media than by direct illumination of the eggs and developing larvae. It is shown that addition of antioxidants to the food prevents light induced mortality. The action of antioxidants suggests that free radicals are important in light induced mortality. We also showed that both yeast and riboflavin (vitamin B2) solutions illuminated with visible light (400 Ix) generate hydrogen peroxide. Other vitamin and amino acid solutions do not produce peroxide in measurable amounts. However, the concentration of photogenerated hydrogen peroxide is far too low to explain the death of eggs and developing larvae upon exposure to light. A 400 Ix light treatment destroys the capability of yeast food media to support survival of larvae. Addition of vitamin C, carotene, tryptophan, nipagin, uric acid, or sucrose to the light treated medium does not restore viability. It is restored when riboflavin is added to the photo-inactivated yeast. A high concentration of pyridoxine also produced an improvement in survival. When riboflavin is treated with light, it cannot support survival on synthetic food media nor can it restore survival on light treated yeast food media. These results show that riboflavin (or a derivative) is a major light sensitive compound of yeast, which can be degraded by light. Light induced loss of riboflavin leads to mortality, because this is an essential dietary vitamin. The vitamin degradation can be prevented by dietary antioxidants. A chromatographic analysis confirms this conclusion.

Role of trace metal ions in chemical evolution. The case of free-radical reactions.

We have studied the effect of iron in the free-radical oligomerization of hydrogen cyanide and acetic acid, and found that iron(II) and iron(III) readily reduces or oxidizes free radicals, respectively. The transient species produced by these reactions do not induce a chain oligomerization process and, therefore, they protect the solute molecules from degradation. Analysis of the available kinetic data for the reactions of a variety of transition metal ions with free radicals indicate that transition metal ions behave similarly to iron. Since Fe, Zn and Mo are essential to all living organisms, and there seems to be no apparent difference in chemical reactivity among transition metal ions towards free radicals, we suggest that these metal ions probably protected the biomolecules from degradation induced by free-radical reactions in the later stages of chemical evolution.