Zoltán Dinya

Photocatalytic degradation of thiocarbamate herbicide active ingredients in water

It has been shown that a wide range of organic compounds in aqueous solutions is photocatalytically oxidized to carbon dioxide in the presence of titanium dioxide with near-UV radiation. The photocatalytic mineralization of thiocarbamate derivative pesticides (EPTC, butylate, molinate, vernolate and cycloate) in water by illuminated TiO2 has been studied. The determination of the effects of various kinetic factors on the photocatalytic degradation and the determination of the nature of the principal intermediates form part of the focus of this study. The degradation rate of these thiocarbamates in a continuous recirculation mode approximates first-order kinetics. It was demonstrated that photocatalyzed degradation of thiocarbamate active ingredients does not occur instantaneously to form carbon dioxide, but through the formation of long-lived intermediate species. Photocatalytic intermediates detected during the degradation of thiocarbamates were identified by GC/MS techniques. Intermediates detected in the photocatalytic oxidation of thiocarbamates in water solutions are in excellent agreement with products identified from the atmospherically important reactions of OH radical with thiocarbamates. Particular attention will be paid to the carbon dioxide formed from the illuminated suspension in order to demonstrate not only apparent destruction but also complete mineralization. The degradation of a two-component mixture was carried out and compared to results obtained with single-component studies.

Photodegradation study of some triazine-type herbicides

Abstract Triazines are amongst the most widely used herbicides. Since triazines can be found in many environmental compartments, their fate in ecosystems and the characterization of their degradation pathways in the environment are to be determined. In this paper we report on a study intended to investigate the photodegradation of some triazine-type herbicides: atrazine, cyanazine, terbuthylazine and terbutryn. The rate of photodegradation process was determined, and degradation schemes were outlined for the compounds studied. Moreover, experiments with different degrading energies were carried out in order to gain information about the effect of total degrading energy on the photodegradation process. The most significant processes of photodegradation of triazines are the partial or complete loss of side-chains, or rather the substitution of the heteroatom-containing side-chain to hydroxyl-group. Besides consecutive processes, loss of the different side-chains takes place parallely also, thus, different metabolites will be formed having mixed side-chains, until the cyanuric acid and 2-amino-4,6-dihydroxy-1,3,5- s -triazine are formed by losing all the side-chains. The presence of the dimer products could be detected during the degradation of all triazines. This proves the radical character of processes occurring during the photodegradation. Increasing the degradation energy (15 to 125 W) has raised the degradation rate by 2–5, and the chlorine containing metabolite—which was still present in the completely degraded mixture during the low-energy experiments—has completely disappeared from the mixture, thus, the increased degrading energy is favorable to the formation of less dangerous, nature identical metabolites.

Cycloaddition reactions of carbohydrate derivatives. Part IV. Synthesis of a tetrahydroxyindolizidine through a cyclic nitrone prepared from D-xylose.

Intramolecular conjugate addition of the oxime from aldehyde 5 led to the formation of cyclic nitrone 6. 1,3-Dipolar cycloaddition of the latter with methyl acrylate gave the bicyclic 7 with high diastereoselection. Subsequent four-step transformation of 7 resulted in the tetrahydroxyindolizidine derivative 11.

A straightforward route to hydantocidin analogues with pyranose ring structure

Abstract Partial hydrolysis of the nitrile moiety in acetylated 1-bromo-glycopyranosyl cyanides 1 and 9 mediated by TiCl4 gave C-(1-bromo-1-deoxy-glycopyranosyl)formamides 2 and 10 whose reaction either with AgOCN, AgSCN or KSCN in nitromethane resulted in the formation of glycopyranosylidene-spirohydantoins 3, 11 and 15 and -thiohydantoins 7 and 16. Zemplen-deacetylation gave the pyranoid epi-hydantocidin analogues 4 and 12, and thiohydantocidin analogues 8 and 17, respectively.

Asymmetric induction by amino acid ligands in chromium(II)-assisted reduction of ketones

Abstract Asymmetric reduction of acetophenone by Cr(II)/amino acid/water/DMF system is reported. Chemical yields up to 94%, enantiomeric excesses up to 74% were observed. The relevance to the Nozaki–Hiyama–Kishi reaction is discussed.

Formation of C60 and polycyclic aromatic hydrocarbons upon electric discharges in liquid toluene

Abstract A great number of polycyclic aromatic hydrocarbons and C60 are formed upon the effect of electric discharges in liquid toluene between graphite or pyrographite electrodes applying high voltage AC.

Thermal, decomposition of some new spiro-1-pyrazolines

Abstract The thermal decomposition of spiro-1-pyrazolines 2 obtained by the cycloaddition of exocyclic α,β-unsaturated ketones with diazomethane gives spirocyclopropanes 4 with high selectivity and the new β-methyl-3-benzylidene derivatives 3. The configuration and conformation of the thermolysis products 3 and 4 were elucidated by different n.m.r. methods.

Spin adducts of group IVB organometallic radicals with Thioketones. an esr study

Abstract The radical adducts resulting from the reaction between group IVB organometallic radicals MR 3 (M = Si, Ge, Sn; R = alkyl or aryl) and a number of thioketones of the chromone and flavone series have been investigated by ESR spectroscopy. The spectral parameters obtained for these species have been compared with those of similar adducts of the corresponding ketones. Both classes of radicals adopt an orthogonal conformation, and the differences between the former and the latter paramagnetic species can be accounted for by the different electronegativity of oxygen and sulphur. the effects of substitution of the heterocyclic oxygen with a sulphur or selenium atom on the spin density distribution are likewise explained. INDO calculations have been carried out on the model systems CH 2 XSiH 3 (X = O, S).

A new approach for the synthesis of naturally occurring dihydrobenzo[b]furan-type neolignans of potential biological activity

Abstract A new synthesis of racemic naturally occurring neolignan 1 possessing a PGI 2 inducing effect was achieved via the 2,3-dihydrobenzo[ b ]furan derivative 2 , starting from the commercially available materials o -vanillin and acetovanillone.

Preparation of acylated pyranoid glycals in neutral aqueous medium by using chromium(II) complexes as reagents

Abstract Reactions of 2,3,4,6- tetra -O- acetyl -α- d -glucopyranosyl bromide (3) with chromium(II)L complexes (L = EDTA, NTA, IDA, GLY, MAL) in neutral (5 3,4,6- tri -O- acetyl-1,5-anhydro-2-deoxy- d -arabino- hex-1-enitol (13) in 70–90% yields and >95% purity. Complexes of Cr(II) with L = EDTA, NTA were similarly efficient with 2,3,4,6- tetra -O- acetyl -α- d -glucopyranosyl chloride (2) in furnishing glucal 13, while with L = IDA, GLY, MAL hydrolysis of 2 could not be suppressed. Under the same conditions [CrII(EDTA)]2− also efficiently gave the corresponding glycals 14–19 from 2,3,4,6- tetra -O- benzoyl - ( 4 ) and 2,3,4,6- tetra -O- pivaloyl -α- d -glucopyranosyl bromide (5), per-O-acetylated α- d -galactopyranosyl chloride (6) and bromide (7), α- d -mannopyranosyl chloride (8), α- d -xylopyranosyl chloride (9), and bromide (10), β- d -arabinopyranosyl bromide (11), and α- l -rhamnopyranosyl chloride (12).