Abd El-Aal M. Gaber

Photocatalytic oxidation of selected aryl alcohols in acetonitrile

Abstract Photocatalytic oxidation of selected aryl alcohols ( 1 – 7 ) has been carried out by using anatase titanium dioxide catalyst. The main oxidation products were the corresponding aldehydes or ketones and acids, in addition to unidentified minor compounds. Kinetic studies revealed a second-order reaction rate for benzyl alcohol, as a model alcohol, photocatalytic oxidation. The suggested mechanism envisages electron–hole pair formation on the catalyst surface followed by oxidation–reduction reactions.

TiO2-photocatalytic oxidation of selected heterocyclic sulfur compounds

Polynuclear-heterocyclic sulfides (I–IV) were oxidized dominantly to the corresponding sulfoxides and sulfones via TiO2-mediated photocatalytic oxidation in aerated acetonitrile. Also, methylene group in IV and V and active methene groups in VI have been readily oxidized to carbonyl one in a high yield under the same prevailing conditions. A plausible electron transfer mechanism, in which an electronhole pair is generated on the surface of TiO2 by illumination, is suggested for the semiconductor-mediated photocatalysis.

Differential scanning calorimetric study of Bi10Se80In10 chalcogenide glass

Results of differential scanning calorimetry under isothermal and non-isothermal conditions on Bi10Se80In10 glass are reported and discussed. By using the Johnson-Mehl-Avrami equation the activation energies for crystal growth have been evaluated and the crystallization mechanism has been studied. The results indicate that the crystallization process is a two-dimensional growth. The average calculated value of activation energy is 330.2 kJ mol−1for Bi10Se80In10 chalcogenide.

Synthesis of some thiazolo[3,2-a]pyrimidines

Abstract 2-Acetyl-6-cyano-7-ethyl-3-methylthiazolo[3.2-a]-pyrimidine-S-one (3) prepared by reaction of compound (1) with 3-chloropentan-2.4-dione followed by ring closure, was used as starting material to synthesise other heterocyclic compounds. The acetyl compound (3) was easily condensed with different amines to produce the imines (4–8). or the corresponding chalcone (9) when allowed to react with an aromatic aldehyde in presence of zinc chloride. Coupling of compound (3) with benzene diazonium chloride gave the phenylazo derivative (10). When compound (4) was treated with a-haloketones or a-haloesters, the thiazoline or thiazolidine compounds (11–15) were produced. Compound (15) was condensed with aromatic aldehydes to give the corresponding arylidene-derivatives (16a–c). Finally the chalcone (9) was reacted with hydrazine hydrate, phenyl hydrazine and hydroxyl amine to give pyrazolo and isoxazole compounds (17–19) respectively.

Investigation of the decomposition behaviour in supersaturated Al-Zn alloys

The decomposition behaviour in supersaturated Al + (1–6.4) at % Zn has been investigated using electrical resistivity and microhardness measurements in the temperature range from room temperature to ∼500° C. The experimental results showed that (i) both the temperature coefficient of resistivity and the relaxation time of the free electrons diminish as the concentration of Zn increases in the alloy; (ii) the early stage decomposition of the supersaturated alloys via Guinier-Preston zone formation is accompanied by an appreciable increase in the microhardness of about 80 MPa per 1 at % Zn; (iii) the obtained activation energy of 0.41 eV for the precipitation process of the dissolved zinc atoms is close to the migration energy of zinc in aluminium which indicates that the precipitation mechanism is characterized by the migration and coalescence of zinc atoms.

Novel Synthesis of Thieno[2,3-c]Pyridazine and Pyrimido[4',5':4,5]thieno[2,3-c]pyridazine Derivatives

Abstract Novel series of thieno[2,3-c]pyridazines and pyrimido[4′,5′:4,5] thieno-[2,3-c]pyridazines have been synthesized from the readily accessible 4-cyano-5,6-dimethylpyridazin-3(2H)-thione 3b.

SYNTHESIS AND REACTIONS OF SOME NEW 5-CARBONYL(4-AMINO-3-CYANO-2-SUBSTITUTED THIOPHENE-5-YL)-8-HYDROXYQUINOLINE (PART II). SYNTHESIS OF THIAZOLE; ISOXAZOLE; PYRAZOLE, PYRIMIDINE AND PYRIDAZINE DERIVATIVES AS POSSIBLE ANTIMICROBIAL AGENTS

Abstract 5-Carbonyl-(3,4-diamino-2-ethylcarboxylatethieno[2,3-b]thiophene-5yl)-8-hydroxyquino-line (1) reacts with various reagents to afford thiazole, oxadiazole, pyrazole, isoxazole, pyrimidine and pyridazine derivatives (2–13d). The structure of the compounds has been established by elemental analysis. IR, NMR and mass spectra. The compounds thus synthesized were screened for their antimicrobial activity.

THERMOLYSIS AND PHOTOLYSIS OF SOME THIOUREA DERIVATIVES (PART I)

Abstract Thermolysis of N-benzoyl-N′-phenylthiourea (BPTU) on heating in air at 230°C gives NH3, H2S, benzaldehyde, benzil, aniline, azobenzene, benzamide, benzanilide, phenylisothiocyanate, phenyl-cyanamide, thiocarbanilide and benzoylisothiocyanate, whereas thermolysis of N-benzoy1-N′-benzylthiourea (BBTU) affords NH3, H2S, benzaldehyde, benzil, toluene, bibenzyl, stilbene, benzamide, cyanamide, benzylisothiocyanate, benzoylthiourea and benzoylisothiocyanate. Thermolysis of N-benzoyl-N′-α-naphthylthiourea (BNTU) under the same conditions gives NH3, H2S. benzaldehyde, benzil, benzamide, α-naphthylisothiocyanate, α-naphthanilide, α-naphthylcyanamide. benzoylisothiocyanate, α-naphthylamine and N,N′-di-α,α′-naphthylthiourea. Analogous results were also obtained on photolysis of (BFTU), (BBTU) and (BNTU) with the exception of NH3, and the photodegradation products of phenylthiourea, benzylthiourea and a-naphthylthiourea respectively. The main feature of these pyrolyses is the homolysis of the amide and thioa...

SYNTHESIS AND REACTIONS OF SOME NEW 5-CARBONYL(4-AMINO-3-CYANO-2-SUBSTITUTED THIOPHENE-5-YL)-8-HYDROXY QUINOLINE AS POSSIBLE ANTIMICROBIAL AGENTS (PART I)

Abstract S-Alkylation of 5-carbonyl-(4-amino-3-cyanothiophene-2-thio-5-yl)-8-hydroxyquinoline (4) with several halogen- containing compounds afforded the alkylthio derivatives (5a-f). Treatment of 4 with chloramine gave isothiazolothiophene (7), which was allowed to react with diethylmalonate and/or ethylacetoacetate to give the corresponding pyrimidinoisothiazolothiophenes (8) and (9). Ring closure of 5d-f with ethanolic sodium ethoxide gave thieno[2,3-b]thiophene derivatives (6a-c). Acetic anhydride, ammonium acetate, phenylisothiocyanate, nitrous acid, acetylacetone, phosphorus oxychloride, phosphorus pentachloride, hydrazine hydrate and benzoyl chloride gave further cyclization to construct an additional ring. The structure of the compounds has been established by elemental analysis, IR, NMR and mass spectra. The compounds thus synthesized were screened for their antimicrobial activity.

RECENT TRENDS IN THE CHEMISTRY OF THIENOPYRIDAZINES

This review describes the synthesis of thieno[2,3-c]pyridazine, thieno [3,2-c]pyridazine, thieno[2,3-d]pyridazine and thieno[3,4-d]pyridazine derivatives and their reactions.