Gamal A Ahmed

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Spectrophotometric detection of the formation of short-lived hypomanganate(V), [KCAR-Mn(V)O43-], and manganate(VI), [KCAR-Mn(VI)O42-], intermediates has been confirmed through the oxidation of K-carrageenan (KCAR) by potassium permanganate in alkaline solutions of pH's >or= 12 using a conventional spectrophotometer. The short-lived transient species were(More)
Spectrophotometric evidence for the formation of hypomanganate(V), [CAR-Mn(V)O43-], and manganate(VI), [CAR-Mn(VI)O42-], intermediate complexes has been confirmed during the oxidation of iota- and lambda-carrageenan-sulfated polysaccharides (CAR) by alkaline permanganate at pHs 12 using a conventional spectrophotometer. These short-lived intermediate(More)
2-Hydroxy- and 2-Mercapto-3,4-dihydro-4-oxo-6-(furyl)-pyrimidine-5-carbonitriles (3a, b) were synthesized by two different routes. Methylation of 3a with methyl iodide gave the S-methyl derivative 4, which could also be prepared by two other different methods. The reaction of 4 with phosphorous oxychloride yielded the 4-chloro-pyrimidine derivative 6, which(More)
The kinetics of oxidation of iota- and lambda-carrageenan as sulfated carbohydrates by permanganate ion in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm(-3) have been investigated spectrophotometrically. The pseudo-first-order plots were found to be of inverted S-shape throughout the entire courses of reactions. The initial rates(More)
Ethyl (2,5-Dimethylphenyl) pyruvate (2) condensed with o-phenylenediamine, ethylenediamine, semicarbazide and thiosemicarbazide and gave quinoxaline derivative (3), dihydropyrazine derivative (9) and 1,2,4-triazine derivatives (10, 11) respectively. Compound (3) reacted with phosphorous pentasulphide, polyphosphoric acid, semicarbazide hydrochloride and(More)
6-Oxo-4(2-thienyl)-2-thioxo-1,3-dihydropyrimidine-5-carbonitrile (1) was synthesized and reacted with alkyl halides to give the S-alkyl compounds (2a,b), which reacted with phosphorous oxychloride to yield (3a,b). Reaction of 3a,b with phenyl-hydrazine, hydrazine hydrate, ammonia, acid hydrazides and thiourea leads to formation of the compounds (4a,b), the(More)
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