lobna.nassr

Lobna Abdel-Mohsen Ebaid Nassr

Professor - Head Of Chemistry Department- Director of Quality Management Unit - Faculty of Science - Sohag University

Faculty of science

Address: Chemistry Department - Faculty of Science - Sohag University

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Spectrophotometric study of some Mn(II) ternary complexes and their analytical applications
New ternary complexes of Mn(II) with py, bipy, and terpy as primary ligand (L1) and 20,40,50,70-tetraiodofluorescein (I4FlCOOH) as secondary ligand (L2) were prepared. The stoichiometry for these complexes was found to be Mn(II):L1:L2 = 1:2:1, and the complex formula proposed is [Mn(L1)2(I4FlCOO)]?. The effect of substituent groups of L2 and the nitrogen atoms of L1 on complex formation with Mn(II) ... Read more

2009 | Keywords Pectin,
Further mechanistic orientation for the oxidation reaction between alkaline permanganate and poly galacturonic acid methyl ester.
The kinetics of formation of the green manganate(VI) intermediate complex formed during the oxidation of pectin polysaccharide (poly galacturonate methyl ester) (PGME) by MnO4 in alkaline solution at pHP12 have been studied. The rate law was suggested to be: rate = kobs:½MnO4 . The reaction was found to be base – catalyzed and fractional second – order in [PGME]. The ... Read more

Novel mechanistic aspects on the reaction between low spin Fe(II) Schiff base amino acid complexes and hydrogen peroxide
The kinetics and mechanism of the reaction of hydrogen peroxide with some Fe(II) Schiff base complexes were investigated spectrophotometrically in aqueous solution at pH 8 and 35 ◦C under pseudo-first-order conditions. The used ligands were derived from salicylaldehyde or o-hydroxynaphthaldehyde and some amino acids (l-leucine, l-iso-leucine, l-serine, l-methionine and dl-tryptophan). It was found that the formation of the purple interaperoxo ... Read more

2007 | Keywords base hdrolysis, coumarin ,
Reactivity trends of the base hydrolysis of coumarin and thiocoumarin in binary aqueous–methanol mixtures at different temperatures
Rate constants for base hydrolysis of both coumarin and thiocoumarin have been studied in different binary aqueous–methanol mixtures at temperature range from 288 to 313 K. The activation parameters of the reactions were evaluated. Moreover, the change in the activation barrier of the investigated compounds from water to water–methanol mixtures were estimated from the kinetic data. Read more

Synthesis and characterization of some new cobalt(II) and nickel(II) ternary complexes of N-acetyl, N-benzoyl and N-tosyl derivatives of amino acids
A series of some new cobalt(II) and nickel(II) ternary complexes of N-(acetyl)phenylalaninate (acphe), N-(acetyl) tyrosinate (actyr), N-(benzoyl)leucinate (bzleu), N-(benzoyl)phenylalaninate (bzphe), N-(tosyl)glutamic acid (tsglu), N-(tosyl)arginine (tsarg) with certain N-heterocyclic ligands such as imidazole (imi), methylimidazole (mimi), 2,2¢-bipyridyl (bipy) 1,10-phenanthroline (phen) have been synthesized and characterized by elemental analyses, IR and electronic spectra. as well as thermogravimetry. The structure of the cobalt(II) ... Read more

2003 | Keywords Fe(II) complexes, salt effects,
Salt Effects on the reactivity of the base-catalysed hydrolysis of some novel low-spin hydrophobic Fe(II)-amino acid azomethine chelates
Salt effects on the reactivity of base hydrolysis of Fe(II) chelates [naphthylideneisoleucinate (nili), naphthylideneleucinate (nli), naphthylideneserinate (nsi), salicylideneisoleucinate (sili), salicylideneleucinate (sli), salicylidenemethioninate (smi), and salicylidenetryptophanate (sti)] have been investigated in aqueous media containing alkali metal halides and tetra-n-butylammonium bromide (TBAB). NaCl and NaBr exhibited different reactivity trends from those of KBr and TBAB. The observed patterns vary markedly with complex ... Read more

Hydrophobicity and reactivity of base hydrolysis of some novel low spin Fe(II) amino acid Schiff base complexes in some binary aqueous solvent mixtures
Rate constants for base hydrolysis of bis(naphthylidene isoleucinate)iron (II) (nili), bis(naphthylidene leucinate)iron(II) (nli), bis(naphthylidene serinate)iron(II) (nsi), bis (salicylidene isoleucinate)iron(II) (sili), (salicylidene leucinate)iron(II) (sli), bis(salicylidene methioninate)iron(II) (smi), and (salicylidene tryptophanate)iron(II) (sti) have been reported in different binary aqueous mixtures at 298 K. The observed reactivity trends are discussed in terms of the hydrophilic and hydrophobic forms of the complexes investigated, as ... Read more

2003 | Keywords amino acid, Schiff base,
Synthesis and characterization of some novel amino acid Schiff base Fe(II) complexes
New Fe(II) complexes of N-salicylidene- and N-naphthylideneamino acids (H2L) were prepared and characterized by elemental, electronic and IR spectral analyses, conductance and magnetic moment measurements and spectrophotometric determination of the stoichiometry. The stability and solubility of the prepared complexes were determined. The investigated Schiff bases exhibited monodentate divalent tridentate coordination and formed chelates of octahedral structures of the general formulae ... Read more

2002 | Keywords Schiff base, base hydrolysis,
Kinetics of base hydrolysis of novel low spin Fe(II) amino acid Schiff base chelates – Hydrophobic structural effects
The reactivity against OH− ion of some novel Fe(II) complexes of Schiff base ligands derived from salicylaldehyde or _o_‐hydroxynaphth‐aldehyde and some variety of amino acids has been examined in aqueous and aqua‐ethanol mixtures. The rate law and relevant mechanism were assumed. Base hydrolysis kinetics measurements revealed pseudo‐first‐order doubly stage rates because of the presence of mer‐ and fac‐isomers. The evaluated ... Read more