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3 International Letters of Chemistry, Physics and Astronomy

3 2013

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Theoretical Inversion of Amino Acids (Alanine and Aspartic Acid) by Semi-empirical Methods

Mohamed M. E.

International Letters of Chemistry, Physics and Astronomy

2013

Vol. 7, iss. 1

37--44

The inversion reaction coordinate of free amino acids (alanine, aspartic acid) have been computationally calculated by semi-empirical methods AM1. A transition state for free alanine and aspartic acid were obtained as a three membered ring in which the α-C-H and α-C-CH3 are slightly elongated, 1.2 and 2.17 Å respectively in the alanine transition state. The activation energy of alanine is 77.52 kcal/mol in the gas phase and 76.66 kcal/mol in aqueous phase, and for aspartic acid is 54.87 kcal/mol in the gas phase and 50.86 kcal/mol in aqueous phase.

Synthesis and Spectroscopic Characterization of l-aspartic Acid Complexes with Metals of the Lanthanides Family

Mohamed M. E.

International Letters of Chemistry, Physics and Astronomy

2013

Vol. 6

91-115

The complexes between l-aspartic acid and metals of lanthanide series (La3+, Pr3+, Eu3+, Gd3+) have been prepared and characterized using a variety of techniques including, infrared spectroscopy, 1H NMR, 13C NMR, elemental analysis and metal contents. The sought metal effect on the electronic environment of the chiral carbon and its neighbouring atoms was observed in case of Europium and Praseodymium. The 13C downfield shift indicates a lower electron density at the carbon with consequent downfield shift observed on the ?-H attached to it increasing its acidity.

Inhibition of Brass Corrosion in Acid Medium Using Thiazoles

Taha K. K., Mohamed M. E., Khalil S. A., Talab S. A.

International Letters of Chemistry, Physics and Astronomy

2013

Vol. 9, iss. 2

87-102

Brass as an alloy composed mainly of copper is great industrial uses such as heat exchangers and similar other facility due to its good thermal properties. Due to the presence of the considerable ratio of zinc the alloy suffers from zinc dissolution or dezincification. Dezincification rate increases with the increase in the ratio of zinc in the alloy. In this study benzothiazole (BTH) and its substituent’s 2-methylbenzothiazole (MeBTH), 2-aminobenzothiazole (ABTH), 2-mercaptobenzothiazole (MBTH) and 2-phenylbenzothiazole (PhBTH) have been used as corrosion inhibitors for α-brass in stirred 0.1 M HClO4. The methods of investigation include weight loss, Tafel and linear polarizations and electrochemical impedance spectroscopy. The order of inhibition efficiency (% E) was calculated and the values obtained has indicated the sequence of inhibition efficiency was found to be BTH < MeBTH < ABTH < PhBTH < MBTH. The calculated values of thermodynamic parameters support this order. The inhibitors were found to suppress the corrosion rate by the formation of films which were identified by IR, SEM and EDAX techniques.