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الاثنين، 24 مارس، 2014

Synthesis of Potential Biologically Active Synthones from Cellulose Derivatives

Title:Synthesis of Potential Biologically Active Synthones from Cellulose        Derivatives 
Author        :  Georgina Nabil Samaan
Collection   : M.Sc. Chemistry
Abstract:  
In this thesis the preparation reactions, antibacterial effects of some modified cellulosic compounds were studied. The cellulosic host was used in the dialdehyde form by the oxidation to give Di-Aldehyde Cellulose (OAC). The cellulosic compounds were prepared by reaction of DAC with Ortho- Phenylene Di-Amine (OPDA) and two of its analogs namely 3,4-Di-Methyl Ortho-Phenylene Di-Arnine and 4,5-Di-Chloro Ortho-Phenylene Di-Amine. The reaction is a condensation addition reaction. A study of the reaction mechanism was carried out. It was also validated that the reaction produces a seven membered ring product. The kinetic study of the reaction focused on the variables of pH (1, 1.5,3, and 4), temperature (room temp. and 60-65°C), time (3mins up to 4 days), method of stirring (continuous and occasional), and the method of heating (heat bath or microwave). The study was carried out for all three of the OPOA analogs. The general deductions concern those experiments with bath heating and microwave heating. In bath heating as temperature increases the yield and rate of reaction increase. The pH of the medium had a negative effect on the yield and reaction rate since the reaction proceeds via nucleophilic addition which is faster in W rich conditions. However the prolonged exposure to high temperatures and low pH values causes the degradation of the products thermally and chemically. Continuous stirring caused increase in yield but destroyed the fiber form of the product, thus occasional shaking was used instead to eliminate this problem. In microwave heating the rate of the reaction was substantially higher than with bath heating and yield as high as 50% were reached in only 4 mins. The effect of pH was positive on reaction rate and yield since the severe heating by irradiation also increased the rate of degradation of the products especially at low pH values. Thus prolonged irradiation at high pH increased yield but decreased yield at low pH due to degradation. The biological activity of reaction product was studied on gram positive and gram negative bacteria. The highest biological effect was observed with DAC reacted with 340MOPOA, the second best performance was with DAC reacted with OPOA. Both showed activity with gram +ve and gram - ve bacteria. In case of OAC reacted with 45DCOPDA it showed an activity with only gram -ve bacteria and was ranked the least among the three compounds. However this could be considered as an advantage of specific antibacterial functionality of this compound against E.coli which caused a lot of common infection.

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