Nbcl Synthesis Lab Report

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3. Results and discussion
4-Chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) is an activated aryl halide that has been used as a chromogenic and fluorogenic reagent for the determination of many drugs with primary and secondary amino groups [22-24]. The reaction of NBD-Cl with LBT has not been investigated yet. LBT contain secondary amino group which can react with NBD-Cl in alkaline medium to form a yellowish green colored product. This derivative exhibited maximum fluorescence intensity at 540 nm after excitation at 476 nm (Figure 2), the maximum absorbance of the reaction product was measured at 480 nm (Figure 3).
3.1. Optimization of the reaction conditions
The experimental parameters affecting the development and stability of the reaction product between the drug and the reagent were investigated and optimized. Each parameter was changed individually while the others were kept constant. These parameters include; pH, buffer (type & volume), concentration of NBD-Cl, reaction and stability time, temperature, acidification and diluting solvent.
3.1.1. Effect of pH
The effect of the solution pH on the reaction product formation was studied in the pH range of 6.5– 9.5 using Clark
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Equimolar solutions of both the drug and NBD-Cl reagent (1×10-3 M) and (1×10-2 M) were prepared for method I and method II respectively. Then portions of mixture of master solutions of the drug and reagent were mixed comprising different complementary proportions. Either the relative fluorescence intensity or the absorbance were measured. A blank experiment was carried out simultaneously. The stoichiometry between the drug and NBD-Cl reagent by both methods as shown in Figure 8, it is clear that the ratio is 1:1. Based on this ratio the suggested mechanism of the condensation reaction with NBD-Cl was presented in Scheme

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