Biopolymer (Chitin) from Various Marine Seashell Wastes: Isolation and Characterization

Published ArticleChitin has been produced from different sea waste sources including, molluscs (mussel and oyster shell), crustacean (prawn and crab) and fish scale (pang and silver scales) using deproteinization and demineralization as chemical methods. The conditions of chemical extraction process determine the quality of chitin. The obtained results revealed that, about 1 and 10% HCl and NaOH were adequate concentrations for deproteinization and demineralization process respectively. Chitin from oyster and crab shell waste had the highest yield of 69.65 and 60.00% while prawn, mussel shell, pang and silver scales had the lowest yield of 40.89, 35.03, 35.07 and 31.11% respectively. Chitin solubility is controlled by the quantity of protonated acetyl groups within the polymeric chain of the chitin backbone, thus on the percentage of acetylated and non-acetylated d-glucos-acetamide unit. Good solubility results were obtained in mussel, oyster and crab shells respectively. The chitin molecular weight characteristics and activity are controlled by the degree of acetylation (DA) and the distribution of acetyl group extending in the polymer chain. DA is determined by acid-base titration methods and molecular weight determined by Brookfield viscometry. Both methods are found to be effective

Synthesis and Kinetics of Sterically Altered Photochromic Dithizonatomercury Complexes

Following a previous study where 12 electronically altered dithizones were synthesized, here we report on attempts to synthesize 26 dithizones. The purpose was to explore the boundaries within which dithizones may be synthesized, explore spectral tuning possibilities, and investigate steric effects on the photochromic reaction of its mercury complexes. Contrary to expectation, large substituents like phenoxy groups increased the rate of the photochromic back-reaction. In the series H-, 2-CH₃-, 4-CH₃-, 3,4-(CH₃)₂-, 2-OC₆H₅-, and 4-OC₆H₅-di­thizon­ato­phenyl­mercury­(II), the lowest rate of 0.0004 s^–1 was measured for the 2-CH₃ complex, while the rate for the 2-OC₆H₅ derivative was 20 times higher. A solvent study revealed a direct relationship between dipole moment and the rate of the back-reaction, while the relationship between temperature and rate is exponential, with <i>t</i>_1/2 = 2 min 8 s for the 4-phenoxy complex. The crystal structures of two dithizone precursors, 2-phenoxy- and 4-phenoxy­nitro­formazan, are reported