Polyiodine units in starch–iodine complex: INDO CI study of spectra and comparison with experiments

✍ Scribed by Mark Minick; Kristen Fotta; Arshad Khan

• Publisher: Wiley (John Wiley & Sons)
• Year: 1991
• Tongue: English
• Weight: 569 KB
• Volume: 31
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360310106

✦ Synopsis

The starch-iodine blue complex formation does not involve negatively charged iodine species like I,, I;, or I;; rather, neutral iodine units are involved. The heat of reaction is determined to be about -110 kJ for every mole of 1-1 unit in the amylose helix, which suggests that the dissociation of Iz (binding energy 149 kJ/mol) does not take place during the complex formation. Quantum mechanical (INDO CI) calculations indicate that the linear as well as nonlinear polyiodine units, Is, with interiodine distance of 3.0 8, are responsible for characteristic absorbance bands of the starch-iodine complex. Based on our previous article [ ( 1989) J. Polym. Sci. A 27, 41611 and the present studies we identify ( C6H1005)16.516 to be the polymeric unit responsible for the characteristic blue color of the complex.