Basically, ceric ion, a strong oxidizing agent, could oxidize pyranose ring of starch to produce free starch macro-radical ([Ce.sup.4+] + Starch [right arrow][Ce.sup.3+] + Starch* [H.sup.+]), followed by the graft polymerization of VAc monomer via chain polymerization to form starch-g-PVAc graft copolymer.
la) include absorption peaks of O--H (3700-3100 [cm.sup.-1]), C-H (2925 and 2887 [cm.sup.-1]), O-H bending of absorbed water (1649 [cm.sup.-1]), C--O-- stretching (1155-1000 [cm.sup.-1]) and the skeletal vibration of pyranose ring (935, 851, 761, 579, and 536 [cm.sup.-1]) [32, 33], As shown in Fig.
The char yield of starch is essentially high, up to 12.2%, attributing to the pyranose ring structure in the common carbohydrate compound.
This clearly indicates the slight distortion of the pyranose ring
from regular [sup.1][C.sub.4] conformation as shown in the Figure 1.
3B) is assigned to the first overtone of the fundamental CH stretching vibrational mode and is due to the furanose or pyranose ring (invariable constituent of hemicellulose).
This is also clear from the variation in the peak position of the infrared band markers at 1580 nm (crystalline region in cellulose), 1705 nm (aromatic skeletal in ligin) and 1773 (furanose or pyranose ring constituent of hemicellulose) at different temperatures.
From the first come seven papers exploring conformational dynamics of oligosaccharides, structure and dynamics of carbohydrates using residual dipolar couplings, combined theoretical and NMR (nuclear magnetic resonance) experimental approach on carbohydrate-aromatic interactions and on pyranose ring
distortion, laser photo chemically induced dynamic nuclear polarization technique as a tool for structural analysis of inter- and intramolecular protein-carbohydrate interactions, and hydroxy protons in structural studies of carbohydrates by NMR spectroscopy.
Electronegative substituents at the C-2 position of saturated heterocycles or at the anomeric carbon of a pyranose ring
favor the equatorial position much less than expected; often the axial position is favored.
The ABX systems at 2.24 and 1.84 ppm were assigned to the pyranose ring
protons of carbon-3 of the [beta] anomer.
This increasing redox potential reflects the electron withdrawing properties of heterocyclic pyranose rings
. The diffusion coefficient and heterogeneous rate constant directly predict that how electrochemically active molecules diffuse towards the electrode interfaces during the redox process.
In addition, chitosan has reactive amino groups on pyranose rings
and becomes a cationic polymer upon the protonation of its amino groups.