Dextrinization hydroxyl groups

Only the hydrophobic and steric terms were involved in these equations. There are a few differences between these equations and the corresponding equations for cyclo-dextrin-substituted phenol systems. However, it is not necessarily required that the mechanism for complexation between cyclodextrin and phenyl acetates be the same as that for cyclodextrin-phenol systems. The kinetically determined Kj values are concerned only with productive forms of inclusion complexes. The productive forms may be similar in structure to the tetrahedral intermediates of the reactions. To attain such geometry, the penetration of substituents of phenyl acetates into the cyclodextrin cavity must be shallow, compared with the cases of the corresponding phenol systems, so that the hydrogen bonding between the substituents of phenyl acetates and the C-6 hydroxyl groups of cyclodextrin may be impossible. 

P-Cyclodextrins chemically modified cyclo-dextrins, including fatty acid chains grafted to hydroxyl groups... 

Formic acid appears to show some selectivity in preferentially esterifying primary hydroxyl groups. Traquair161 describes the preparation of unstable starch formates. The monoformate is believed to be esterified at position 6. The periodate oxidation of monoformates of starch and limit dextrin indicates that ester linkage is predominantly... 

Fig. 18.7a-e. Cyclic and chain-like hydrogen-bonding patterns O-H- -O observed in a a-cyclo-dextrin-6H20, form I b a-cyclodextrin 6 H20, form II , intramolecular c,d,e a-cyclodextrin-7.57 H20. Infinite homodromic chains are marked chain, and cycles are indicated by round arrows with one (homodromic) and two (antidromic) heads. Only atoms of water molecules and of hydroxyl groups are drawn, the former denoted by W and the latter by the nomenclature described in Fig. 18.1. Each of the pictures a to e shows only a section of the respective crystal structure [78, 109, 575]...

Urethane-forming reaction between isocyanate and hydroxyl group was utilized by Osakada et al. to prepare polyurethane-cyclodextrin pseudoro-taxanes (Scheme 15) [86]. Polyaddition of a diol and MDI in the presence of permethylated a-cyclodextrin or permethylated (5-cyclo dextrin was carried out in DMF for 20 h at 120 °C to yield the pseudopolyrotaxane. The molar... 

Polysaccharides Hydrogen bonds and dipole-dipole interactions with hydroxyl groups of the sugar molecules are assumed to be the main interactions. In some cases, the helical structure of dextrins might be responsible for chiral recognition. Heparin, dextran sulfate, dermatan sulfate, streptomycin sulfate, amylose, chondroitin sulfate C, laminaran, dextrin sulfopropyl, and kanamycin sulfate. Doxylamine, laudanosine, naproxen, oxamniquine, pheniramine, primaquine, timepidium, trimetoquinol, etc. 

Stronger oxidation leads to oxidation of the C-6 atoms to carboxyl groups, as well as of the hydroxyl groups on the C-1, C-2, and C-3 atoms. " Only oxidations useM in dextrinization are considered here. Oxidized starches yield darker dextrins. More-advanced discussion ofthe problems of starch oxidation is given in the Radley monograph. ... 

When coupled, with cooling, with phenylhydrazine, the periodate-oxidized polysaccharides containing two or more adjacent hydroxyl groups (for example, cellulose, starch, dextrin, and dextran) yield bright-yellow phenyl-hydrazones within a few minutes. ... 

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