3829between I3C CP/MAS spectra of amorphous starches and V-type amylose complexes provides evidence for the presence of amylose/lipid inclusion complexes in starch granules. adjacent to a high-energy glycosidic linkage. Apart from these signals, chemical shift ranges are similar to those of V-amyloses.Solution state C-l and C-4 chemical shifts for cu-cyclodextrin are closely matched if averages of solid-state shifts are taken which ignore the sites adjacent to the high-energy linkage. This suggests that a-cyclodextrin might adopt a more expanded conformation in solution compared to the solid state. The marked similarity Registry No. a-Cyclodextrin, 10016-20-3; a-cyclodextrin hydrate, 5 121 1-5 1-9; 8-cyclodextrin, 7585-39-9; 8-cyclodextrin hydrate, 68 168-23-0; CY-( 1-+4)glucan, 9051-96-1; amylose, 9005-82-7; starch, 9005-25-8.
Abstract:The structures of lithium 4-fluoro-, 4-chloro, 2-and 4-bromo-, 4-(trifluoromethy1)-, 4-methoxy-, 2-methyl-, 2-ethyl-, 2-n-propyl-, 2-isopropyl-, 2-tert-butyl-, 2-(methoxymethyl), 3,5-dimethyl-, 3,5-dimethyl-4-methoxy-, 4-chloro-3,5-dimethyI-, 3,5-diethyl-, and 3,5-dimethoxyphenolates in solution in weakly polar, aprotic solvents such as pyridine, tetrahydrofuran, dimethoxyethane, 1,3-dioxolane, diethyl ether, 2,6-lutidine, and triethylamine have been established by 13C NMR spectroscopy. Para substituents influence the equilibrium between dimer and tetramer through their effect on the basicity of the anion. @Alkyl substituents promote dimer formation through steric effects in the order of their steric bulk. The 2-methoxymethyl group stabilizes the tetramer. Dimers are favored relative to tetramers by a combination of high Lewis basicity and low steric demand of the solvent. A number of lithium phenolates in 1,3-dioxolane exist as hexamers at low temperatures. The following pairs of values for AH (kcal mol-I) and A S (cal mol-]