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Alcohol Molecules (alcohol + molecule)
Selected AbstractsDPPH (=,2,2-Diphenyl-1-picrylhydrazyl,=,2,2-Diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl) Radical-Scavenging Reaction of Protocatechuic Acid Esters (=,3,4-Dihydroxybenzoates) in Alcohols: Formation of Bis-alcohol AdductHELVETICA CHIMICA ACTA, Issue 4 2006Shizuka Saito Abstract Protocatechuic acid esters (=,3,4-dihydroxybenzoates) scavenge ca. 5,equiv. of radical in alcoholic solvents, whereas they consume only 2,equiv. of radical in nonalcoholic solvents. While the high radical-scavenging activity of protocatechuic acid esters in alcoholic solvents as compared to that in nonalcoholic solvents is due to a nucleophilic addition of an alcohol molecule at C(2) of an intermediate o -quinone structure, thus regenerating a catechol (=,benzene-1,2-diol) structure, it is still unclear why protocatechuic acid esters scavenge more than 4,equiv. of radical (C(2) refers to the protocatechuic acid numbering). Therefore, to elucidate the oxidation mechanism beyond the formation of the C(2) alcohol adduct, 3,4-dihydroxy-2-methoxybenzoic acid methyl ester (4), the C(2) MeOH adduct, which is an oxidation product of methyl protocatechuate (1) in MeOH, was oxidized by the DPPH radical (=,2,2-diphenyl-1-picrylhydrazyl) or o -chloranil (=,3,4,5,6-tetrachlorocyclohexa-3,5-diene-1,2-dione) in CD3OD/(D6)acetone 3,:,1). The oxidation mixtures were directly analyzed by NMR. Oxidation with both the DPPH radical and o -chloranil produced a C(2),C(6) bis-methanol adduct (7), which could scavenge additional 2,equiv. of radical. Calculations of LUMO electron densities of o -quinones corroborated the regioselective nucleophilic addition of alcohol molecules with o -quinones. Our results strongly suggest that the regeneration of a catechol structure via a nucleophilic addition of an alcohol molecule with a o -quinone is a key reaction for the high radical-scavenging activity of protocatechuic acid esters in alcoholic solvents. [source] Pervaporation separation of sodium alginate/chitosan polyelectrolyte complex composite membranes for the separation of water/alcohol mixtures: Characterization of the permeation behavior with molecular modeling techniquesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Sang-Gyun Kim Abstract Polyelectrolyte complex (PEC) membranes were prepared by the complexation of protonated chitosan with sodium alginate doped on a porous, polysulfone-supporting membrane. The pervaporation characteristics of the membranes were investigated with various alcohol/water mixtures. The physicochemical properties of the permeant molecules and polyion complex membranes were determined with molecular modeling methods, and the data from these methods were used to explain the permeation of water and alcohol molecules through the PEC membranes. The experimental results showed that the prepared PEC membranes had an excellent pervaporation performance in most aqueous alcohol solutions and that the selectivity and permeability of the membranes depended on the molecular size, polarity, and hydrophilicity of the permeant alcohols. However, the aqueous methanol solutions showed a permeation behavior different from that of the other alcohol solutions. Methanol permeated the prepared PEC membranes more easily than water even though water molecules have stronger polarity and are smaller than methanol molecules. The experimental results are discussed from the point of view of the physical properties of the permeant molecules and the membranes in the permeation state. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2634,2641, 2007 [source] Supramolecular control of spin-crossover phenomena in lipophilic Fe(II)-1,2,4-triazole complexesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2006Keita Kuroiwa Abstract The spin-crossover properties of lipophilic, supramolecular Fe(II) complexes bridged by 4-(3-dodecyloxy)propyl-1,2,4-triazole [Fe(II)(1)3Cl2] were investigated in chloroform and cast films. A purple low-spin (LS) complex in a powdery form was transformed into pale yellow high-spin (HS) polymers by dissolution in chloroform. The formation of lipophilic molecular wires in chloroform was observed with transmission electron microscopy. The casting of chloroform solutions onto solid supports produced purple, transparent films (LS state). The cast films exhibited sluggish spin-crossover (LS , HS) behavior without thermal hysteresis. On the other hand, the cocasting of equimolar dodecanol or tetradecanol with Fe(II)(1)3Cl2 produced composite films in which alcohol molecules were bound to the complex by ionic hydrogen bonding (ROH···Cl,) and van der Waals interactions. At room temperature, the cast films exhibited regular lamellar structures before and after alcohol doping; this was confirmed by wide-angle X-ray diffraction measurements. Interestingly, the Fe(II)(1)3Cl2/CnOH (n = 12 or 14) ternary films showed a reversible abrupt spin crossover accompanied by thermal hysteresis. The observed bistability was related to dynamic structural transformations between lamellar and hexagonal structures. This study provides a novel supramolecular approach to designing spin-crossover polymer films with controlled thermal bistability. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5192,5202, 2006 [source] | ||||||||||