Polymerization of 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose and 1,2-O-isopropylidene-α-D-glucofuranose

A new method for preparing D -glucose polymers is described. Isopropylidene derivatives of D -glucofuranose, particularly the 1,2-mono-O-derivative, are treated with Lewis acids, such as boron trifluoride, to eliminate acetone and produce a highly branched polymer with a molecular weight of 12,700. Approximately one isopropylidene unit remains, possibly on the potential reducing end of the glucan. Up to 95% of the polymer units are D-glucopyranoside units indicating that ring expansion occurs during the condensation.     

Bestimmung der zitratl?slichen Phosphors?ure in Superphosphaten

Ohne Zusammenfassung     

A Comparison of Two Variational Methods

A discussion is given of the relation between the maximum functionaltheorem and Schwinger's variational principle, and it is shownthat the bound given by Schwinger's principle is better thanor the same as that given by the maximum functional theorem.     

Effects of Poly(Ethylene Glycol) on the Physical Properties of Blended Molecules of Starch and Poly(Ethylene-co-Acrylate,Ammonium Salt)

Abstract

A mixture of starch (36%) poly(ethylene-co-acrylate, ammonium salt) (41%), water (12.5%), urea (8.4%), and poly(ethylene glycol) (M _n 4600) (2.1%) were converted to plastic test pieces by extruding (130°C), drying and grinding (25°C), and hot pressing (175°C). After equilibration at ?50% relative humidity and 25°C, the test pieces contained 3.5–4.6% moisture and 2.3% poly(ethylene glycol) (PEG). Among wheat, corn, potato, and rice starches, the wheat starch (WS) blend showed the highest Young's modulus (181.3 MPa), whereas the corn starch (CS) blend had a modulus and elongation that almost matched those of lowdensity polyethylene. When PEG was eliminated from the WS formulation, tensile strength remained constant, but Young's modulus doubled. The modulus decreased continually as test pieces absorbed water up to 27% moisture, but elongation and argon laser light transmittance were optimum at ?12% moisture. Differential scanning calorimetry indicated that PEG formed a solid inclusion complex with amylose upon drying at 60°C, but no complex was detected in dilute alkali by optical rotation.     

Acid-catalyzed polymerization of 1,6-anhydro-β-D-glucopyranose

A number of 1,6-anhydrides were polymerized in the melt at 115°C by use of monochloroacetic acid as catalyst. In the early stages of polymerization (up to 40–50% monomer consumed), each monomer was found to disappear by a first-order rate process. The 1,6-anhydrides investigated and their relative rates of polymerization were: 1,6-anhydro-2-O-methyl-β-D -glucopyranose, 1.0; 1,6-anhydro-3,4-di-O-methyl-β-D -glucopyranose, 1.4; 1,6-anhydro-2-O-methyl-β-D -galactopyranose, 2.3; 1,6-anhydro-3-O-methyl-β-D -glucopyranose, 2.6; 1,6-anhydro-4-O-methyl-β-D -glucopyranose, 6.3; 1,6-anhydro-4-O-(β-D -glucopyranosyl) β-D -glucopyranose, 9.0; 1,6-anhydro-β-D -galactopyranose, 17; 1,6-anhydro-β-D -glucopyranose, 37; 1,6-anhydro-β-D -mannopyranose, 91; and 1,6-anhydro-2-deoxy-β-D -arabino-hexopyranose, 240. The effect of substitution on the rate of polymerization suggests this reaction is mechanistically related to the acid hydrolysis of pyranosides. The results suggest that polymerization proceeds in two stages: (1) an initial build-up of dimer followed by (2) a slower growth to higher molecular weight material.     

Synthesis and X-ray crystal structure determination of the first Copper(II) complexes of tetraazamacrocycle-glyoxal condensates

Novel Cu(II) complexes CuLCl(2) (L = 1-4) have been synthesized containing the metal bound to a well-known type of tetracyclic bisaminal formed from the condensation of glyoxal and tetraazamacrocycles (1 = cyclam-glyoxal condensate, 2 = [13]aneN4-glyoxal condensate, 3 = cyclen-glyoxal condensate, 4 = isocyclam-glyoxal condensate). The four-coordinate complexes were characterized by X-ray crystallography, electronic spectroscopy, solid-state magnetic moments, and electron spin resonance spectroscopy. The tetracyclic bisaminals, although having four potential donor atoms, are bound in a cis-bidentate fashion to Cu(II) with two additional cis-chloride donors. The ligands take up folded conformations, and with the exception of ligand 4, only nonadjacent nitrogen atoms coordinate. As expected, ligand 2 in Cu(2)Cl(2) has a folded structure similar to those of the previously characterized 1 and 3. The conformation of 4 in the complex Cu(4)Cl(2) differs from 1-3 in that three nitrogens direct their lone pairs to one side of the folded tetracycle, with adjacent nitrogen atoms coordinated to Cu(II). This difference is probably caused by the presence of the more flexible seven-membered ring rather than the five- to six-membered rings in 1-3. Air oxidation of Cu(I) in the presence of 1 or 3 results in bis(mu-hydroxo) dimers as characterized by X-ray crystal structures, suggesting dioxygen binding, followed by O-O bond splitting to give the Cu(2)O(2) diamond core.