Polymeric complexes of cornstarch and waxy cornstarch phosphates with milk casein and their performance as biodegradable materials

Complexes of phosphated cornstarch and waxy cornstarch with casein were prepared and characterised. They were prepared from casein in defatted milk and corn and waxy corn starches phosphated to degree of substitution values (DS) of 0.0637 and 0.0968, respectively. The components were blended in starch to casein ratios of 2:1, 1:1, and 1:2, then precipitated with hydrochloric acid. Aqueous solubility, water binding capacity, IR spectra, and thermal analysis (thermogravimetry, TG, and differential thermogravimetry, DTG) of the precipitates revealed that they were not simple physical mixtures of the components. The components interact with one another electrostatically with involvement of the starch phosphate groups and the peptide bonds of casein as documented by the IR spectra. Because of their insolubility in 7 M aqueous urea solution they might also be considered as complexes in which the components were chemically bound. Enzymatic studies showed that they are biodegradable materials.     

Aggregation behavior and chromonic liquid crystal phase of a dye derived from naphthalenecarboxylic acid

Polarizing microscopy, X-ray scattering, and absorption spectroscopy are used to investigate the aggregation process and chromonic liquid crystal of the anionic compound Bordeaux dye, a product of the sulfonation of the dibenzimidazole derivative of naphthalenetetracarboxylic acid. Polarizing microscopy reveals that the liquid crystal phase forms at room temperature when the concentration is only about 6 wt%, a value lower than what is found in many aggregating systems. The X-ray results indicate that the aggregation is via columns, with a cross-sectional area about 2.5 times larger than the individual molecule. Absorption spectroscopy shows a significant change in the absorption spectrum due to aggregation, which is nicely explained by a simple theory of isodesmic aggregation and excitonic coupling between the molecules in an aggregate. The "stacking free energy change" for a molecule in an aggregate relative to a molecule in solution is estimated to be about 9 kBT, a larger value than that found in the one other system where it has been estimated.     

Complexes of 3.6 kDa maltodextrin with some metals

Preparation of magnesium, lanthanum, and bismuth(III) complexes of 3.6 kDa maltodextrin and some properties of the resulting materials are presented. The metal derivatives contain metals bound to the oxygen atoms of the hydroxyl groups of maltodextrin. Additionally, the metal atoms are coordinated to the hydroxyl groups of the D-glucose units of the macroligand. Such coordination stabilized the metal - oxygen bond against hydrolysis, even in boiling water. The presence of magnesium and lanthanum atoms increased the thermal stability of maltodextrin, whereas bismuth atoms decreased it.     

Exposure of granular starches to low-pressure glow ethylene plasma

Polymerization of ethylene was initiated by low-pressure glow plasma generated in this gas. Depending on starch present in this plasma polymerization could be considered either as graft-polymerization of ethylene onto starch or homopolymerization. Result of the treatment of cassava, corn, potato, rice Indica, sweet potato, and waxy corn starches with ethylene plasma was analyzed by means of high-performance size exclusion chromatography, X-ray powder diffraction, thermogravimetry, digestion with β-amylase, and scanning electron microscopy. Analyses suggested that graft-polymerization occurred on sweet potato and rice starch. With other starches homopolymerization of ethylene on granules took place.     

Tautomerism and Rotamerism in 2-(2-Phenylhydrazino)pyridine

The title compound is shown by X-ray crystallography and NMR spectroscopy to exist both in the solid state and in solution as such. Deuterium-induced shifts confirm the phenylamino structure for 2-phenylaminopyridine.     

Re-examination of Nucleophilic Substitutionin Chlorokojic Acid

Summary.  Chlorokojic acid was reacted with S₂O₃ ²⁻, NO₃ ⁻, N₃ ⁻, I⁻, and SCN⁻. Only the three latter nucleophiles substituted the chlorine atom in the 2-CH₂Cl group of kojic acid. In none of the products nucleophilic substitution at position 6 of the 4-pyrone could be found. Regular substituion of chlorokojic acid with I⁻ (iodokojic acid), N₃ ⁻ (azidokojic acid), and SCN⁻ (thiocyanato and isothiocyanato kojic acids) was accompanied by formation of allomaltol. Reaction pathways for the formation of allomaltol and 6-substituted allomaltol derivatives are proposed. The latter has been formerly discovered in the reaction of chlorokojic acid with secondary amines. Received October 10, 1999. Accepted (revised) November 25, 1999     

Monoexcited singlet states and conformation of some acylpyridines

Substituent effects on the UV-spectra of formyl-, acetyl- and benzoylpyridines are investigated. The UV-bands are discussed by comparison with the calculated energies and oscillator strengths of all planar and twisted 2-acyl-, 3-acyl- and 4-acyl derivatives using the SCF CI-1 method. The structure of each ¹π^* ← ¹π transition is determined from the contributions of the individual MO transitions and their LCAO characteristics. The conformation of acylpyridines is discussed.     

Drift Mobility of Electrons in Pyrazoline-Containing Copolymers

Drift mobility of electrons in copolymers containing pyrazolyl fragment in the main or side chain of the copolymer is studied experimentally using the time-of-flight method. The mobility is an exponential function of the applied electric field, and its values for the copolymers range from 5 × 10^–7 to 2 × 10^–5 cm² V^–1 s^–1 at the field strength ranging from 5 × 10⁴ to 1 × 10⁶ V cm^–1. Based on the measured mobilities and the molecule parameters, which were obtained by a PM3 quantum-chemical calculation, the role of copolymer fragments in the transport of charge carriers is discussed.     

α-Hydroxylation of ketones: Osmium tetroxide/N-methylmorpholine-N-oxide oxidation of silyl enol ethers

Osmium tetroxide/N-methylmorpholine-N-oxide oxidation of silyl enol ethers, derived from ketones with either kinetic or thermodynamic regiochemical control, produces α-ketols in good to excellent yields.