Reactant adsorption in differential pulse polarography: Effects of adsorptive depletion of reactant,non-linear adsorption isotherms and uncompensated resistance

Digital simulation techniques are applied to the diagnosis of the ways in which the peak currents and wave shapes of differential pulse polarograms are affected by the adsorption of reactants or products. The changes in the polarograms introduced by the items mentioned in the title are examined and their magnitudes calculated and compared with experimental polarograms. Some implications of the results in analytical applications of differential pulse polarography are described.     

Micromechanisms of failure in short-fiber-reinforced high-impact polystyrene under tensile loading

Injection-molded, short-glass-fiber-reinforced high-impact polystyrene was investigated under uniaxial tension with special attention to the effects of fiber and rubber concentration on fracture behavior. According to a fracture morphology study performed by polarized optical and scanning electron microscopy, crazes were consecutively initiated from rubber-styrene composite particles and from fiber ends. The rubber particles exhibited an intra-particle failure mode which resulted from the failure manner of the matrix becoming of a more brittle character with increasing fiber fraction. Fibers were surrounded by neigh boring growing crazes. Failure at the fiber-matrix interfaces proceeded with an increase in the number of crazes. With increasing concentration of the fibers, crazing at rubber particles appeared to be suppressed and crazing occurred more preferentially at the fiber ends, which accelerated a macroscopic fracture.Dedicated to Prof. H. H. Kausch on the occasion of his 60th birthday.     

Solvatochromic studies of interactions between surfactants and poly(N-substituted acrylamide)s

Interactions between poly(N-substituted acrylamide)s and surfactants, such as sodium dodecyl sulfate (SDoS) and sodium decyl sulfate (SDeS), in aqueous solutions were investigated using a solvatochromic probe. The polymers used were poly(N,N-dimethylacrylamide) (PDMA), poly(N-isopropylacrylamide) (PIPA), poly(N-acryloylpyrrolidine) (PAPR), and poly(vinylpyrrolidone) (PVPy) for comparison. They were labeled with pyridinium dicyanomethylide chromophore as a solvatochromic probe, and the changes in the microenvironment polarity of the polymer upon association with surfactant micelles were investigated by monitoring the λ_max in the absorption spectra of the probe molecule. It was found that the Gibbs free energy of micelle stabilization by polymer complexation for SDoS is 7.6, 4.1, and 2.2 kJ mol⁻¹, and for SDeS 5.1, 2.9, and 0.8 kJ mol⁻¹ with PIPA, PAPR, and PDMA, respectively. These results indicate that the complexation between polymer and surfactant is influenced not only by the alkyl-chain length of the surfactant, but also by the polymer side groups.     

Direct conversion of allylic alcohols into N-acyl-α-amino acids by catalytic amidocarbonylation by means of homogeneous binary systems

N-Acyl-α-amino acids are synthesized by the amidocarbonylation of allylic alcohols catalyzed by homogeneous binary systems which consist of cobalt carbonyl and rhodium (or iron or palladium) complexes.     

Total synthesis of tylosin

Tylosin has been synthesized byregio- and stereoselective introduction of the amino disaccharide moiety and D-mycinose onto the previously synthesized 16-membered-ring aglycone.     

A novel method for preparation of 2-(methyl- or phehnylthio)alkanoic esters

Ethyl 2-acetylalkanoate gave ethyl 2-(methyl- or phenylthio)alkanoate in high yield on treatment wiht CH₃SSO₂CH₃, PhSSO₂Ph, or PhSSPh in the presence of small excess of EtONa in EtOH. Application of the present method to synthesis of pellitorine and the queen substance is also described.