Preparation of optically active 1-acetoxy-2-aryloxypropionitriles and its application to a facile synthesis of (S)-(−)-propranolol

(S)-1-acetoxy-2-aryloxypropionitriles were synthesized by an asymmetric hydrolysis of the racemates with an enzyme. (S)-propranolol, a typical β-adrenergic blocker, was synthesized from (S)-1-acetoxy-2-α-naphthyloxypropionitrile in two steps.     

Measurement of atmospheric NO2 column density with kitt peak solar flux atlas as a reference

The vertical column abundance of NO₂ is measured using direct sunlight. The solar spectra in the wavelength region of 430–450 nm observed from the earth’s surface are ratioed with a reference spectrum taken from the Kitt Peak Solar Flux Atlas. The large Fraunhofer features (20–40%) are eliminated by wavelength correction, resolution matching and ratioing of observed spectra to the reference. The retrieved values of the NO₂ vertical column density are in a range of (2–15)x10¹⁶ molecules/cm² with an accuracy of better than 3%. This result demonstrates the usefulness of the Kitt Peak Atlas in the study of tropospheric NO₂ concentration, giving a standard extraterrestrial solar spectrum for the case in which the Langley method is not readily applicable.     

Environmental stress cracking of low-density polyethylene in normal alcohols

Fracture mechanics was used to investigate the environmental stress cracking of low-density polyethylene with 4.0 melt flow index. Annealed samples were prepared; a single edge notch was made and then the samples were fractured under constant load in four different liquid alcohols. The relation between the stress intensity factor K and the crack speed a˙ has been investigated. The log a˙ vs. logK curves are influenced not only by temperature but also by the alcohol used as the environment. This influence has been studied in detail. The conclusions are as follows: the crack speed at high K is determined by the diffusion mechanism, and this mechanism cannot be explained in terms of hydrodynamics but can be explained in terms of thermally activated molecular motion. On the other hand, the crack speed at low K is strongly related to the plasticization and the stress relaxation of the crack tip material.     

A comparison of the structures of Ni---Zr amorphous alloys obtained by mechanical alloying and melt spinning

The structures of mechanically alloyed (MA) and melt-spun (MS) Ni_xZr_1-x (x = 0.28, 0.33, 0.40) amorphous alloys were investigated by X-ray diffraction. The interatomic distances, r_NiZr and r_ZrZr, were calculated from the deconvolution of the principal peak of the radial distribution function (RDF) using Gaussian functions. The distances were nearly equal for the amorphous alloys of the same composition prepared by the two methods, i.e., 2.69 and 2.67 Å and 3.28 and 3.22 Å on average for the MA and MS specimens, respectively.     

Sedimentation equilibrium in nonideal heterogeneous systems. I. Fundamental equations for heterogeneous solute systems and some preliminary results

The sedimentation-equilibrium method is extended to treat nonideal solutions of heterogeneous macromolecules. The solute is assumed to be heterogeneous not only in molecular weight but also in other quantities such as partial specific volume, second virial coefficient and specific refractive increment. General expressions for various observable molecular weights, especially for weight-average, z-average, and number-average molecular weights, are derived. Their dependences on sedimentation parameter and solute concentration are discussed in detail. For the extrapolation of observable molecular weights, giving a type of weight-average, and z-average, to infinite dilution to estimate the molecular weight and the second virial coefficient, average concentration is superior as a concentration variable to original concentration. The plots of observable molecular weight versus average concentration are usually less influenced by the choice of the sedimentation parameter, especially of rotor speed. The general expressions are applied to a few special cases; monodisperse polymer, polydisperse homologous polymer, and polymer blend. The results are compared with experiments on a monodisperse, polystyrene, a polydisperse poly(methyl methacrylate), and a mixture of the two polymers, all in 2-butanone at 25°C. The agreement between the theory and experiments is satisfactory.     

Restricted rotation involving the tetrahedral carbon: XXIII—comparison of barriers to rotation of 9-(2-isopropylphenyl) fluorene obtained by 1H DNMR, 13C DNMR,double resonance and kinetic measurements

Rates of rotation about the C-9-C-ar bond of 9-(2-isopropylphenyl) fluorene were measured by ¹H DNMR, ¹³C DNMR, double resonance, and a kinetic method. The kinetic data obtained by these methods were critically examined. The DNMR methods afforded satisfactory results if rate data obtained by total line shape analyses of complicated signals with couplings were used, and those derived from simple patterns were abandoned. Agreement among the data yielded by the four different methods was excellent, provided that the data which might contain dubiously large errors were excluded.