The Correct Meaning of “Coating Efficiency” vs. the “Utilization of Theoretical Efficiency”

The correct meaning of the the term “utilization of the theoretical efficiency” vs. the “coating efficiency” is explained.     

Synthese „anorganischer”︁ Tintenfisch-Moleküle. II

Synthesis of “Inorganic” Pode-type Molecules. II The reaction of the amino compounds Me_yB? NMe₂ (B ? As, y ? 2; B ? Si, y ? 3) with 1, n-dioles results in the formation of the compounds HO(CH₂)_nOBMe_y. These compounds can be used as the arms of pode-type molecules Me_xA[? O(CH₂)_nOBMe_y]_z with A ? Si, As. The influence of A, B, n, and z in the rearrangement of these molecules is examined. A second type of pode molecules can be prepared by the reaction of Me₂As? R? OH (R ? CH₂CH₂, CH₂CH₂(OCH₂CH₂)₂) with the amino compounds Me_x(NMe₂)_z (A ? As, Si). These reactions result in the formation of molecules as Me_xA(ORAsMe₂)_z.     

Gel-permeation chromatography. V. A study of “overloading effects”

In the calculation of molecular weight averages from GPC chromatograms and in the correction for zone broadening effects, it is assumed that the retention volumes of the individual species are not affected by the presence of the other components in the sample (linear fractionation process). This assumption was tested by the computer comparisons of the chromatograms of mixtures of narrow molecular weight distribution polystyrene standards and the envelopes of the individual chromatograms of the components of the mixtures. Disagreements between experimental and computer synthesized chromatograms were interpreted as non-linear fractionation effects. The investigation covered a range of molecular weights (1.8 × 10⁶ to 2100), molecular weight distributions (binary and seven component mixtures), and sample loadings (2 to 70 mg). Accurate normalizations of raw GPC chromatograms and calculations of molecular weight averages were made possible through an automated GPC apparatus using a high-speed computer for data acquisition and data reduction. It was found that some nonlinear fractionation effects (large disagreement between chromatograms of the mixture and the computed envelopes of the individual chromatograms of the components of the mixture) became more pronounced as sample loading was increased and as the molecular weight distribution of the sample narrows. The nonlinear effect was also found to be sensitive to the molecular weight of the sample.     

Formation of spherulites in polyamides. V. “odd-odd” polyamides

The crystallization of a series of “odd-odd” polyamides has been examined for a variety of fusion conditions and crystallization temperatures. Diverse kinds of spherulites and other crystalline structures have been formed in these nylon polymers by direct crystallization from the melt and by melt-seeding techniques. The structures formed in this way have been characterized primarily with the aid of optical microscopy. In this series of polymers, characteristic textural features yield a fairly unified pattern of crystallization behavior. Crystalline aggregates are formed near the respective melting points of these polymers. In very thin sections (ca. 0.1μ), plateletlike crystals of high crystallinity exhibit optical and diffraction behavior characteristic of single crystals.     

ChemInform Abstract: The Smallest “Aurophilic Species”.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Synthesis and reactions of “biginelli-compounds”. Part I

Various reactions of 2-oxo(or thioxo)-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid derivatives (Biginelli-compounds) were investigated. The site of methylation and acylation on 6-methyl-4-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid ethyl ester 1a and its 2-oxo derivative 9a was studied. The synthesis of pyrimido[2,3-b]thiazines and thiazolo[3,2-a]pyrimidines was accomplished by condensation of 1a with 1,3-and 1,2-dielectrophiles. A Dimroth-like rearrangement yielding 6H-1,3-thiazines can be observed when 1a was treated with dimethylformamide and phosphorus oxychloride. The formation of indeno[1,2-d]pyrimidines can be achieved by intramolecular Friedl-Crafts acylation of 9a and 13 , respectively. Finally a route for the preparation of 4,6-disubstituted-pyrimidine-5-carbonitriles is presented, starting with Biginelli-compound 25 .