Uber symmetrische Functionen von mehreren Reihen von Veränderlichen

Ohne Zusammenfassung     

Bei der W?gung von Niederschl?gen auf getrockneten Filtern

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Nachweis von Anilin, Acetanilid und Paramidophenol im Harn

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Hydrogen Bonds in Rubidium Amide‐Ammonia(3/2), RbNH2·2/3NH3

Rubidium amide‐ammonia(3/2), RbNH₂·2/3NH₃, was synthesized from Rubidiumhydride, RbH, in liquid ammonia at ?78 °C. The compound crystallizes in the cubic space group I2₁3 with Z = 4, a = 10.0490(12) Å, and V = 1014.77(20) Å as isometric colorless crystals. The crystal structure was solved from single‐crystal X‐ray data. The structure contains a three‐dimensional network of amide anions and ammonia molecules, which are interconnected via hydrogen bonds.     

Janus Effect of Lewis Acid Enables One-Step Block Copolymerization of Ethylene Oxide and N-Sulfonyl Aziridine

One-step sequence-selective block copolymerization requires stringent catalytic control of monomers relative activity and enchainment order. It has been especially rare for A_nB_m-type block copolymers from simple binary monomer mixtures. Here, ethylene oxide (EO) and N-sulfonyl aziridine (Az) compose a valid pair provided with a bicomponent metal-free catalyst. Optimal Lewis acid/base ratio allows the two monomers to strictly block-copolymerize in a reverse order (EO-first) as compared with the conventional anionic route (Az-first). Livingness of the copolymerization facilitates one-pot synthesis of multiblock copolymers by addition of mixed monomers in batches. Calculation results reveal that a Janus effect of Lewis acid on the two monomers is key to enlarge the activity difference and reverse the enchainment order.     

Ueber Dr. C. Noellner's Salpeters?urebestimmung

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Influence of water on localized and delocalized molecular mobility of cellulose

The influence of hydration on cellulose molecular mobility is investigated by two dielectric methods at different molecular scale. The mobility of side groups, assigned to γ mode, for dried cellulose increases. The water molecules have an anti-plasticizer effect on γ mode due to the water–polymer hydrogen bonding. For the β relaxation mode, only observed by the Thermo Stimulated Current technique, the hydration plays a role of plasticizer. The α relaxation mode assigned to the delocalized cooperative mobility of long chain segments of cellulose is plasticized by water. The study of activated parameters deduced from fractional polarization procedure, shows an increase of the activation enthalpy range with dehydration. It permits to conclude that reduction of hydrogen bonds density leading to a more extended cooperative mobility.