Beitrag zur Frage der qualitativen und quantitativen Bestimmung einiger Pyridinderivate mit Hilfe der IR-Absorptionsspektroskopie

Zusammenfassung Es wird die Möglichkeit einer qualitativen und quantitativen Reinheitsprüfung mit Mitteln der IR-Absorptionsspektroskopie an einer Anzahl von Pyridinderivaten untersucht. Zu diesem Zweck werden die IR-Absorptionsspektren der reinen Substanzen, sowie von binären und ternären Gemischen aufgenommen. Die Spektren werden aus-gewertet und die Nachweisgrenzen angegeben.Dem Verband der Chemischen Industrie und der Deutschen Forschungsgemeinschaft danken wir für die Unterstützung dieser Arbeit.     

Intramolecular homolytic substitution at selenium: synthesis of novel selenium-containing vitamin E analogues

Treatment of 1-(benzylselenenyl)-5-butyl-5-nonanol (10) with oxalyl chloride followed by the sodium salt of N-hydroxypyridine-2-thione afforded the corresponding pyridine-2-thione-N-oxycarbonyl (PTOC) oxalate ester which was not isolated but immediately heated to provide 2,2-dibutylselenane (7). This transformation presumably involves a tertiary alkyl radical that undergoes intramolecular homolytic substitution at selenium with loss of the benzyl radical to provide the selenium-containing ring system (7). A similar protocol, when applied to 1-(2-benzylselenenyl-5-methoxyphenyl)-3-methyl-3-heptanol (18) and 1-(2-benzylselenenyl-5-methoxyphenyl)-3,7,11,15-tetramethyl-3-hexadecanol (19), followed by deprotection, afforded the selenium-containing alpha-tocopherol analogues 4 and 1f, respectively, in moderate yields. To the best of our knowledge, these transformations represent the first examples of tertiary radicals involved in homolytic substitution chemistry at selenium.     

Hydrophobicity and counterion effects on the binding of ionic surfactants to uncharged polymeric hydrogels

Gel swelling experiments have been used to study the binding of ionic surfactants to a series of nonionic alkylacrylamide hydrogels of increasing hydrophobicity. The binding of hexadecyl trimethylammonium (C16TA+) to uncharged gels is sensitive to both the hydrophobicity of the gel and the counterion to the surfactant. There is a minimum hydrophobicity threshold below which binding of the surfactant does not occur, and this is influenced by the counterion to the surfactant. The surfactant concentration at the onset of binding, the critical association concentration (cac), decreases with increasing gel hydrophobicity. The maximum swelling of the gel (at intermediate network hydrophobicity) increases in the order of the Hofmeister series of anions, bromide (Br-) < chloride (Cl-) < acetate (Ac-). At higher gel hydrophobicity, differences in swelling are no longer observed on changing the counterion. A minimum hydrophobicity threshold was also found for the binding of the anionic surfactants sodium dodecyl sulfate (SDS) and sodium dodecyl-di(ethylene oxide)-sulfate (SD-(EO)2-S). Differences in the swelling behavior with network hydrophobicity are explained in terms of the degree of saturation of the gel with surfactant at the cmc.     

Electron-rich radicals by neutralizationreionization mass spectrometry. Generation, dissociations and energetics of the hydrogen atom adduct to acetamide

Protonated acetamide exists as two planar conformers, the more stable anti-form (anti-1(+)) and the syn-form (syn-1(+)), DeltaG(degree) (298) (anti-->syn) = 10.8 kJ mol(-1). Collisional neutralization of 1(+) produces 1-hydroxy-1-amino-1-ethyl radicals (anti-1 and syn-1) which in part survive for 3.7 micros. The major dissociation of 1 is loss of the hydroxyl hydrogen atom (approximately 95%) which is accompanied by loss of one of the methyl hydrogen atoms (approximately 3%) and loss of the methyl group (approximately 2%). The most favorable dissociation of the OH bond is calculated to be only 34 kJ mol(1) endothermic but requires 88 kJ mol(-1) in the transition state. Other dissociations of 1, e.g., loss of one of the amide hydrogens, methyl hydrogens, and loss of ammonia are calculated to proceed through higher- energy transition states and are not kinetically competitive if proceeding from the ground doublet electronic state of 1. The unimolecular dissociation of 1 following collisional electron transfer is promoted by large Franck-Condon effects that result in 8090 kJ mol(-1) vibrational excitation in the radicals. Radicals 1 are calculated to exoergically abstract hydrogen atoms from acetamide in water, but not in the gas phase. The different reactivity is due to solvent effects that favor the products, (.)CH(2)CONH(2) and CH(3)CH(OH)NH(2), over the reactants.     

Homomorphisms on some function algebras

In this note we prove, for some classes of real locally convex spacesE including all complete Schwartz spaces, that every non-zero homomorphism on the algebraC (E) ofC -functions onE is given by a point evaluation at some point ofE.