Thin-layer chromatography of steroisomeric 2,4-dinitrophenylhydrazones of aliphatic aldehydes.
Abstract The stereoisomeric forms of 2,4-dinitrophenylhydrazones (2,4-DNP) of some aliphatic aldehydes and unsymmetrical detones were separated by several reverse phase thin-layer chromatographic procedures. Evidence indicated that the reaction to produce the 2,4-DNP produces both the syn and anti form, but that repeated recrystallization in ethanol yielded the pure syn crystalline form. Racemizaton of the crystalline syn form could be stimulated by dissolving it in chloroform or by the addition of a small amount of hydrochloric acid to an acetone or methanol solution. Certain thin-layer chromatographic systems separated the homologous series to the greatest extent and the isomers the least (undecane/75% methanol-25% water). Another system separated the isomers to a considerable extent but was not too effective in separating the homologous series (dimethylformamide/heptane). Combinations of these systems should be of value in resolving mixtures of syn and anti forms of mixtures of aliphatic aldehyde 2.4-DNP.
Über Carbonylverbindungen beim Tollenser (Tilsiter) Käse
Es wird das Auftreten von neutralen Monocarbonylverbindungen (Aldehyden und Methylketonen) wahrend der Reifung von Tollenser Kase untersucht und deren Bedeudung fur sein Aroma diskutiert. Nachgewiesen werden Acetaldehyd, Aceton und Methylathylketon (je etwa 2,5–5,0 mg/kg Kase) sowie in geringerer Menge Methylpropyl-, Methylbutyl- und Methylpentylketon (je etwa 0,5 mg/kg) Eine Zunahme dieser Verbindungen wahrend der Reifung erfolgt nicht, so das eine Beteiligung dieser Carbonylverbindungen an der Aromabildung unwahrscheinlich ist.
Graphs of polyhedra; polyhedra as graphs
Relations between graph theory and polyhedra are presented in two contexts. In the first, the symbiotic dependence between 3-connected planar graphs and convex polyhedra is described in detail. In the second, a theory of nonconvex polyhedra is based on a graph-theoretic foundation. This approach eliminates the vagueness and inconsistency that pervade much of the literature dealing with polyhedra more general than the convex ones.