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.
THIN-LAYER CHROMATOGRAPHY OF ALIPHATIC 2,4-DINITROPHENYLHYDRAZONES.
Abstract Thin-layer chromatographic procedures are described for the separation of 2,4-dinitrophenylhydrazones into: 1. Individual members of homologous series by a partition system between 2-phenoxyethanol supported on kieselguhr G and light petroleum (b.p. 100–120°), 2. n-Aldehyde, n-alkan-2-one and n-alk- i -en-3-one derivatives on aluminium oxide G with 4% diethyl ether in light petroleum (b.p. 30–40°) as the solvent, 3. n-Alkanal, n-alk-2-enal, n-alka-2,4-dienal, n-nona-trans-2,trans-6-dienal and n-nona-trans-2,cis-6-dienal derivatives on plates of aluminium oxide G containing 25% AgNO3 (w/w) with 16% diethyl ether in light petroleum (b.p. 30–40°) as the developing solvent. These procedures have been combined in two-dimensional techniques to give a separation of mixtures of the 2,4-dinitrophenylhydrazones of the normal homologous series of alkan-2-ones, alk- i -en-3-ones, alkanals, alk-2-enals, alka-2,4-dienals, and alka-2,6-dienals.
Effects of Equipment Dimensions on Liquid Mixing Time of Bubble Column with Draft Tube
The liquid mixing time of a bubble column with a draft tube is experimentally studied. The diameter and height of the column, the diameter and length of the draft tube, and the mode of sparging gas were changed and the liquid mixing time was measured.The lengths of bottom and top clearances have significant effects on the liquid mixing time. The liquid mixing time increases with increasing column aspect ratio of height to diameter. The liquid mixing time of the bubble column with a draft tube is longer than that of a standard bubble column when the column aspect ratio is relatively high. The liquid mixing time has a minimum when the diameter ratio of draft tube to column is 0.5 to 0.6. These effects of equipment dimensions are expressed by an equation. In the experiment using different solutions, the liquid mixing time becomes shorter with increasing liquid surface tension, or with increasing liquid viscosity.