Synthesis of oligomeric models of coal derived materials for use with GPC calibration. Quarterly report, October-December 1983

The purpose of this study was to develop a set of Gel Permeation Chromatography (GPC) calibration standards for asphaltene and preasphaltene analysis. A series of oligo(aryl ether) and oligo(arylmethylenes) from 170 to 580 g/mole were prepared via modified Ullmann-type reactions (ethers) and condensation of an aryl lithium derivative with an aryl carboxaldehyde, followed by reduction of the resulting carbonol (methylenes). These compounds were examined as molecular weight calibration standards for GPC analysis. A nearly linear plot was found to exist between the logarithm of molecular weight times mol fraction hydrogen versus retention volume with THF as the solvent. Further this plot was coincident with commercial polystyrene standards (600 to 2000 g/mol) and with the majority of our lignite derived asphaltenes and preasphaltenes. Work in our laboratory suggests that universal calibration plots for GPC analysis of lignite-derived preasphaltene and asphaltene liquefaction products are possible for determining number and weighted average molecular weight values. Universal calibration plots based on the logarithm of the hydrodynamic volume, number average molecular weight times hydrogen content, result in a smooth curve coincident with polystyrene standards, model compounds, and lignite derived asphaltenes/preasphaltenes. The data which supports the above hypothesis is presently limited and has only been measured for lignite-derived materials. 18 references, 6 figures

Unstable B-chromosomes in Ranunculus bulbosus

A B-chromosome system has been found in Ranunculus bulbosus. 87 plants from Monte Croce della Serra in Umbria (Italy) have been examined and 12 of these have shown Bs. Bs in R. bulbosus are unstable (in roots, leaves and male meiocytes), very small (less than 1 mu m), can reach relatively high numbers (up to 19B) and are heterochromatic (visible in interphase nuclei after Feulgen or Giemsa staining procedures). In spite of the wide intra tissue range of B number the mitotic behaviour of B is very often regular. Also microsporogenesis observations have shown that Bs can pair and segregate regularly in the A chromosome fashion, especially when the B-number in meiocytes is low. Irregularities (clumps, laggards, micronuclei) ate much more frequent when Bs are more than six