4863lonate pathways in H . halobium are identical with those in other organisms.As discussed above, the cryptic stereochemistry involved in the incorporation of glycerol into the membrane lipid of H . halobium was firmly established. In contrast to eubacteria and eukaryotes, it is the sn-C-1 methylene group of 2,3-di-Gphytanyl glycerol that is derived from the sn-C-3 carbon of glycerol and the C-6 carbon of D-glucose. Although stereochemically feasible, a pathway including reduction of ~-glyceraldehyde-3-phosphate can be ruled out, since the present as well as previous studies clearly showed that no hydrogen was lost from either hydroxymethyl group of g l y~e r o l .~,~ Furthermore, the ether-forming reaction is also different from that of 0-alkyl dihydroxyacetone phosphate in mammalian cells?J0 in which a hydrogen of the sn-C-1 methylene group is stereospecifically replaced. Consequently, the most likely mechanism of formation of sn-2,3-0-diphytanyl glycerol in H . halobium apparently includes a unique stereochemical inversion a t the C-2 carbon of glycerol as shown in Scheme I.Acknowledgment. Proton and deuterium N M R spectra were recorded through the courtesy of Dr. M. Uramoto, Institute of Physical and Chemical Research, and Professor H. Set0 and Dr. K. Furihata, the University of Tokyo, to whom we are grateful. (9) Brown, A. The largest [S,M,(SR),]'-molecular aggregate structure reported to date is [E4Mlo(SPh)16]' (E = s, Se; M = Zn, Cd) (l).'

The humic substances in Bayer liquor from a bauxite alumina refinery operating at 145−150 °C have been separated by dialysis into seven fractions of different molecular weight and characterized by acidity, nuclear magnetic resonance (NMR) spectroscopy, infrared spectroscopy, pyrolysis gas chromatography mass spectrometry (py-GC/MS), and thermogravimetric techniques including modulated differential scanning calorimetry. The higher molecular weight fractions contained more aromatic carbon than the lower molecular weight fractions (e.g., >300 000 Da, 56.4%; < 1200 Da, 33.6%). Acidity, NMR, and infrared spectroscopy indicate that carboxylic groups are more prevalent in lower molecular weight fractions (e.g., <1200 Da, 20.1%) than higher molecular weight fractions (e.g., >300 000 Da, 9.8%). Some fractions have particularly interesting structures and properties. For example, lignin-derived humic substances seem to concentrate in the 6000−12 000 Da fraction, as indicated by lignin guaiacyl residues. Involatile polycondensed material concentrates in the molecular weight fraction >300 000 Da. This fraction could be best described as soluble char with unusual properties such as the capacity to hold occluded water above 200 °C.

Supplementary Material Available: Atomic positional and thermal parameters, bond lengths, bond angles, and torsional angles for (Et4N),.lb.(DMF) (1 5 pages). Ordering information is given on any current masthead page. nonmolecular crystal structure of J ~[ I S C~~( S B U~)~~) ( C N )~,~] .~~ (IO) Dance, 1. G.; Garbutt, R. G.; Ma, I.; Scudder, M. L., to be published. Bis[phenyl[ (perfluoroalkanesulfonyl)oxy]iodo]acetylene, PhI+C=SI+Ph.2R&03-, and 1,4-BiNpheny I[ ( perfluoroalkanesulfon yl)ox y ]iodo]-1,3butadiyne, PhI+C=C-C=CI+Ph.2R&03-

No abstract

The adsorption of 13 C-labeled benzene on imogolite has been studied on samples which had been evacuated and then heated to remove water below their decomposition point. After adsorption of labeled benzene, the samples were studied by nuclear magnetic resonance using non-spinning techniques. The results show that benzene can occupy more than one pore type and that water does not displace benzene from the intra-tube pores at atmospheric pressure. A further finding is that there are at least two types of adsorbed benzene in so called inter-tube pores, one of which is more rigidly held than that in intratube pores. The presence of disordered materials at the edge of pores could also play a role in altering the pore mouth thereby creating new types of pores. Moreover, where two tubes do not pack properly, space might be created where an adsorbed molecule may bind more tightly than expected in a conventional pore.