Oligomeric degradation

The crude Bjorkman lignin acidolysis mixture contained both polymeric material and a number of more or less low molecular, chromato-graphically visible products in addition to ketol (XII) and was considered to be a potential source not only of further monomeric but also of dimeric and oligomeric degradation products. The polymeric material was readily removed by filtering the crude mixture of reaction products through a short silica gel column (solvent, dioxane-benzene 1 3). 

Sulfur mustard can be very persistent in soil (Rosenblatt et al., 1995). Persistence depends on the soil type, pH, moisture content, and whether the agent is at the soil surface or buried. Small (1984) reported that when HD was applied to the soil surface, volatilization would be the main route of HD loss (half-life about 30 min), but if the soil was wet, hydrolysis would be the main loss pathway. When sprayed onto soil, a vesicant action was still apparent after about 2 weeks when the agent leaked into the soil, however, a vesicant action was still present after 3 years (DA, 1974). Rosenblatt et al. (1995) state that the persistence of sulfur mustard in soil is due to the formation of oligomeric degradation products that coat the surface of the mustard agent and that are resistant to hydrolysis. 

Other high molecular weight hydrocarbon polymers are not biodegradable, but oligomers of <7j -l,4-isoprene (83), butadiene (84), and styrene (85), are degradable. And there has been further confirmation of biodegradation of oligomeric ethylene (86). 

Bowmer and Bowden75 studied the radiation degradation of poly-2-methyl-l-pentene sulfone and found that at low radiation doses the S02/olefin ratio is 2 1, however at high doses this ratio is decreased and is close to unity. Thus the oligomerization of the olefin, which is the cause for the discrepancy between G(S02) and G(olefin), appears to be reversible. 

The dissertation26 by de Bruijn, Monosaccharides in alkaline medium isomerization, degradation and oligomerization and other publications by... 

The characterization of the end products of the degradation of high-molecular substrates, as well as experiments in which the effect of enzymes on oligomeric substrates was investigated, have contributed significantly to the elucidation of the mode of action of endo-D-galacturonanases. 

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