Photodegradation pattern

Photolysis of Model Compound II. Compound II, the bis-2-hydroxy propyl ether of bisphenol A, represents a section of a BAE polymer. Figure 4 shows the GC peaks as drawn by the computer and Table II shows the significant peaks that appeared in the GC/MS spectrum and their corresponding m/e ratios. The proposed photodegradation pattern is shown in Scheme 2. 

The largest photoproduct fraction formed (X) had a retention time of around 815 seconds. In comparison to other photoproducts from either I or III, the retention time of this product is short and the quantity formed is large. The MS spectra showed the molecular ion peak at 244. From Scheme 2, it can be seen in the case of photoproduct X (m/e=244), if cleavage occurs at the isopropyl-idene group, a biphenyl is generated. As stated earlier when studying the photodegradation pattern of model com-... 

Juvet et al found that with low concentrations of additives, the photodegradation pattern of a polymer is not affected and new products appear from photolysis of the additives. As an example Table 7.56 lists the retention indices on SE-30 for the additional photolysis products from two similar sample, 1.0% dilaurylthiodipropionate in polyethylene and 1.0% distearylthiodipropionate in polyethylene. No difficulty is found in differentiating between these two additives by photolysis gas chromatography although they are of closely related structure indeed the similarity in structure is readily apparent from the constant difference of 600 I units in the homologous peaks of these two additives. The product from dilaurylthiodipropionate eluting at I = 1690 was identified... 

However, predicted concentrations do not always accurately reflect those measured this is due to several reasons, including variation in consumption patterns throughout the year, the use of an inaccurate excretion rate /excreted UV exposure setting off unavoidable photodegradation processes during sampling and transportation, inappropriate sample conservation methods and adsorption onto particulates present in wastewater [34, 49],... 

A number of other, but minor primary photoproducts was also found, among them the products expected from a radical (photo-Claisen) rearrangement and from photohydrolysis of the ortho chlorine 2- and 4-chlorophenol were detected too, but their formation remained unexplained. The photodegradation quantum yield of dichlorprop did not depend on pH and was 50 times smaller than that of the anionic form of the related monohalo-genated compound mecoprop (see above) [77]. This is another example of the marked influence of the pattern of ring halogen substitution on the course and on the efficiency of photodegradation. 

In the second paper. Part II of the previously cited series, Lachman et al. (37) discussed many of the problems encountered when dealing with solid materials, particularly the fact that the photodegradation of solids was a surface phenomenon. They noted that different rates of fading were found, ranging from 1.5 to 240 and they could observe no particular pattern related tothe phenomena. 

Degradation pattern 1. Biodegradation 2. Photodegradation Aerobic biodegradation... 

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