Nonspectroscopic Physical Methods

In the case of relatively stable and crystalline 1,2-dioxetanes, which can be isolated by crystallization and elution chromatography on silica gel,36-40 the melting points (Tables I and II) have served as good criteria of purity. However, in some cases, e.g., derivatives (lu), (lx), (lab), (lac), (laf) and (lab), decomposition points are involved, which limits this criterion for purity and structure confirmation. Where liquid diox-etanes are obtained, purification other than column chromatography is not feasible because of the thermal lability of these materials. 

45 (a) A. A. Frimer and P. D. Bartlett, Abstr. IUPAC Congr. 25ih, I975-, (b) A. A. 

These classical characterization methods have been used even for 1,2-dioxetanes, which cannot be obtained as pure, crystalline solids, for example (lw).J6b 

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