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Poly(ethylene terephthalate) prepared or fabricated by melt processes is shown to contain about 1.5% of extractable, oligomeric material composed mainly of cyclic ethylene terephthalates which exist, at high temperatures, in equilibrium with the molten polymer. An ester interchange‐elimination reaction is proposed as the main route of formation of these compounds. An additional minor component of the polymer, produced by side reactions, is the mixed cyclic bisterephthalate of ethylene and 3‐oxapentamethylene glycols. This compound, together with cyclic bis(3‐oxapentamethylene terephthalate) is also formed in the forced thermal depolymerisation of ethylene/3‐oxapentamethylene terephthalate copolymers.

VERY little seems to be known about the action of peracids on diazohydrocarbons, When a benzene solution containing 9-diazofluorene and perbenzoic acid is warmed, nitrogen is evolved and benzoic acid and fluorenone are formed. On the basis of a positively polarised hydroxyl group in peracids (cf. 11) (

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