Ozonolysis of Polyisoprene Popcorn Polymer

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Abstract
Ozonolysis of polyisoprene popcorn polymer gave the volatile products: water, formic acid, acetic acid, levulinaldehyde, 2,5-hexanedione, and propionic acid. The rates of formation of levulinaldehyde and 2,5-hexanedione varied during the 96-hour ozonolysis period; more levulinaldehyde was formed during the early stages, and more 2,5-hexanedione during the later stages. The molar yields of formic and acetic acid were approximately 20 and 10 times larger, respectively, than the average hexanedione or levulinaldehyde yield. A chain unzipping mechanism is postulated for the production of most of the formic and acetic acids, and it is believed that most of the 2,5-hexanedione is formed in secondary reactions initiated by alkoxy or peroxy radicals. A large amount of oxygen remained on the polymer which still had a high degree of unsaturation following the ozonolysis. Ozonolysis of bulk PIP is not a satisfactory way for the determination of head-to-head and tail-to-tail structural sequences. The evidence obtained, however, indicates that the polymer is composed primarily of head-to-tail structural units.

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