Oxidation

Polypropylene samples, in which the three different carbon atoms along the chain were selectively labeled with carbon-13, were subjected to radiation under waterlogged and air atmospheres, and to post-irradiation exposure in air at miscellaneous temperatures. By using solid-state 13C NMR measurements at way temperature, we have been able to identify and quantify the oxidation products. The isotopic labeling provides insight into chemical reaction mechanisms, since oxidation products can be traced back to their positions of origin on the macromolecule. The major products include peroxides and alcohols, some(prenominal) formed at tertiary carbon sites along the chain. separate products include methyl group ketones, acids, esters, peresters, and hemiketals formed from reaction at the tertiary carbon, to discoverher with in-chain ketones and esters from reaction at the secondary chain carbon. No evidence is found of products arising from reactions at the methyl side chain. earthshaking temperature-dependent differences are apparent; for example much higher yields of chain-end methyl ketones, which are the indicator product of chain scission, are generated for both elevated temperature irradiation and for post-irradiation treatment at elevated temperatures.



Time-dependent plots of yields of the confused oxidation products have been obtained under a wide mountain chain of conditions, including the post-irradiation oxidation of a sample at room temperature in air that has been monitored for 2 years. Radiation-oxidation products of polypropene are contrasted to products measured for 13C-labeled polythene in an earlier investigation: the peroxides formed in irradiated polypropylene are remarkably longer lived, the non-peroxidic products are significantly different, and the boilers suit ratios of oxidation products in polypropylene change relatively petite as a function of the extent of oxidation.If you want to get a full essay, order it on our website: Orderessay



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