ISSN:
0887-624X
Keywords:
acrylic acid
;
phenothiazine
;
p-methoxyphenol
;
inhibition, mechanism of
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Inhibition of acrylic acid by p-methoxyphenol fits a conventional stoichiometric mechanism but phenothiazine inhibits acrylic acid via a completely different, catalytic cycle which does not depend on the presence of oxygen. We propose that this mechanism may involve a pair of single electron transfer reactions between free radicals, phenothiazine N-radicalcation, and phenothiazine itself, the latter being cyclically regenerated. Arrhenius equations were derived for the rates of disappearance of inhibitor and oxygen in acrylic acid stabilized with phenothiazine and with p-methoxyphenol and also with phenothiazine in the absence of oxygen. The practical implication of high oxygen to p-methoxyphenol consumption ratios is quite important: if commercial acrylic acid (usually stabilized with p-methoxyphenol) is inadvertently heated during storage, the limiting substance determining the onset of polymerization will be the dissolved oxygen and not p-methoxyphenol unless oxygen (air) is being supplied to and dissolved in the liquid at a rate sufficient to overcome the rate of its consumption.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pola.1992.080300407
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