426. Alkylperoxy-radicals. Part III. Kinetics of autoxidations retarded by aromatic amines

Abstract

A lkylfieroxy-radicals. Part I I I . 2217 426. Alkylperoxy-radicals. Part III? Kinetics of Autoxidations Retarded by A r m t i c Arnines.

Inhibition of the Autoxidation of Organic Substances in the Liquid Phase.

“…ROOH + R'SR" -> ROH + R'S(0)R" (34) ROOH + R'S(0)R" -> ROH + R'S(0)2R" (35) Monosulfides which contain at least one aliphatic or cycloaliphatic group attached to the sulfur atom are more effective antioxidants than mercaptans and disulfides, while diaryl sulfides and sulfones are inactive (87). The most active sulfides contain one ferf-butyl group attached to the sulfur and a second group which should be isopropyl, ferf-butyl, -CH (CHS) CH=CHR, or -CH2CH2COR (12a).…”

“…By analogy, the amine-hydroperoxide reaction probably also involves an initial polar reaction, the products of which rearrange to give either stable products (reaction 9) or free radicals (reaction 8). Thus, N,Ndimethylaniline is sometimes a weak catalyst (35,169) and sometimes a weak inhibitor of hydrocarbon autoxidations (142); this suggests that this amine can give either free radicals or stable products on reaction with hydroperoxides, just as it can on reaction with benzoyl peroxide (323). Aromatic primary and secondary amines that are inhibitors of free radicals, on the other hand, appear to decompose hydroperoxides without the production of free radicals (167) (see Section IV).…”

“…In view of the fact that some free radicals must be involved in the reaction it is surprising that alkylamines only rarely have a catalytic effect on an autoxidation (35). On the contrary, most examples recorded in the literature indicate that these amines are either inactive (107) or are weak inhibitors (4,169).…”

“…It seems probable that their inhibiting activity is due to the fact that peroxide-decomposition reactions which do not lead to the production of radicals (e.g., reaction 52) outweigh the catalytic effect of those decomposition reactions which do lead to free radicals. The ready transfer of the «-hydrogen atoms to free radicals may also contribute to their inhibiting power, but it can also lead to a chain-transfer process in which the new chain-carrying species promotes an increased rate of oxidation (35).…”

Discoloration in Fire-Retardant Flexible Polyurethane Foams

“…If isocyanate is not available, oxygen will promptly react with aromatic amines. This is especially true when secondary amines are formed, which react slower with -NCO and faster with oxygen in comparison to primary amines [18,19].…”