Antioxidants and stabilizers, CXIII. Oxidation products of the antidegradant ethoxyquin

Taimr, L.; Prusíková, M.; Pospı́šil, J.

doi:10.1002/apmc.1991.051900104

Cited by 23 publications

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“…During the photolysis of compounds A with R 2 = H in organic solvents (benzene, toluene, alkanes, propanol-2), the hydrogen atom breaks off from the molecule of dihydroquinoline, and an aminyl radical forms, which decays at the ambient temperatures predominantly in recombination reaction [5] giving 1-8 dimer B [6,7] (Shceme 1).…”

Section: Resultsmentioning

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Phototransformations of non‐toxic antioxidants, the derivatives of 1,2‐dihydroquinolines, in homogeneous and micellar solutions

Nekipelova

1999

International Journal of Photoenergy

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Abstract. Reactions of transient species photogenerated from 6-R-2,2,4-trimethyl-1,2-dihydroquinolines (TMDQ) are very sensitive to medium variation. In anhydrous organic solvents, aminyl radicals were generated. They decay in the reaction of dimerization with the second-order rate constant decreasing in a row heptane>benzene>2-propanol. When passing from organic solvents to water, methanol, and water-alcohol solutions, the kinetics and the direction of the reaction crucially change. As a result of the photolysis, the product of the addition of a solvent to the double bond of heterocycle, 4-hydroxy-or 4-methoxy-6-R-2,2,4-tetramethyl-1,2,3,4-tetrahydroquinoline is formed in water and methanol, respectively. The transformation is a complex reaction, and the formation of excited transient species is followed by a sequence of first-order and pseudo-first-order reactions. Unlike the photolysis in anhydrous organic solvents, the reaction in water and methanol does not involve aminyl radicals. In aqueous solutions, the first-order rate constants for the decay of transient species are higher in acidic and neutral solutions. At the pH close to pK a of the transient species, it drops, indicating that the neutral form is less reactive. The same product is formed over the whole range of pH. For the anionic surfactant (SDS) in acidic and alkaline solutions, the apparent rate constant in the micellar solutions is lower than that in the aqueous (negative micellar catalysis). At the medium pH, a positive micellar catalysis is observed, and the rate constant of the decay depends linearly on the concentration of TMDQ in the micelles, indicative of the direct reaction between TMDQ and the cationic transient species.

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Section: Resultsmentioning

confidence: 99%

Phototransformations of non‐toxic antioxidants, the derivatives of 1,2‐dihydroquinolines, in homogeneous and micellar solutions

Nekipelova

1999

International Journal of Photoenergy

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“…The analogous quinoimines are formed in the PNA series. In the DHQ series, quinoimines 13 and 14 are formed from the aminyl; quinoimine 15 arises from the C-N coupling product of 14 (17). Quinoimines are also formed from substituted phenothiazines.…”

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“…Most products are colored (3,12,17). N-Phenyl-l,4-benzoquino-4-imine (10) is formed from unsubstituted DPA.…”

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Activity Mechanisms of Amines in Polymer Stabilization

Pospı́šil

1996

Advances in Chemistry

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Aromatic and heterocyclic amines have a crucial importance for stabilization of rubbers, plastics, and coatings. A detailed examination of their chemistry revealed processes accounting for antioxidant, antifatigue, and photostabilizing activities. Aspects of chemical transformations, characteristic for the generation of radical intermediates, and products from amines under conditions of polymer degradation were exploited to explain the scavenging activities of R· and ROO· as the key stabilization pathway. The data are interpreted in a way that is applicable to developing new ideas and systems for effective polymer stabilization. TTRENDS IN THE STABILIZATION OF CONVENTIONAL POLYMERS in the 1990shave responded to several problems: prevention of degradation caused by residues of polymerization catalysts of new generations remaining in the pol ymer bulk; expansion of technologies exploiting more drastic processing con ditions; broader use of macromolecular systems filled with inorganics; use of polymer products in environments with increased chemical and physical ag gressiveness in the household, machinery, energetics, automotive, or agricul tural industries; and application of recycled polymer waste. Research and development has been aimed at innovative technologies for processing and long-term stabilization of plastics, rubbers, and coatings. Data obtained in studies of influences of structural factors governing the "inherent chemical efficiency" of stabilizers have been reinterpreted by using up-to-date knowl edge (1-3).An elucidation of physical factors governing stabilizer efficiency (4) ac counts for a new insight into the necessary conditions for efficient polymer stabilization. Adjusting the molecular architecture of stabilizers to maximize

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The reaction of 1‐cyano‐1‐methylethyl radical with antidegradant ethoxyquin and its aminyl and nitroxide derivatives

Taimr

Šmelhausová

Prusíková

1993

Angew. Makromol. Chem.

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6-Ethoxy-2,2,4-trimethyl-l,2-dihydroquinoline (ethoxyquin, I) does not react with the model alkyl radical, 1-cyano-1-methylethyl, in an inert atmosphere. On the other hand, its aminyl derivative (II) reacts readily with the model alkyl radical; the main product of this reaction is 6-ethoxy-8-(1 -cyano-1 -methylethyl)-2,2,4-trimethyl-l,2-dihydroquinoline (V), while 6-ethoxy-1-( l-cyano-l-methylethyl)-2,2,4-trimethyl-l,2-dihydroquinoline (VI) is formed as a by-product. 6-Ethoxy-2,2,4-trimethyl-1 ,Zdihydroquinoline-N-oxyl (111) also effectively deactivates the model alkyl radical to form 6-ethoxy-8-( 1 -cyano-1 -methylethoxy)-2,2,4-trimethyl-l,2-dihydroquinoline (X).It follows from these results that I is an ineffective antidegradant in oxygen-free atmosphere. However, at very low oxygen concentrations, I becomes capable of deactivating alkyl radicals. Together with its ability to deactivate alkylperoxide radicals, this explains the high antifatigue activity of I.In the presence of silica gel, V is readily cyclized to 8-ethoxy-l,2,3,4-tetrahydro-2imino-l,1,4,4,6-pentamethylpyrrolo[3,2,l-ij]quinoline (VIII). VI undergoes thermal decomposition into its components, i. e., aminyl I1 and the model radical. Photodecomposition of X on silica gel yields 6-ethoxy-2,2,4-trimethyl-8-quinolone (XIII). ZUSAMMENFASSUNG 6-Ethoxy-2,2,4-trimethyl-1,2-dihydrochinolin (Ethoxyquin, I) reagiert nicht mit dem Modell-Alkylradikal 1 -Cyan-1 -methylethyl in inerter Atmosphare. Sein Aminylderivat (11) reagiert dagegen leicht mit dem Modellalkyl; dabei wurden 6-Ethoxy-8-( 1 -cyan-1methylethyl)-2,2,4-trimethyl-1,2-dihydrochinolin (V) als Hauptprodukt und 6-Ethoxy-1-(1 -cyan-1 -methylethyl)-2,2,4-trimethyl-l,2-dihydrochinolin (VI) als Nebenprodukt erhalten. Auch 6-Ethoxy-2,2,4-trimethyl-1,2-dihydrochinolin-N-oxyl(III) desaktiviert wirksam die Modellradikale unter Bildung von 6-Ethoxy-8-(1 -cyan-1 -methyl-ethoxy)-2,2,4-trimethyl-1,2-dihydrochinolin (X). CCC OOO3-3146/93/$05.00 199 L. Taimr, M. Smelhausova, M. PrusikovaIn Abwesenheit von Sauerstoff ist I als Antidegradant ganz unwirksam. Jedoch schon eine sehr niedrige Konzentration von Sauerstoff befahigt I, Alkylradikale zu desaktivieren. Seine hohe alterungsschutzende Aktivitat ist also durch die Fahigkeit erklart, sowohl Alkyl-als auch Alkylperoxyradikale zu desaktivieren.V cyclisiert leicht auf Kieselgel unter Bildung von 8-Ethoxy-l,2,3,4-tetrahydro-2-imino- I ,1,4,4,6-pentamethylpyrrolo[3,2,1-ij]-chinolin (VIII). VI spaltet sich bei hoherer Temperatur in seine Komponenten -Aminyl I1 und das Modellradikal. X spaltet sich unter Lichtwirkung auf Kieselgel unter Entstehung von 6-Ethoxy-2,2,4-trimethyl-8chinolon (XIII).

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Antioxidants and stabilizers, CXIII. Oxidation products of the antidegradant ethoxyquin

Cited by 23 publications

References 8 publications

Phototransformations of non‐toxic antioxidants, the derivatives of 1,2‐dihydroquinolines, in homogeneous and micellar solutions

Phototransformations of non‐toxic antioxidants, the derivatives of 1,2‐dihydroquinolines, in homogeneous and micellar solutions

Activity Mechanisms of Amines in Polymer Stabilization

The reaction of 1‐cyano‐1‐methylethyl radical with antidegradant ethoxyquin and its aminyl and nitroxide derivatives

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