Mechanisms of Ozonation of N-(1,3-Dimethylbutyl)-N′-Phenyl-p-Phenylenediamine

1983 ◽  
Vol 56 (2) ◽  
pp. 431-439 ◽  
Author(s):  
R. P. Lattimer ◽  
E. R. Hooser ◽  
R. W. Layer ◽  
C. K. Rhee
Keyword(s):  
Amine Oxide ◽  
Film Theory ◽  
Nitroxide Radical ◽  
Side Chain ◽  
Low Molecular Weight ◽  
Protective Film ◽  
Oxide Formation ◽  
Chain Oxidation ◽  
Rubber Compounds ◽  
Ozonation Product

Abstract The ozonation products of a common rubber antiozonant, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (HPPD), have been separated by liquid chromatography and identified by mass spectrometry. Three principal mechanisms appear to govern the ozonation of HPPD. Amine oxide formation leads to observed nitrosoaryl and nitroaryl products. Side-chain oxidation leads to several low molecular weight products, including some that contain an amide moiety. Nitroxide radical formation leads to a nitrone that is the most abundant ozonation product; a dinitrone is also formed. Ozonation of HPPD occurs mainly with degradation of the alkyl portion of the molecule. The results of this study are consistent with a combined “scavenger-protective film” theory of antiozonant protection of rubber compounds.

Ozonation of amines. II. Competition between amine oxide formation and side-chain oxidation

1968 ◽  
Vol 33 (7) ◽  
pp. 2675-2680 ◽  
Author(s):  
Philip S. Bailey ◽  
David A. Michard ◽  
Abdul-Ilah Y. Kashhab
Keyword(s):  
Amine Oxide ◽  
Side Chain ◽  
Oxide Formation ◽  
Chain Oxidation

The Ozonation of N,N′-Di-n-Octyl-p-Phenylenediamine and N,N′-Di-(1,1-Dimethylethyl)-p-Phenylenediamine

1991 ◽  
Vol 64 (5) ◽  
pp. 780-789 ◽  
Author(s):  
R. P. Lattimer ◽  
R. W. Layer ◽  
E. R. Hooser ◽  
C. K. Rhee
Keyword(s):  
Film Theory ◽  
Chain Scission ◽  
Protective Film ◽  
Self Healing ◽  
Reaction Products ◽  
Double Bonds ◽  
Final Theory ◽  
Rubber Compounds ◽  
Rubber Surface ◽  
Paraffin Waxes

Abstract Ozone attack on rubber compounds causes characteristic cracking perpendicular to the direction of applied stress. This degradation is caused by reaction of ozone with the double bonds in the rubber molecules. This causes chain scission and the formation of various decomposition products. The general subject of protection of rubber against ozone attack has been reviewed by a number of authors. In order to control the effects of rubber ozonation, either paraffin waxes or chemical antiozonants are added to unsaturated rubbers. The most effective antiozonants are N,N′-disubstituted-p-phenylenediamines (PPDAs), in which at least one of the side groups is alkyl (preferably sec-alkyl). Several theories have appeared in the literature regarding the mechanism of antiozonant protection. The “scavenger” model states that the antiozonant blooms to the surface and preferentially reacts with ozone so that the rubber is not attacked until the antiozonant is exhausted. The “protective film” theory is similar, except that the ozone-antiozonant reaction products form a film on the rubber surface that prevents (physically and perhaps chemically as well) ozone attack on the rubber. A third “relinking” theory states that the antiozonant prevents scission of the ozonized rubber or else recombines severed double bonds. A final theory states that the antiozonant reacts with the ozonized rubber or Criegee zwitterion (carbonyl oxide) to give a low-molecular-weight, inert, “self-healing” film on the rubber surface. Currently, the most accepted mechanism of antiozonant action is a combination of the scavenger and protective film theories.

Mechanisms of Ozonation of N,N′-di-(1-Methylheptyl)-p-Phenylenediamine

1980 ◽  
Vol 53 (5) ◽  
pp. 1170-1190 ◽  
Author(s):  
R. P. Lattimer ◽  
E. R. Hooser ◽  
H. E. Diem ◽  
R. W. Layer ◽  
C. K. Rhee
Keyword(s):  
Molecular Weight ◽  
Mass Spectroscopy ◽  
Surface Film ◽  
Nitroxide Radical ◽  
Low Molecular Weight ◽  
Protective Film ◽  
Radical Intermediate ◽  
Molecular Weights ◽  
Mechanistic Pathway ◽  
Electron Impact Mass

Abstract The ozonation products of a common rubber antiozonant, N,N′-di-(l-methylheptyl)-p-phenylenediamine (DOPPD), have been separated by liquid or gas chromatography. Molecular weights of about thirty LC separated components have been measured by field desorption mass spectroscopy. Elemental formulae have been determined by atomic composition mass spectroscopy. Other structural details have been elucidated by electron impact mass spectroscopy and attenuated total reflectance infrared spectroscopy. Two principal mechanisms appear to govern the ozonation of DOPPD. Amine oxide formation leads to observed nitrosoaryl and nitroaryl products. The second major mechanistic pathway is side chain oxidation. This leads to a number of low molecular weight components, including some that contain an amide moiety. A third (minor) mechanistic pathway involves a nitroxide radical intermediate and leads to the formation of a stable dinitrone species. The surface film formed on ozonation of a black loaded natural rubber sheet containing DOPPD has also been examined. The film contains appreciable quantities of unreacted DOPPD and many of the same low molecular weight components as observed in the ozonized liquid antiozonant. It is clear that DOPPD blooms to the rubber surface and acts as a scavenger for ozone. The results are consistent with a combined “scavenger-protective film” mechanism for antiozonant protection.

scholarly journals Stereochemistry of the side chain oxidation of 5 beta-cholestane-3 alpha,7 alpha,12 alpha-triol in man.

1980 ◽  
Vol 255 (4) ◽  
pp. 1483-1485
Author(s):  
R.F. Hanson ◽  
P. Szczepanik-Van Leeuwen ◽  
G.C. Williams
Keyword(s):  
Side Chain ◽  
Chain Oxidation ◽  
Alpha 7

scholarly journals The metabolism of cholesterol in the presence of liver mitochondria from normal and thyroxine-treated rats

1965 ◽  
Vol 94 (3) ◽  
pp. 594-603 ◽  
Author(s):  
KA Mitropoulos ◽  
NB Myant
Keyword(s):  
Carbon Dioxide ◽  
Steam Distillation ◽  
Liver Mitochondria ◽  
Incubation Mixture ◽  
Side Chain ◽  
Volatile Fraction ◽  
Low Molecular Weight ◽  
Butanol Extract ◽  
Rate Limiting ◽  
Layer Chromatography

1. [26-(14)C]- and [4-(14)C]-Cholesterol were incubated with liver mitochondria from normal and thyroxine-treated rats, and the radioactivity was measured in the carbon dioxide evolved during the incubation, in a butanol extract of the incubation mixture and in a volatile fraction containing substances of low molecular weight derived from the side chain of cholesterol. The butanol extract was separated by paper chromatography into three radioactive fractions, one of which contained the steroids more polar than cholesterol. 2. The butanol extract from incubations with [4-(14)C]cholesterol contained a radioactive substance moving with the same R(F) as cholic acid on thin-layer chromatography. 3. After incubation with [26-(14)C]-cholesterol, 60-80% of the radioactivity extracted by steam-distillation of the incubation mixture at acid pH was recovered as [(14)C]propionic acid. 4. In the presence of [26-(14)C]cholesterol, mitochondria from thyroxine-treated rats produced more radioactivity in carbon dioxide and in the volatile fraction, and less radioactivity in the fraction containing the polar steroids, than did mitochondria from normal rats. In the presence of [4-(14)C]cholesterol, mitochondria from thyroxine-treated rats produced the same amount of radioactivity in the polar steroids as did normal mitochondria. 5. Thyroxine treatment had no effect on the capacity of the mitochondria to oxidize propionate to carbon dioxide. 6. These results are best explained by supposing that thyroxine stimulates a rate-limiting reaction leading to the cleavage of the side chain of cholesterol, but has little or no influence on the hydroxylations of the ring system or on the oxidation of the C(3) fragment removed from the side chain.

Characterization of the cytochrome P450 involved in side-chain oxidation of cyclophosphamide in humans

1996 ◽  
Vol 51 (3-4) ◽  
pp. 297-301 ◽  
Author(s):  
F. Bohnenstengel ◽  
U. Hofmann ◽  
M. Eichelbaum ◽  
H. K. Kroemer
Keyword(s):  
Cytochrome P450 ◽  
Side Chain ◽  
Chain Oxidation
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