Zinc diisopropyl dithiophosphate

ROa- + A - R02A+ Manganous stearate Zinc diisopropyl dithiophosphate... 

R02 + AH -> ROOH + A- Phenol 4-MeO-phenol 2.6- tert-Bu2-4-methylphenol 2.4.6- ferf-Bu3-phenol (VIH) N-Methylaniline Diphenylamine (MeO) 2-diphenylamine (IV) (MeO) 2-diphenylhydroxylamine (V) Zinc diisopropyl dithiophosphate... 

The kinetics of the zinc diisopropyl dithiophosphate-in-hibited oxidation of cumene at 60°C. and Tetralin at 70°C. have been investigated. The results cannot be accounted for solely in terms of chain-breaking inhibition by a simple electrow-transfer mechanism. No complete explanation of the Tetralin kinetics has been found, but the cumene kinetics can be explained in terms of additional reactions involving radical-initiated oxidation of the zinc salt and a chain-transfer step. Proposed mechanisms by which zinc dialkyl dithiophosphates act as peroxide-decomposing antioxidants are discussed. 

More recently it has been shown (6, 7) that zinc dialkyl dithiophosphates also act as chain-breaking inhibitors. Colclough and Cunneen (7) reported that zinc isopropyl xanthate, zinc dibutyl dithiocarbamate, and zinc diisopropyl dithiophosphate all substantially lowered the rate of azobisisobutyronitrile-initiated oxidation of squalene at 60°C. Under these conditions, hydroperoxide chain initiation is negligible, and it was therefore concluded that inhibition resulted from removal of chain-propagating peroxy radicals. Also, consideration of the structure of these zinc dithioates led to the conclusion that no suitably activated hydrogen atom was available, and it was suggested that inhibition could be accounted for by an electron-transfer process as follows ... 

The importance of ionization of the metal-sulfur bond in the electron-transfer process accounts for inhibitory properties being observed only for compounds of types I and II. Support for this mechanism was also obtained by the isolation of the disulfide (IV) from a reaction between peroxy radicals and zinc diisopropyl dithiophosphate. 

The present paper reports the results of a kinetic study of the inhibition of the azobisisobutyronitrile-initiated autoxidation of cumene at 60 °C. and of Tetralin at 70 °C. by zinc diisopropyl dithiophosphate, undertaken to test the validity of the chain-breaking inhibition mechanism proposed above. In addition, the effectiveness of several metal dialkyl dithiophosphates as antioxidants in the autoxidation of squalane... 

The results of a study of the zinc diisopropyl dithiophosphate-inhib-ited oxidation of cumene at 60°C. are shown in Figures 1 to 3. The initial oxidation rate is directly proportional to the AIBN concentration, but the dependence of initial rate on the cumene concentration or the reciprocal of the zinc salt concentration, although reasonably linear, is not in direct proportion. 

From these results, it is clear that neither Equation A nor B represents the kinetics of the zinc diisopropyl dithiophosphate-inhibited autoxi-dation of cumene or Tetralin. This does not immediately indicate that the mechanism in Scheme 1 is wrong since it is highly idealized and takes no account of possible side reactions. A similar situation occurs in the inhibition of hydrocarbon autoxidation by phenols (AH), for which a basic mechanism similar to that in Scheme 1 is accepted. Termination occurs via Reactions 7 and 8 instead of Reactions 5 and 6. 

C Zinc diisopropyl dithiophosphate, 0.0013M, plus cumene hydroperoxide, 0.017M... 

One approach to obtaining structural information on surface films is reflectance-absorbance infra-red (RAIR) spectroscopy and Fourier Transform IR (Foster, 1999). Model materials were prepared by thermal and thermooxidative decomposition of zinc diisopropyl-dithiophosphate. Lubricant-derived... 

B Potassium di(4-methyl-2-pentyl)dithiophosphate, 0.005M C, D, E, F, G 0.001 M lead, ferric, nickel, zinc, and cadmium diisopropyl dithiophosphates, respectively... 

Sodium diisobutyl dithiophosphate Sodium diisopropyl dithiophosphate Sodium di-(methylamyl) dithiophosphate Stearyl hydroxyethyl imidazoline flotation collector, zinc sulfide ore Sodium di-s-butyl dithiophosphate flotation depressant Acacia Calcium ferrocyanide Carboxymethylcellulose sodium Hydrofluoric acid Potassium ferricyanide Potassium ferrocyanide Sodium metabisulfite flotation depressant, copper ores Dicyandiamide Guanidine nitrate 2-Mercaptoethanol Phosphorus pentasulfide Quinolinic acid... 

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