Metal complexes as antioxidants. V. Inhibition of hydrocarbon autoxidation by cupric complexes of dialkyldithiophosphoric and dialkyldithiocarbamic acids

1978 ◽  
Vol 56 (2) ◽  
pp. 157-163 ◽  
Author(s):  
J. H. B. Chenier ◽  
J. A. Howard ◽  
J. C. Tait
Keyword(s):  
Liquid Phase ◽  
Initial Rate ◽  
Copper Ions ◽  
Radical Scavenging ◽  
Peroxy Radical ◽  
Oxygen Absorption ◽  
Inhibition Rate ◽  
Chain Initiation ◽  
Considerable Length ◽  
Alkylperoxy Radicals

Liquid-phase reactions of alkylperoxy radicals with cupric complexes of dialkyldithiophosphoric and dialkyldithiocarbamic acids have been examined. These complexes have been shown to be extremely efficient peroxy radical scavenging antioxidants for hydrocarbon autoxidation. Initial rates of oxygen absorption by typical hydrocarbons were extremely slow implying inhibition rate constants > 106 M−1 s−1. The initial rate of disappearance of the dithiocarbamate was equal to the rate of chain initiation (Ri) whereas the rate of disappearance of the dithiophosphate was twice as fast as Ri. In both cases the rate of complex disappearance slowed down as the complex was consumed. Autoxidation of styrene commenced as soon as the complex disappeared while cumene did not absorb oxygen for a considerable length of time after complex destruction. Cumylperoxy radicals were converted to α-cumyl alcohol, α-methylstyrene, and acetophenone by reaction with these complexes and the copper ions were eventually precipitated as copper sulphate. In the case of the dithiocarbamate three intermediate cupric complexes were detectee by epr spectroscopy.

LIQUID-PHASE OXIDATION OF CYCLOHEXENE IN THE PRESENCE OF BENZALDEHYDE

1966 ◽  
Vol 44 (15) ◽  
pp. 1817-1825 ◽  
Author(s):  
Tsuneo Ikawa ◽  
Toshiyuki Fukushima ◽  
Minoru Muto ◽  
Tadahisa Yanagihara
Keyword(s):  
Double Bond ◽  
Liquid Phase ◽  
Room Temperature ◽  
Peroxy Radical ◽  
Liquid Phase Oxidation ◽  
Oxygen Absorption ◽  
Peroxy Radicals ◽  
Phase Oxidation ◽  
Epoxidation Of Cyclohexene

The kinetics, at room temperature, of the oxidation of cyclohexene in the presence of benzaldehyde have been measured, and the nature of the products when this oxidation was performed at 70 and 110 °C has been studied. The results indicate that the attack of benzoyl peroxy radical on the double bond of cyclohexene retards the rate of oxygen absorption and also causes epoxidation of cyclohexene. The epoxidation of cyclohexene by peroxybenzoic acid (produced from aldehyde) seems to proceed simultaneously with the epoxidation by peroxy radicals during the oxidation of cyclohexene in the presence of benzaldehyde.

Metal complexes as antioxidants. 7. Kinetics of inhibition of styrene autoxidation by zinc di-isopropyldithiophosphate

1980 ◽  
Vol 58 (1) ◽  
pp. 92-95 ◽  
Author(s):  
J. A. Howard ◽  
S-B. Tong
Keyword(s):  
Chain Transfer ◽  
Peroxy Radical ◽  
Chain Termination ◽  
Oxygen Absorption ◽  
Reaction Products ◽  
Radical Chain ◽  
Chain Initiation ◽  
Styrene Concentration ◽  
Kinetics Of ◽  
Kinetics Of Inhibition

Rates of oxygen absorption by styrene (RH) containing 2,2,3,3-tetraphenylbutane and zinc di-isopropyldithiophosphate at 30 °C obey the rate law [Formula: see text] where Ri is the rate of free-radical chain initiation. This order with respect to the styrene concentration implies extensive chain transfer from the poly(peroxystyryl)peroxy radical to a radical derived from the inhibitor. Reaction products confirm the displacement of a di-isopropyldithiophosphoryl radical in the chain termination reaction.Diethyldithiophosphoric acid also inhibits styrene autoxidation by a mechanism which involves extensive chain transfer.

The antioxidative-activity stability of aloe vera (Aloe vera var. chinensis) instant during storage

Food Research ◽  
2021 ◽  
Vol 5 (4) ◽  
pp. 288-293
Author(s):  
Riyanto ◽  
Ch. Wariyah
Keyword(s):  
Lipid Peroxidation ◽  
Critical Condition ◽  
Antioxidative Activity ◽  
Radical Scavenging ◽  
Aloe Vera ◽  
Oxygen Absorption ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Plastic Film ◽  
Lipid Peroxidation Inhibition

Aloe vera contains a phenolic compound that has bioactive activity. Previous research showed that microencapsulation of aloe vera powder with maltodextrin as an encapsulation agent produced instant aloe vera with high antioxidative activity. The problem was the hygroscopic instant caused rapid moisture and oxygen absorption during storage, therefore decreasing the instant aloe vera antioxidative activity periodically. The aim of this research was to evaluate the antioxidative activity stability of instant aloe vera during storage. The processing of instant aloe vera through a reconstituted aloe vera powder with water with a ratio of 1:120 and then added with 2.5% maltodextrin as the encapsulating agent. The solution was then inserted into a spray dryer with an inlet temperature of 130oC, an outlet temperature of 103oC, and the flow rate of the solution is 350.0 mL/h. The resulted instant aloe vera was divided into 15 packs with a weight of 25 g, and each sample was wrapped with polyethylene plastic film with 0.80 mm thickness and then was stored at 25oC with a relative humidity of 75%. The sample was conducted in triplicate. The moisture content, and antioxidative activity that was based on the ability to capture 1,1-diphenyl-2- picrylhydrazyl (DPPH) radical (RSA) and lipid peroxidation inhibition were analyzed every week until the critical condition was achieved at a moisture level of 12%. The research showed that the radical scavenging activity (RSA) and lipid peroxidation inhibition of instant aloe vera before storage were 16.34±1.22% and 39.33±1.68%, respectively, whereas in the critical condition the RSA was 3.63±0.04% and the lipid peroxidation inhibition was 22.31±0.02%. Based on their antioxidative activity, the appropriate storage time of instant aloe vera was about 12 weeks in polyethylene plastic film of 0.08 mm thickness

scholarly journals Antioxidant and Total Phenolic Content of Breadfruit (Artocarpus altilis) Leaves

2018 ◽  
Vol 150 ◽  
pp. 06007 ◽  
Author(s):  
Lee Yit Leng ◽  
Nuramira binti Nadzri ◽  
Khor Chu Yee ◽  
Norawanis binti Abdul Razak ◽  
Abdul Razak Shaari
Keyword(s):  
Antioxidant Activity ◽  
Total Phenolic Content ◽  
Phenolic Content ◽  
Copper Ions ◽  
Radical Scavenging ◽  
Chemical Components ◽  
Total Phenolic ◽  
Ftir Analysis ◽  
Artocarpus Altilis ◽  
Methanolic Extracts

This work aims to determine antioxidant, total phenolic content and Fourier transform infrared spectroscopy (FTIR) analysis of breadfruit leaves which are essential in management of diabetes. The methanolic extracts of breadfruit leaves was used to analyze for total phenolic content and antioxidant. Total phenolic content of the extracts was measured using the Folin–Ciocalteu assay while the antioxidant activity of plant extracts was measured by the 1, 1-diphenyl-2-picryhyradrazyl (DPPH) radical scavenging assay. FTIR analysis was used to determine the chemical components in the leaves. Total phenolic content in fresh breadfruit leaves (144.16 mg/g ± 17.98) was comparable to those of green tea. The results showed the breadfruit leaves extracts exhibited potent antioxidant activity. The presence of OH group also suggests antioxidant capacity of breadfruit leaves to deactivate free radicals as glucose itself could react with hydrogen peroxide in the presence of iron and copper ions to form hydroxyl radical.

Kinetics modeling in liquid phase sorption of copper ions on brushite di-calcium phosphate di-hydrate CaHPO4·2H2O (DCPD)

2014 ◽  
Vol 56 (3) ◽  
pp. 779-791 ◽  
Author(s):  
A. El Hamidi ◽  
R. Mulongo Masamba ◽  
M. Khachani ◽  
M. Halim ◽  
S. Arsalane
Keyword(s):  
Liquid Phase ◽  
Calcium Phosphate ◽  
Copper Ions ◽  
Kinetics Modeling

scholarly journals Isolation and Characterization of Alkyl Peroxy Radical Scavenging Compound from Leaves of Laurus nobilis

2002 ◽  
Vol 25 (1) ◽  
pp. 102-108 ◽  
Author(s):  
Hye Won Kang ◽  
Kwang Won Yu ◽  
Woo Jin Jun ◽  
Ih Seop Chang ◽  
Sang Bae Han ◽  
...  
Keyword(s):  
Radical Scavenging ◽  
Peroxy Radical ◽  
Laurus Nobilis ◽  
Isolation And Characterization ◽  
Alkyl Peroxy Radical

Autoxidation and Antioxidants. Basic Principles and New Developments

1974 ◽  
Vol 47 (4) ◽  
pp. 976-990 ◽  
Author(s):  
J. A. Howard
Keyword(s):  
Transition Metal Complexes ◽  
Radical Scavenging ◽  
Oxygen Radical ◽  
Basic Principles ◽  
New Developments ◽  
Chain Initiation ◽  
Elementary Reactions ◽  
Reasonable Degree ◽  
The Stability ◽  
Solid System

Abstract There is no doubt that liquid-phase hydrocarbon autoxidation is one of the most thoroughly understood reactions in organic chemistry. Our knowledge of the elementary reactions involved in this process is so complete that it should be possible to calculate, with a reasonable degree of precision, the overall rate of autoxidation of a hydrocarbon or mixture of hydrocarbons, provided, of course, that the rate of chain initiation can be estimated. It should also be possible to make a reasonable intelligent guess at the stability of a solid system, with the reservations appropriate to the change of phase. With regard to inhibition, there is probably not a great deal of room for further improvement in the inherent efficiency of H-atom donating antioxidants. This is because a decrease in the strength of the X—H bond makes the hydrogen more susceptible to abstraction by molecular oxygen. Radical scavenging transition metal complexes also suffer from the limitation that the more reactive the complex is to ROO the more reactive it will be to O2. There may, of course, be further improvements in the efficiency of preventative antioxidants, particularly multi-functional antioxidants with the ability to decompose hydroperoxides and peroxides by several non-radical mechanisms and also scavenge free-radicals.

The thermal decomposition of RDX at temperatures below the melting point. I. Comments on the mechanism

1970 ◽  
Vol 23 (4) ◽  
pp. 737 ◽  
Author(s):  
JJ Batten ◽  
DC Murdie
Keyword(s):  
Thermal Decomposition ◽  
Melting Point ◽  
Liquid Phase ◽  
Condensed Phase ◽  
Initial Rate ◽  
Decomposition Products ◽  
Sample Geometry

Two mechanisms have recently been proposed to explain the behaviour of the initial rate of decomposition of RDX, with change in sample geometry. These are (i)that the decomposition proceeds by concurrent gas and liquid phase reactions, and (ii) that gaseous decomposition products influence the rate of decomposition of undecomposed RDX in the condensed phase. In this paper it is concluded that mechanism (ii) is the more probable when the reaction is carried out in the presence of nitrogen.

Sign in / Sign up

Export Citation Format

Share Document