The reactivity of p-nitrophenyl esters with surfactants in apolar solvents. VI. Structural effects on the reaction of p-nitrophenyl acetate with alkanediamine bis(dodecanoate) salts

1983 ◽  
Vol 36 (5) ◽  
pp. 907 ◽  
Author(s):  
CJ O'Conner ◽  
TD Lomax
Keyword(s):  
Chain Length ◽  
Rate Constant ◽  
Structural Effects ◽  
Detergent Concentration ◽  
Bimolecular Rate Constant ◽  
Head Groups

The rate of decomposition of p-nitrophenyl acetate has been measured in benzene solutions of a series of alkane-α,ω-diamine bis(dodecanoate) salts. Me(CH2)10CO2-+NH3(CH2)NH3N+ -O2C(CH2)10ME(n=2-7,9,10,12) The micellar rate constant is affected by the diamine chain length, and the bimolecular rate constant is affected both by the chain length (and whether the number of carbon atoms is even or odd) and by the acidity of the diammonium head groups. The Br�nsted plot is linear but the slope in creases with increasing detergent concentration.

The reactivity of p-nitrophenyl esters with surfactants in nonaqueous solvents. III. The effect of altering the head-groups of alkylammonium carboxylates dissolved in benzene

1980 ◽  
Vol 33 (4) ◽  
pp. 779 ◽  
Author(s):  
CJ O'Conner ◽  
RE Ramage
Keyword(s):  
Chain Length ◽  
Rate Constant ◽  
Alkyl Chain ◽  
Alkyl Chain Length ◽  
Nonaqueous Solvents ◽  
Bimolecular Rate Constant ◽  
Head Groups

The rate of decomposition of p-nitrophenyl acetate, pnpa, has been measured in benzene solutions of a series of alkylammonium propionates, CH3(CH2),NH3+ -O2CCH2CH3 (where n = 3, 5, 7, 9 or 11), and a series of dodecylammonium carboxylates, CH3(CH2)11NH3+ -O2C(CH2)mCH3 where m = 1, 2, 6 or 7). The micellar rate constant is affected by the alkyl chain length. The bimolecular rate constant is affected by both the chain length and the acidity of the head-groups. The reactivity of longer chain esters with dodecylammonium propionate is markedly less than that of pnpa.

The reactivity of p-nitrophenyl esters with surfactants in nonaqueous solvents. II. The effects of added water in benzene solutions of dodecylammonium propionate, and the reaction in toluene and cyclohexane

1980 ◽  
Vol 33 (4) ◽  
pp. 771 ◽  
Author(s):  
CJ O'Conner ◽  
RE Ramage
Keyword(s):  
Rate Constant ◽  
Rate Equation ◽  
Surfactant Concentration ◽  
Nonaqueous Solvents ◽  
Base Catalysis ◽  
Head Group ◽  
Bimolecular Rate Constant ◽  
General Base ◽  
Head Groups ◽  
Added Water

The rate of decomposition of p-nitrophenyl acetate, pnpa, in benzene containing up to 0.11 mol dm-3 of solubilized water in the presence of dodecylammonium propionate, dap, has been measured at 298 K. Although the micellar rate constant is decreased due to hydration of the head- groups, the bimolecular rate constant due to general acid-general base catalysis from the head-group components of dap is unchanged. There is no evidence to suggest that the substrate undergoes hydrolysis. Changing the solvent to either toluene or cyclohexane increases the micellar rate constant and changes the second term in the rate equation to one which includes the square of the surfactant concentration.

From Reduction to Oxidation: pH Controlled Reaction of 1 Hydroxyethyl Radical with Caffeic Acid Analogues.

2021 ◽  
Vol 11 ◽  
Author(s):  
Laboni Das ◽  
Shashi P Shukla ◽  
Suchandra Chatterjee ◽  
Ashis K Satpati ◽  
Soumyakanti Adhikari
Keyword(s):  
Caffeic Acid ◽  
Rate Constant ◽  
Reduction Process ◽  
Phenoxyl Radical ◽  
Alpha Tocopherol ◽  
Side Chain ◽  
Product Analysis ◽  
Bimolecular Rate Constant ◽  
Ethyl Radical ◽  
Computational Calculations

Aims: The aim is to search for newer and better antioxidants through kinetic spectroscopic studies in combination with product analysis and computation. Background: Antioxidant effect of caffeic acid, its derivative, and analogues have been well reported. The antioxidative efficiencies are related to their molecular structure, and two reaction pathways are well accepted, H-atom transfer (HAT) or single electron transfer. 1-hydroxy ethyl radical (1-HER) being an ethanol-derived free radical might be causing the onset of liver injury detected after alcohol administration. 1-HER has also been reported to react with fatty acids and endogenous antioxidants such as glutathione, ascorbic acid, and alpha-tocopherol Objective: The present study is an attempt to understand the reaction mechanism of 1-HER with caffeic acid, its derivative, and analogues in detail. Method: Pulse radiolysis with kinetic absorption spectroscopy has been employed to follow the reaction pathway and identify the intermediates produced in the reaction. The reaction products have been detected using LCMS/MS. Based on these studies, a consolidated mechanism has been proposed. Cyclic voltammetry measurements and computational calculations have been used in support of the proposed mechanism. Result: In the reaction of 1-hydroxy ethyl radical (1-HER) with caffeic acid and its oligomers, reduction takes place below the pKa1, while oxidation occurs with the deprotonated phenolic moiety. The reduction of caffeic acid generates a carbon-centered radical at the double bond of the side chain with a bimolecular rate constant of 1.5x1010 dm3 mol-1 s-1. Notably, a low concentration of oxygen was able to regenerate a part of the caffeic acid molecules in the reduction process. At pH 10 a phenoxyl radical is formed due to oxidation with a much lower bimolecular rate constant (4.2x108 dm3 mol-1 s-1). In the case of di-hydrocaffeic acid, only phenoxyl radical is formed at pH 10 and, no reaction could be observed below pH 8. Conclusion: Change in reactive pattern from reduction to oxidation with change in pH within the same set of reactants has been evidently established in the present study. The results point towards the importance of  unsaturation in the side chain of caffeic acid oligomers for their reaction with 1-HER at neutral pH. The effect of oxygen concentration on the antioxidative protection offered by this class of molecules might be intriguing for the quest of the effectiveness of antioxidants at low concentrations. Other: It may be inferred that the effect of pH on the reactivity pattern as observed is not 1-HER, but substrate-specific, in the present case, phenolic acids. This study generates further scope for in-depth studies on other polyphenols where unsaturation exists in the side chain.

scholarly journals THE RATE CONSTANT OF THE REACTION BETWEEN FERROUS IONS AND HYDROGEN PEROXIDE IN ACID SOLUTION

1957 ◽  
Vol 35 (5) ◽  
pp. 428-436 ◽  
Author(s):  
T. J. Hardwick
Keyword(s):  
Hydrogen Peroxide ◽  
Acid Solution ◽  
Sulphuric Acid ◽  
Acid Concentration ◽  
Rate Constant ◽  
Perchloric Acid ◽  
Ferrous Ion ◽  
Ferrous Ions ◽  
Bimolecular Rate Constant

Identical values of the bimolecular rate constant of the ferrous ion – hydrogen peroxide reaction were obtained from intercomparisons of the methods previously used in following this reaction. In perchloric acid the bimolecular rate constant is unaffected by acid concentration; in sulphuric acid it increases slightly in acid concentrations above 10−2N. The results agree with and explain the differences between those obtained by Baxendale and by Dainton, but are only in marginal agreement with those recently reported by Weiss.

Thermodynamics of micellization and solubilization in systems of water – sodium n-alkylcarboxylates – alkoxyethanols at 25 °C

1997 ◽  
Vol 75 (11) ◽  
pp. 1445-1462 ◽  
Author(s):  
H. Huang ◽  
R.E. Verrall
Keyword(s):  
Aqueous Solutions ◽  
Distribution Coefficient ◽  
Chain Length ◽  
Transfer Functions ◽  
Mass Action ◽  
Sodium Carboxylate ◽  
Medium Chain Length ◽  
Head Groups ◽  
Action Model ◽  
State Formula

The apparent molar volumes and adiabatic compressibilities, [Formula: see text] of carboxylate surfactants, CnNa (n = 8, 10, 12), in aqueous solutions in the absence and presence of medium-chain-length alkoxyethanols, C4EOX (EO = ethylene oxide group, X = 0–4), and of alkoxyethanols, [Formula: see text] in aqueous solutions in the absence and presence of surfactant, were determined at 25 °C from density and sound velocity measurements as a function of both the surfactant and alcohol concentrations. The partial molar volumetric properties of CnNa and the transfer functions of C4EOX from water to aqueous surfactant solutions were calculated from the apparent molar properties. Values of the thermodynamic parameters of micellization for CnNa, i.e., the critical micelle concentration, the partial molar property of the monomer at infinite dilution, [Formula: see text] and in the micellar state, [Formula: see text] were obtained from simulations of the experimental data, [Formula: see text] using a mass-action model. As expected, these properties are strongly dependent on the surfactant chain length. The distribution coefficient of C4EOX between the micelle and aqueous phases, KD, and the change in the molar property of alcohols due to micellization, [Formula: see text] extracted from fitting the transfer function data of C4EOX using a chemical equilibrium model, show that the solubilization of alkoxyethanols in carboxylate micelles is enhanced by increasing the surfactant chain length and the number of EO groups in the alcohol. The deeper penetration of C4EOX into the micelles of longer chain surfactants is associated with increasingly stronger interactions between surfactant head groups and EO segments of the alcohol on (or near) the micelle surface. Aggregation numbers of CnNa–C4EOX mixed micelles show that addition of a small amount of C4EOX has little effect on the structure of the micelles formed from C8Na and C10Na, but leads to significant change in C12Na micelles. Keywords: sodium carboxylate salts, alkoxyethanols, partial molar volume and compressibility, transfer functions, distribution coefficient, mean aggregation number.

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