Diffusion coefficients of sodium dodecylsulfate in aqueous solutions and in aqueous solutions of β-cyclodextrin

Differential diffusion coefficients have been measured of sodium dodecylsulfate (SDS) in aqueous solutions of β-cyclodextrin (β-CD) at 298.15 K over the concentration range 0.001 M to 0.0817 M using a conductimetric cell and an automatic apparatus to follow the diffusion. The cell uses an open ended capillary method, while a conductimetric technique is used to follow the diffusion process by measuring the resistance of a solution inside the capillaries, at various recorded times. The β-CD is known to for strong 1:1 complexes with SDS, and the effect of this on the diffusion of this electrolyte was investigated. The presence of β-cyclodextrin can influence the diffusion coefficients of sodium dodecylsulfate both above and below the critical micelle concentration (cmc) of this surfactant. For concentrations of β-cyclodextrin of 0.001 mol dm⁻³ the behaviour of the diffusion of SDS in aqueous solutions is the same in the absence or the presence of β-cyclodextrin. In contrast, when the β-CD concentration is 0.016 mol dm⁻³ we obtain diffusion coefficients higher than those obtained in aqueous solutions. Further, we do not observe the dramatic decrease in diffusion normally found at the cmc of the surfactant. These results are interpreted in terms of the effect of incorporation of dodecylsulfate chains inside the cyclodextrin cavities.     

Dielectric behaviour of α-cyclodextrin,heptakis (2,3,6-tri-Omethyl)-β-cyclodextrin,randomly methylated β-cyclodextrin and low frequency Raman spectra of α- and β-cyclodextrins

The frequency and temperature dependence of the real (?′) and imaginary (?″)parts of the dielectric constant of α-cyclodrextrin (form 1; α-CD. 5.9H₂O) and α-cyclodextrin (form III; α-CD.7.6H₂O) and of the corresponding dried forms (α-CD.1.1H₂O, α-CD.2.9H₂O, respectively) has been investigated over the frequency range 0–100 k Hz and temperature range 130–350 K. In addition the dielectric behaviour has been investigated of heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (β-CD.TRIME. 0.3H₂O) and randomly methylated β-cyclodextrin (β-CD.RAME.0.8H₂O). The dielectric behaviour is described well by Debyetype relaxation (α-disperson). All α-CD systems exhibit an additional ω-dispersion at low frequencies, which is attributed to proton transport. The fact that the ?′ values of α-CD form III are larger than those of α-CD form I is attributed to the different numbers and different strengths of the intramolecular hydrogen bonds. Form III has a stable conformation which is shown by the constant values of ?′ in the temperature range 125–250 K. By contrast, in form I the ?′ values increased linearly with temperature, indicating that the system passed through succesive conformations. The temperature dependence of ?″ and phase shift ∞ in all the specimens of α-CD (forms I, III) and fully methylated β-CD do not reveal any orderdisorder transition, because the developed hydrogen bonds ae not of the flip-flop type according to their crystal structures. The partially methylated β-CD reveals the characteristics of the order-disorder transition, which was observed before in the systems dried β-CD.2H₂O and non-dried β-CD.9.8H₂O. There is a direct relation between the hydroxyl groups of β-CD and the order-disorder transition. The order-disorder transition could also be shown in dried β-CD.2.4H₂O and non-dried β-CD.9.8H₂O samples but not in dried α-CD.1.1H₂O and non-dried a-CD.5.9H₂O samples, by low frequency Raman spectroscopy (< 180 cm^?1). The step-like temperature dependence of the band at 33.7cm^?1 reveals a transition at about 223K for both β-CD samples. In the case of α-CD samples the almost linear temperature dependence of the band at 49.1 cm^?1 does not reveal any transition.     

Photophysical studies of xanthene dye in alkanols and in presence of inorganic ions

Eosin Y belongs to a xanthene group. It is an anionic fluorescent dye. The absorbance and fluorescence of Eosin Y have been investigated in a series of alkanols (methanol to propanol). When the solvents are added to the aqueous solution of Eosin Y (EY) the absorbance and fluorescence intensity are enhanced. The alkanols are found to affect the absorption and fluorescence spectra of the dye. On the basis of solvent adsorption model the binding constants of the dye with alkanols have been estimated. The interaction of solvent molecule with dye in aqueous solution is specific in nature. The fluorescence quenching of Eosin Y by the inorganic ions [Fe(CN)₆]⁻³, [Fe(CN)₆]⁻⁴ and Cl⁻ was also observed. The ions influenced the quenching process to different extents. The rate constants of quenching were calculated using the Stern-Volmer equation. The equilibrium constant of dye in presence of inorganic ions are determined by Scott equation.     

Effect of β-cyclodextrin, surfactants and solvent on the reactions of the recently synthesized Schiff base and its Cu(II) complex with cyanide ion

The kinetic of the reactions of the recently synthesized Schiff base (PABST) and its complex with Cu(II) (Cu-PABST) with CN⁻ in a 30:70 (v/v) mixture of DMF:water was investigated at pH 6.0 and 10.0, respectively, using multivariate curve resolution alternative least squares (MCR-ALS) method. The effects of different parameters such as volume percent of DMF, pH and surfactants and β-cyclodextrin (β-CD), on observed rate constant of the reactions were investigated. Cetyltrimethylammonium bromide (CTAB) decreased the rate constant of PABST reaction and increased the rate constant of Cu-PABST reaction with CN⁻. Sodium dodecyl sulfate (SDS) and Triton X-100 decreased the rate constant of both reactions. Also the stability constant for the inclusion complexes of PABST and Cu-PABST, and observed rate constants for the reactions of β-CD-PABST and β-CD-Cu-PABST) with CN⁻ were determined. β-CD decreased the rate constant of PABST reaction with CN⁻ by protecting iminium groups of the Schiff base, while β-CD increased the rate constant of the reaction of Cu-PABST with CN⁻.     

Dual fluorescence of dothiepin, doxepin drugs—effect of solvents and β-cyclodextrin

The absorption and fluorescence spectra of dothiepin and doxepin have been recorded in solvents of different polarities and β-cyclodextrin (β-CD). The inclusion complex of both drugs with β-CD is investigated by UV-visible, fluorimetry, DFT, FT-IR and scanning electron microscopy (SEM). In all solvents, the absorption and emission maxima of dothiepin are red shifted than doxepin. β-CD studies reveal that both drugs form a mixture inclusion complex with β-CD. The structured longer wavelength emission in β-CD aqueous solution suggests that viscosity plays major role in the β-CD. This study also confirms van der Waals forces and hydrophobic interactions are the driving forces for the inclusion complexes.     

Protonated dye-surfactant ion pair formation between neutral red and anionic surfactants in aqueous submicellar solutions

Spectral and surface tension behavior of aqueous neutral red in the presence of sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl sulfonate (SDSN) have been studied to understand the nature of the interactions in their submicellar concentration ranges. The variations in spectra and surface tension with variation in the concentrations of the surfactants suggest the formation of a 1:1 close-packed dye-surfactant ion pair, HNR⁺S⁻ between the acid form, HNR⁺ of the dye and the surfactant anion at very low concentrations of the surfactant below critical micelle concentration (cmc) of the pure surfactant. The dye-surfactant ion pair behaves like a nonionic surfactant having higher efficiency and lower cmc than that of the corresponding pure anionic surfactant. The ion pairs are adsorbed on the air/water interface at very low concentrations of the surfactant. As the concentration of the surfactant increases and the ion pairs form micelles of their own, the dye in the ion pair is protonated to form H₂NR²⁺S⁻. As the cmc of the pure surfactant is approached, the protonation equilibrium gradually reverses and pure surfactant ions gradually replace the ion pairs at the interface. Finally, a homogeneous monolayer of pure surfactant anions exists at the air/water interface and the dye remain solubilized in pure micelles above the cmc of the pure surfactant. The equilibrium constants, K_c for the close-packed protonated dye-surfactant ion pair (PDSIP) formation have been determined at varying pH. The submicellar interaction has been found to be stronger with SDS than SDBS. The plots of logarithm of K_c vs. pH have been found to be quite linear which consolidates the assumption of formation of the species, H₂NR²⁺S⁻. The interaction is driven by enthalpy as well as entropy.     

A study of fluorescence properties of citrinin in β-cyclodextrin aqueous solution and different solvents

Citrinin (CIT) is a nephrotoxic mycotoxin initially isolated from filamentous fungus Penicilliu citrinum. It was later isolated from several other species, such as Aspergillus and Monascus. It has a conjugated, planar structure that gives it a natural fluorescence ability, which can be used to develop sensitive methods for detecting CIT in food. In this paper, we used the spectro?uorescence technique to study the effects of pH value, β-cyclodextrin (β-CD) and organic solvents on the CIT fluorescence intensity. The results show that lower pH value, aceitc acid, β-CD and acetonitrile can induce a higher fluorescence intensity of CIT, but methanol or H₂O has a decreasing effect on the fluorescence intensity of CIT. Findings in this study provide a theoretical basis for development of a high sensitivity fluorescence-based trace analysis for CIT detection.     

Dielectric behaviour and hydrogen bond molecular interaction study of formamide-dipolar solvents binary mixtures

The dielectric constant of binary mixtures of formamide with some common dipolar aprotic and protic solvents has been investigated at sixteen molar concentrations over the entire mixing range at 30 °C. The solvents used for binary mixtures with formamide are water, dimethylsulphoxide, N,N-dimethylformamide, acetone, 1,4-dioxane, mono-, di- and trihydric alcohols, and homologous series of 2-alkoxyethanol, 2-(2-alkoxyethoxy)ethanol, and ethylene glycol oligomers. The concentration dependent plots of excess dielectric constant and Kirkwood correlation factor were used to explore the complexes formed between unlike molecules, the molar ratio of a stable adduct, dipolar ordering, hydrogen-bond molecular connectivities, and their strength in the binary mixtures. Results confirmed that the complexation strength of dipolar aprotic solvents with formamide strongly depends on the value of solvent dielectric constant. The dependence of the hydrogen-bond complexation on number of hydroxyl groups and molecular size of the homologous series of the solvents is recognized from the comparative excess dielectric constant values of the mixed solvents.     

Photophysics of two structurally similar dyes containing substituted amino as donor and carbonyl as acceptor groups

The present work entails a comparative photophysical study of two structurally similar donor–acceptor dyes. In one of the dyes (DN2) twisting about C–N bond is permissible, while twisting is strategically restricted in the other (N2). Optical responses of both the dyes have been monitored in pure and mixed binary solvents comprising of mainly aprotic+protic systems. Results indicate that the nature of emitting states in protic and aprotic microenvironments is different for the two dyes. In aprotic media the solvated dye molecule is the emitting species while emission mainly takes place, supposedly, from the dye-solvent hydrogen bonded complex in protic media. The parallel behaviour of the two dyes indicates that twisting about C–N bond in the excited state is not an important photophysical process. Further, the effect of addition of strong acid to the dye solution and the corresponding existence of equilibrium between two tautomeric forms for both the dye has been studied.     

Spectrofluorometric investigation of salicylal- dithiocarbazinic acid esters

The fluorescent properties of salicylaldithiocarbazinic esters which can be described by RR¹C= N-NH-CSSR² (where R = 0HO-C₆H₄; R¹ = H or CH₃; R² =CH₃, C₆H₅-CH₂ or p-C1-C₆H₄-CH₂) have been investigated.The investigations were made in DMF, in different DMF-water mixtures, and in aqueous media. It could be stated that the change of the R² group has an unimportant effect on the intensity of fluorescence and on the excitation and emission spectra in all examined solvents. But an important effect is caused by the change of the group R¹. As in DMF solution, only the excitation spectrum changes on substituting R¹ = H by R¹ = CH₃, in DMF: water i.e. aqueous media, the change in the intensity of fluorescence, too, is very great.In the case of R¹ = H, the intensity of fluorescence is about five times greater than in R¹ = CH₃. The intensity of fluorescence can be increased, if an electrophil substituent is put into the place of group R¹.     

Encapsulation of nabumetone by means of -drug: (β-cyclodextrin)2:polyvinylpyrrolidone ternary complex formation

The aim of the present study was to investigate the effect of the presence of the water-soluble polymer polyvinylpyrrolidone (PVP) MW=24,000 g/mol, on the complexing of the anti-inflammatory drug nabumetone, with β-cyclodextrin (β-CD). The data show that the polymer interacts with the free nabumetone and with the nabumetone:β-CD inclusion complex, in both cases with a stoichiometry of 1:1. The interaction constants are 1.3×10⁴ M⁻¹ and 1.6×10⁴ M⁻¹, respectively.The presence of PVP, changes the drug:cyclodextrin interaction, a nabumetone:(β-CD)₂:PVP complex being formed.In addition, the presence of PVP, produces a strong increase in the global binding constant, β₂=(22.12±0.22)×10⁶ M⁻² at 1% PVP.In the ternary complex, the nabumetone is wrapped at both ends for the β-CD. In this complex the polymer seems to act as a bridge between both β-CD molecules that bind the nabumetone.     

HP-β-CD消除SDS对SDBS同步荧光光谱的影响

十二烷基苯磺酸钠(SDBS)与十二烷基苯磺酸钠(SDS)之间的相互作用,能对SDBS的检测产生明显干扰。实验结果表明,在水溶液中SDS不仅可以增大SDBS的同步荧光强度,还能显著降低SDBS的表观临界胶束浓度。按SDBS的摩尔计量比加入1∶1的羟丙基-β-环糊精(HP-β-CD),可以消除SDS对SDBS的同步荧光强度的干扰。相比于形成胶束,在SDS/SDBS水溶液中,SDBS单体优先选择与HP-β-CD形成量比1∶1的包结物。当水溶液中HP-β-CD的浓度由0增加至0.900 mmol·L~(-1)时,复配体系中SDBS形成胶束的标准摩尔吉布斯函变ΔγGθm由-39.681 k J·mol-1增加至-37.580 k J·mol~(-1)。加入适量HP-β-CD后,能够准确检测SDS/SDBS水溶液中SDBS的含量(临盘采油厂T5站地层水样),方法的回收率为101.0%~101.6%。FT-IR及1H-NMR分析表明,SDBS分子进入HP-β-CD分子内腔的大口径端并形成量比1∶1的包结物,是消除SDS对SDBS检测干扰的根本原因。     

Determination of Aluminum Ion with Morin in a Medium Comprised by Ionic Liquid?CWater Mixtures

In this study we have employed two ionic liquids (ILs) as a new media for the analysis of aluminum in aqueous solutions by spectrofluorimetric method. ILs are liquid salts and they have no measurable vapor pressure up to their thermal decomposition point, >300 ??C. This lack of vapor pressure makes these materials highly attractive for many studies as they can be used as clean solvents. Besides they are promising environments for analysis purposes and optical sensor designs. The results revealed that absorption, excitation and emission spectra of the morin?CAl complex exhibited considerable changes in moieties. The morin?CAl complex was stable at aluminum concentrations below 9.1?mg?L^?1 in 25% 1-butyl-3-methylimidazolium bromide (IL-I)-water binary mixtures. The higher concentrations of IL (>25% by volume) was not suitable for the complex formation thus in pure IL media the complex formation even at high aluminum concentrations was not observed. The complex stoichiometry ratio of aluminum:morin was 2:1 in IL-I-water binary mixtures. The linear concentration range was 0.045?C7.2?mg?L^?1 with a correlation coefficient of r?=?0.9909. The detection limit was found to be 0.036?mg?L^?1. Cu²⁺, Mn²⁺ and PO ₄ ^3? ions exhibited less interfering effect in presence of IL-I and the tolerance limit of Cu enhanced 10 times when compared with ethanol.     

Photophysical parameters and fluorescence quenching of 7-diethylaminocoumarin (DEAC) laser dye

The optical properties including electronic absorption spectrum, emission spectrum, fluorescence quantum yield, and dipole moment of electronic transition of 7-diethylaminocoumarin (DEAC) laser dye have been measured in different solvents. Both electronic absorption and fluorescence spectra are red shifted as the polarity of the medium increases, indicating that the dipole moment of molecule increases on excitation. The fluorescence quantum yield of DEAC decreases as the polarity of solvent increases, a result of the role of solvent polarity in stabilization of the twisting of the intramolecular charge transfer (TICT) in excited state, which is a non-emissive state, as well as hydrogen bonding with the hetero-atom of dye. The emission spectrum of DEAC has also been measured in cationic (CTAC) and anionic (SDS) micelles, the intensity increases as the concentration of surfactant increases, and an abrupt change in emission intensity is observed at critical micelle concentration (CMC) of surfactant. 2×10⁻³ mol dm⁻³ of DEAC gives laser emission in the blue region on pumping with nitrogen laser (λ_ex=337.1 nm). The laser parameters such as tuning range, gain coefficient (α), emission cross section (σ_e), and half-life energy have been calculated in different solvents, namely acetone, dioxane , ethanol, and dimethyforamide (DMF). The photoreactivity of DEAC has been studied in CCl₄ at a wavelength of 366 nm. The values of photochemical yield (?_c) and rate constant (k) are determined. The interaction of organic acceptors such as picric acid (PA), tetracyanoethylene (TCNE), and 7,7,8,8-tetracynoquinonedimethane (TCNQ) with DEAC is also studied using fluorescence measurements in acetonitrile (CH₃CN); from fluorescence quenching study we assume the possible electron transfer from excited donor DEAC to organic acceptor forming non-emissive exciplex.     

Photophysical properties of a surfactive long-chain styryl merocyanine dye as fluorescent probe

This work deals with detailed investigations of the photophysical properties of a styryl merocyanine dye, namely 1-cetyl-4-[4′-(methoxy) styryl]-pyridinium bromide (CMSPB) of molecular rotor type. The solvatochromic analyses of the data in different solvents using the Kamlet-Taft parameters (α, β, π^?) were discussed. Optical excitation of the studied merocyanine dye populates a CT S₁ state with about 22.64 folds higher dipole moment value relative to that in the S₀ state. Moreover, the effect of solvent viscosity (glycerol at various temperatures (299.0–351.0 K)) on CMSPB fluorescent properties is analyzed to understand the molecular mechanisms of the characteristic increase in CMSPB fluorescence intensity. The results indicate that CMSPB exhibits fluorescent properties typical for molecular rotors. The results show that torsional relaxation dynamics of molecular rotors in high-viscosity solvents cannot be described by the simple stick boundary hydrodynamics defined by the Debye–Stokes–Einstein (DSE) equation. The fluorescence depolarization behavior in glycerol at various temperatures (299.0–351.0 K) shows that the molecular rotational diffusion is controlled by the free volume of the medium. Furthermore, excited state studies in ethanol/chloroform mixture revealed the formation of weak complex with chloroform of stoichiometry 1:1 with formation constant of 0.004l mol^?1. Moreover, the increase of the quantum yield values in micellar solutions of CTAB and SDS relative to that of water indicates that the guest dye molecules are microencapsulated into the hydrophobic interior of host micelle. The obtained non-zero values of fluorescence polarization in micellar solution imply reduced rotational depolarization of dye molecules via association with the surfactant. Upon comparing the spectral data in micelles with those in homogeneous solvent systems, more can be learned of the structural details of the micellar environment, which have often been used as models for more complex bioaggregates. The results point out to a possible use of this dye as a fluorescence probe for microenvironmental parameters as well as in some micellar systems.     

Atomic Shell Recovery Times Following 181Hf β−-Decay

Systematic measurements of perturbed angular correlation (PAC) for the 133–482 keV cascade of ¹⁸¹Ta have been performed in the viscous media of glycerol, diethylene glycol and ethylene glycol. The similar PAC spectra observed and the same values of different parameters like quadrupole frequency, relaxation constant and anisotropy parameter found (within errors) confirm atomic “after effects” following β^?-decay of ¹⁸¹Hf in these media. The PAC measurements have also been performed in these media at different viscosities by adding H₂O. For the glycerol-H₂O system, it is found that atomic recovery time do not changes in the viscosity range of greater than 5 mPa?s. In this range of viscosity, the recovery time was measured to be ～50 nsec. In the low viscosity region (≤2 mPa?s), however, the atomic recovery process becomes faster. In case of diethylene glycol-H₂O and ethylene glycol-H₂O systems also, it is found that atomic recovery times becomes smaller in the low viscosity region.     

Fluorescence quenching of 3,7-diamino-2,8-dimethyl-5-phenyl phenazinium chloride by AgCl and Ag nanoparticles

Quenching of fluorescence of the dye 3,7-diamino-2,8-dimethyl-5-phenyl Phenazinium Chloride (Safranine T) has been investigated by AgCl nanoparticles in the W/O microemulsion medium at different [H₂O]/[AOT] ratios (ω) and with Ag nanoparticles and Ag⁺ in aqueous medium. A simple straightforward method has been introduced to prepare AgCl nanoparticles in well-characterized, monodispersed biomimicking nanocavities formed by sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in heptane. Experimental results reveal that the size of the AgCl nanoparticles increases with increase in hydration. The results of the quenching experiment were analysed in the light of Stern Volmer equation. Quenching of fluorescence of the dye has been found to decrease with decrease in the size of the nanoparticles of AgCl and the variation of Stern Volmer quenching constants (K_SV) with particle size is different for two different size regimes.     

Correlation of dielectric properties,Raman spectra and calorimetric measurements of β-cyclodextrin-polyiodide complexes (β-cyclodextrin)2 ·BaI7 ·11H2O and (β-cyclodextrin)2 ·CdI7·15H2O

The frequency and temperature dependence of real and imaginary parts of the dielectric constant (ε′,?ε″), the phase shift (?) and the ac-conductivity (σ) of polycrystalline complexes (β-CD)₂·BaI₇·11H₂O and (β-CD)₂·CdI₇·15H₂O (β-CD?=?β-cyclodextrin) has been investigated over the frequency and temperature ranges 0–100?kHz and 140–420?K in combination with their Raman spectra, DSC traces and XRD patterns. The ε′(T), ε″(T) and ?(T) values at frequency 300?Hz in the range T<330?K show two sigmoids, two bell-shaped curves and two minima respectively revealing the existence of two kinds of water molecule, the tightly bound and the easily movable. Both complexes show the transition of normal hydrogen bonds to flip-flop type at 201?K. In the β-Ba complex most of the eleven water molecules remain tightly bound and only a small number of them are easily movable. On the contrary, in the β-Cd case the tightly bound water molecules are transformed gradually to easily movable. Their DSC traces show endothermic peaks with onset temperatures 118°C, 128°C for β-Ba and 106°C, 123°C, 131°C for β-Cd. The peaks 118°C, 106°C, 123°C are related to the easily movable and the tightly bound water molecules, while the peaks at 128°C, 131°C are caused by the sublimation of iodine. The activation energy of Ba²⁺ ions is 0.52?eV when all the water molecules exist in the sample and 0.99?eV when the easily movable water molecules have been removed. In the case of β-Cd the corresponding activation energies are 0.57?eV and 0.33?eV. The Raman peaks at 179?cm^?1, 170?cm^?1 and 165–166?cm^?1 are due to the charge transfer interactions in the polyiodide chains.     

Characterization of mixed micelles of sodium cumene sulfonate with sodium dodecyl sulfate and cetyl trimethylammonium bromide by SANS,FTIR spectroscopy and NMR spectroscopy

The aqueous solutions of sodium cumene sulfonate (NaCS) and its mixtures with cetyl trimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) are studied by Small Angle Neutron Scattering (SANS), Fourier Transform Infrared (FTIR) spectroscopy and Nuclear Magnetic Resonance (NMR) spectroscopy. The compositions of mixed micelles are determined using Rubingh's Regular Solution Theory. NaCS when added to CTAB solution leads to the formation of long rod shaped micelles with dramatic increase in the CTAB aggregation number. Its addition to SDS on the other hand results in the formation of smaller mixed micelles where parts of SDS molecules in the micelle are replaced by NaCS molecules. NaCS–SDS mixed micelles prefer elongated ellipsoidal geometry in order to accommodate short NaCS molecules. The FTIR spectroscopy results indicate enhanced ordering of CTAB tails inside the NaCS–CTAB mixed micelles with reduction in the gauche/trans conformer ratio. Addition of NaCS to SDS on the other hand results in decreased ordering of SDS tails, as compared to SDS micelles alone. The chemical shifts observed in ¹H NMR spectra of NaCS–SDS and NaCS–CTAB mixture indicate that NaCS resides near the surface of the SDS micelle.     

On the hydroperoxyl radical scavenging activity of two Edaravone derivatives: mechanism and kinetics

The free radical scavenging activity of two Edaravone (EDA) derivatives (C1 and D1) has been studied in aqueous and lipid solutions using the Density Functional Theory. Different mechanisms of reaction have been considered, as well as the acid/base equilibrium in aqueous solution. The studied compounds were found to be rather poor ^?OOH scavengers in non‐polar environments, but better than the parent molecule, EDA, which suggests that the peroxyl scavenging activity of this kind of compounds in lipid media could be increased via structural modifications. In aqueous solution, at physiological pH, D1 is predicted to be a better peroxyl scavenger than C1, and slightly better than its parent molecule, EDA. Their excellent activity, under such conditions, is attributed to the electron transfer from their anionic forms. D1 was found to be among the best peroxyl scavengers known so far, with a rate constant for its reaction with ^?OOH near the diffusion limit regime (2.3 × 10⁸ M^?1s^?1). Copyright © 2013 John Wiley & Sons, Ltd.