Hydroxamate Ions Research Articles

Analysis of the Experimental Data of Acid Hydrolysis in Micelle Assemblies Using Kinetic Model

Acid Hydrolysis of carboxylate ester with hydroxamate ions in micellar media has been discussed in our last research works. In this paper, we used all the obtained kinetic experimental data for correlation and explanation by modeling techniques. We know the different types of modeling techniques available and used in the current times. Michael menten one site total binding constant and one site fite Ki models apply for the explanation of kinetics data. The models were given a good explanation and correlation of these types of kinetic data.

Spot test exploiting smartphone-based digital images for determination of biodiesel in diesel blends

A simple, inexpensive, and fast colorimetric spot test is proposed for quantification of biodiesel in diesel blends. The procedure was based on formation of a violet complex between Fe(III) and the hydroxamate ion generated by the reaction of the alkyl esters characteristic of biodiesel with hydroxylamine. The analytical measurements were based on digital images acquired using a smartphone camera and converted to RGB values using a free application software (PhotoMetrix® 1.6). Values of the G channel corresponding to the intensities of the reflected radiation were taken as analytical parameter because of the complementarity with the absorption spectrum of the Fe(III)/hydroxamate complex. The effects of the reagents concentrations were evaluated by a Box-Bhenken experimental design and the optimized condition was 0.20 mol L−1 hydroxylamine, 0.30 mol L−1 NaOH, and 5.0 mmol L−1 Fe2(SO4)3. A linear response range was achieved from 3.0 to 30.0% (v/v) of biodiesel, described by equation G = 59.4 + 1.72 C (r = 0.999). The coefficient of variation and the limit of detection (99.7% confidence level) were estimated at 0.9% (n = 10) and 1.0% (v/v) of biodiesel, respectively. The proposed procedure consumed only 10 µL of sample, 830 μg NH2OH.HCl, and 110 μg Fe(III) and generated ca. 1.0 mL of residue per determination. The results for determination of biodiesel in diesel blends agreed with those obtained by the official method EN14078 at the 95% confidence level. The proposed procedure also allows monitoring formation of fatty acid methyl esters during the transesterification reaction.

Cytotoxicity and -glucosidase inhibition studies of Cu(II) and Ni(II) salicylhydroxamic acid complexes

Hydroxamic acids (RCONHOH) are weak acids that can exist naturally or synthetically. These acids are easy to deprotonate and produce hydroxamate ions. The syntheses, physico-chemical and characterization of salicylhydroxamic acid (SHA) and its copper(II) and nickel(II) complexes were reported herein. The metal complexes were synthesized by condensation reaction of SHA with metal salts in 2:1 molar ratio. SHA and its metal complexes were characterized by elemental analysis, infrared spectroscopy, 1 H and 13 C NMR, UV-Vis, TGA, magnetic susceptibility and molar conductance. From IR and magnetic susceptibility, each complexes coordinated to the metal via oxygen atoms ( O,O ) in a bidentate manner to form octahedral geometries. The molar conductance values suggested that all complexes were non-electrolytes. A cytotoxicity study against HCT116 displayed that Cu(II) and Ni(II) complexes have better anticancer than their parent ligands, SHA but not categorized as potent anticancer agents. Both complexes have better inhibition towards a-glucosidase compared to acarbose, suggesting that Cu(II) and Ni(II) complexes have potential as antidiabetic agents.

Hydrolytic Dephosphorylation of p‐Nitrophenyl Diphenyl Phosphate by Alkyl Hydroxamate Ions

AbstractThe kinetics of the hydrolysis of p‐nitrophenyl diphenyl phosphate (PNPDPP) by hydroxamate ions (R'(CO)N(RO−) such as octanohydroxamate (OHA−) and decanohydroxamate (DHA−) was investigated in dioctadecyldimethylammonium chloride (DODAC) and didodecyldimethylammonium bromide (DDAB) vesicles. The physicochemical properties of these surfactants were studied by conductivity and fluorescence measurements at 300 K. The hydrolysis of PNPDPP was studied in a vesicular system by using hydroxamate ions (OHA− and DHA−) at 300 K. The different catalytic effects of hydroxamate ions for the hydrolysis of PNPDPP in the vesicles were determined. All reactions followed pseudofirst‐order kinetics. The reactivity of DHA− was found to be higher than that of OHA− in the vesicular system toward the cleavage of phosphate ester. Further, the binding constants (K) and free energy change (∆G) for the associations of PNPDPP with DODAC and DDAB vesicles were determined spectrophotometrically as well as from the Benesi–Hildebrand (B–H) plots. The pseudophase model was applied for the quantitative treatment of the kinetic data in the vesicle systems.

An investigation of kinetic and physicochemical properties of vesicular surfactants with oximate and hydroxamate ions: Hydrolytic reactions of organophosphorus pesticides

Rate constants have been determined spectrophotometrically for the reaction of paraoxon, parathion and fenitrothion (OP pesticides) with oximate (Ox−) and hydroxamate (HA−) ions in aqueous and cationic vesicular media at 300K. All reactions followed the pseudo-first-order kinetics. The surface properties i.e. the critical vesicle concentration (cvc), maximum surface access (Γmax), surface pressure at the cvc (Πcvc) and minimum surface area per molecule (Amin) of vesicular surfactants dioctadecyldimethylammonium chloride (DODAC) and didodecyldimethylammonium bromide (DDAB) with Ox− and HA− ions have been evaluated by conductivity and surface tension measurements at 300K. The standard Gibbs free energy of vesicle formation (ΔG0v), Standard Gibbs free energy of adsorption (ΔG0ad), and standard Gibbs free energy of vesicle formation per alkyl chain (ΔG0v, tail) of cationic vesicular surfactants with Ox− and HA− ions have also been evaluated. SEM (Scanning Electron Microscope) and TEM (Transmission Electron Microscope) were used to investigate the morphological behavior and size of vesicular surfactants. We observed a well-defined contour of vesicular surfactants that are mostly spherical and globular shape. The effects of vesicular morphology and chemical reactivity have been discussed.

Synthesis and Spectroscopic Analysis of the Nature of Coordination Modes of Ligands in Copper (ll) and Cadmium (ll) Complexes of Two N-Oxidobenzamide Derivatives

N-Oxidobenzamide derivatives are powerful metal ion chelators. It is used as inhibitors of hypertension, tumor growth, inflammation, infectious agents, asthma, arthritis, Alzheimer’s diseases and more. In this study, Copper (ll) (SRC1 and SRC3) and Cadmium (ll) (SRC2 and SRC4) complexes were synthesized from potassium N-Oxidobenzamide derivative ligands and they were characterized by using various techniques such as Infra-Red spectra, electronic spectra, melting point and conductivity measurements. The electronic spectral study and the melting point analysis revealed that the ligands are coordinated to the metal centre. IR and conductivity analyses confirm the coordination of hydroxamate ions to the metal centre as O, O-bidentate mode via the hydroxyl oxygen and the carbonyl oxygen atoms of the ligands. The proposed molecular structures for the newly formed complexes are also given.

Reactivity of Hydroxamate Ions in Cationic Vesicular Media for the Cleavage of Carboxylate Esters

AbstractThe hydrolysis of carboxylate esters viz. p‐nitrophenyl acetate (PNPA), p‐nitrophenyl butyrate (PNPB) and p‐nitrophenyl octanoate (PNPO) in the presence of cationic vesicles of the surfactant dioctadecyldimethylammonium bromide (DODAC) by different hydroxamate ions i.e. acetohydroxamate (AHA−), benzohydroxamate (BHA−) and salicylhydroxamate (SHA−) were studied. The kinetic data was supported by spectrophotometric measurements. The effects of vesicular size on the reaction have been discussed. The differential reactivity under endo‐ and exovesicular conditions has also been evaluated. Critical vesicle concentrations (CVC) of cationic vesicular surfactants were determined from conductometric and fluorimetric measurements at 300 K. Fluorescence probe pyrene and pyrene‐1‐carboxaldehyde have been used for determination of CVC. Further, thermodynamic parameters viz. Standard Gibb's energy (∆G°), enthalpy (∆H°), and entropy (∆S°) of vesicles has also been evaluated within a temperature range of 303.15–328.15 K.

Flotation behavior and adsorption mechanism of fine wolframite with octyl hydroxamic acid

Flotation behavior and adsorption mechanism of octyl hydroxamic acid (OHA) on wolframite were investigated through flotation experiments, adsorption tests, zeta-potential measurements, infrared spectroscopy and solution chemistry calculations. Results of flotation and adsorption experiments show that the maximum values of flotation recovery and adsorption capacity occur around pH 9. In term of the solution chemistry calculations, the concentration of metal hydroxamate is greater than that of metal tungstate and metal hydroxyl, and metal hydroxamate compounds are identified to be the main species on wolframite surface at pH region of 8-10, contributing to the increase of OHA adsorption and flotation performance. Results of zeta-potential and IR spectra demonstrate that OHA adsorbs onto wolframite surface by chemisorptions. Hydroxamate ions can bond with Mn2+/Fe2+ cations of wolframite surface, forming metal hydroxamate compounds, which is a key factor in inducing the hydrophobicity of wolframite under the conditions of maximum flotation.

Nucleophilicity of aromatic and aliphatic hydroxamate ions towards C=O and P=O center in cationic micellar media

Nucleophilicity of aromatic and aliphatic hydroxamate ions towards C=O and P=O center in cationic micellar media

ChemInform Abstract: From α‐Nucleophiles to Functionalized Aggregates: Exploring the Reactivity of Hydroxamate Ion Towards Esterolytic Reactions in Micelles

AbstractReview: [98 refs.

From α-nucleophiles to functionalized aggregates: exploring the reactivity of hydroxamate ion towards esterolytic reactions in micelles.

Owing to the rising threats of neurotoxic organophosphosphorus compounds, facile and efficient decontamination systems are required. Since the last few decades, the search for promising α-nucleophiles for straightforward and eco-friendly decontamination reactions using α-nucleophiles has been considerably boosted up. Among these, hydroxamic acids have been widely studied due to their potential α-nucleophilicity towards carbon and phosphorus based esters. This account summarizes our research on α-nucleophilicity of hydroxamate ions in water and micelles towards esterolytic reactions. Efforts of our group in the last few years have been collectively judged and compared with the crucial findings of researchers in the relevant field. The present article sheds light on the rich chemistry of the hydroxamate ion as a perfect candidate to degrade organophosphorus esters (i.e. nerve agents, pesticides and their simulants) in water, in micelles of conventional surfactants, and in functionalized micelles. The current report also provides an insight into the possible nature and mechanisms of these reactions. A brief account of the biological activities of hydroxamic acids that have recently spurred research in medicine against some fatal diseases has been included.

O‐Nucleophilicity of Hydroxamate Ions for Cleavage of Carboxylate and Phosphate Esters in Cationic Micelles

ABSTRACTThe nucleophilic reactivities of hydroxamate (HA−) ions of the structure RCONHO− [R = CH3 (acetohydroxamate, AHA−), C6H5 (benzohydroxamate, BHA−), 2‐OHC6H4 (salicylhydroxamate, SHA−), and 4‐CH3OC6H4 (4‐methoxbenzohydroxamate, MBHA−)] for the hydrolysis of p‐nitrophenyl benzoate (PNPB), tris(3‐nitrophenyl) phosphate (TRIS), and bis(2,4‐dinitrophenyl) phosphate (BDNPP) have been examined kinetically. Over the pH range of 6.7–11.4, the α‐nucleophile (HA−) accelerates deacylation of PNPB and dephosphorylation of TRIS (in cetyltrimethylammonium bromide (CTAB) micelle, 2.0 × 10−3 M). The salicylhydroxamate ion encountered effective catalysis than AHA−, BHA−, and MBHA− ions. The monoanionic SHA− and dianionic SA2− forms of salicylhydroxamic acid are the reactive species. The hydroxamic acid concentration–dependent critical micelle concentration (cmc) and fractional ionization constant (α) and of CTAB provide qualitative information for the micellar incorporation of the hydroxamate ion. The ab initio calculations performed on the hydroxamate ions at restricted Hartree–Fock using the 6‐311G (d,p) basis set revealed the O‐nucleophilicity of hydroxamate ions toward C=O and P=O centers. On the basis of ab initio calculation, it has been concluded that hydroxamic acids can exist into E‐amide and Z‐amide forms. The large stable amide or imide anions of hydroxamate are strong nucleophilic for the esterolytic cleavage of carboxylate and phosphate esters.

Modelling Np(IV) Solvent Extraction between 30% Tri-Butyl Phosphate and Nitric Acid in the Presence of Simple Hydroxamic Acids

Formo- and aceto-hydroxamic acids are very effective reagents for stripping tetravalent actinide ions from a tri-butyl phosphate phase into nitric acid. A model describing the partitioning of actinide (IV) ions has been derived accounting for reactions in the aqueous and solvent phases, including complex formation with nitrate and hydroxamate ions. Predicted distribution ratios for Np(IV) are compared with experimental data in the presence of aceto-hydroxamate ions. Additionally, a value of 0.473 (±0.004) kgmol−1 for the Np(IV) ion interaction coefficient with nitrate ions (εNp4+-NO3−) was determined.

Nucleophilic Attack of Salicylhydroxamate Ion at C═O and P═O Centers in Cationic Micellar Media

The reaction between the salicylhydroxamate anion (SHA(-)) and p-nitrophenyl benzoate (PNPB), tris(3-nitrophenyl)phosphate (TRIS), and bis(2,4-dinitrophenyl)phosphate (BDNPP) have been examined kinetically. The α-nucleophile, SHA(-), incorporated into cetyltrimethylammonium bromide (CTAB) micelles accelerates dephosphorylation of tris(3-nitrophenyl)phosphate (TRIS) over the pH range 6.7-11.4. With a 1.0 mM of SHA in CTAB, the nucleophilicity of SHA followed the order of reactivity, PNPB (C=O, carboxylate ester) > TRIS (P=O, triester) > BDNPP (P=O, diester), and monoanionic SHA(-) and dianionic SA(2-) are the reactive species. The critical micelle concentration, cmc, of cetyltrimethylammonium bromide (CTAB) decreases and the fractional ionization constant, α, increases with increasing the concentration of SHA(-). Addition of 1 and 10 mM SHA under the reaction conditions (pH 9.2, borate buffer) led to saturation of the micellar surface and provided qualitative information for the micellar incorporation of hydroxamate ion. Plots of the pseudo-first-order rate constant, k(obs), log k(obs), fraction of hydroxamic acid ionized, α(SHA(-)) and α(SA(2-)), vs pH showed bifunctional nucleophilicity of hydroxamic acid under micellar condition. Plotting k(obs) vs [SHA](T) gave a straight line with intercept k(0). This indicates that hydroxamate ions are very strong nucleophiles for nucleophilic attack at the C and P center. The pseudo-first-order rate constant-surfactant profiles show micelle-assisted bimolecular reactions involving interfacial ion exchange between bulk aqueous media and micellar pseudophase.

Nucleophilic debenzoylation of p -nitrophenyl benzoate in cationic micellar media

Pseudo-first-order rate constants for the nucleophilic debenzoylation reaction of p-nitrophenyl benzoate with various hydroxamate ions [RC = ONHO−] were investigated in aqueous cationic micellar media at pH 7.8 and 27°C. The kinetic rate data of the reaction revealed that the nucleophilic reactivity sequence of these hydroxamate ions is generally benzohydroxamic acid > salicylhydroxamic acid > acetohydroxamic acid. The kobs value increases upon addition of cationic surfactants to the reaction medium involving interfacial ion exchange between bulk aqueous media and micellar pseudophase. The effect of surfactant head and tail group is discussed. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 106–112, 2010

The Mechanism of Dephosphorylation of Bis(2,4-dinitrophenyl) Phosphate in Mixed Micelles of Cationic Surfactants and Lauryl Hydroxamic Acid

Mixed micelles of cetyltrimethylammonium bromide (CTABr) or dodecyltrimethylammonium bromide (DTABr) and the alpha-nucleophile, lauryl hydroxamic acid (LHA) accelerate dephosphorylation of bis(2,4-dinitrophenyl)phosphate (BDNPP) over the pH range 4-10. With a 0.1 mole fraction of LHA in DTABr or CTABr, dephosphorylation of BDNPP is approximately 10(4)-fold faster than its spontaneous hydrolysis, and monoanionic LHA(-) is the reactive species. The results are consistent with a mechanism involving concurrent nucleophilic attack by hydroxamate ion (i) on the aromatic carbon, giving an intermediate that decomposes to undecylamine and 2,4-dinitrophenol, and (ii) at phosphorus, giving an unstable intermediate that undergoes a Lossen rearrangement yielding a series of derivatives including N,N-dialkylurea, undecylamine, undecyl isocyanate, and carbamyl hydroxamate.

Micellar Effects on Hydrolysis of Parathion

Kinetics of the reaction between a pesticide (Parathion) and α-nucleophile hydroxamate ion (N-methyl 4-chlorobenzohydroxamate ion and N-methyl 4-chlorothiobenzohydroxamate ion) have been studied in the presence of various novel cationic surfactants at 27°C. The reaction exhibits pseudo first order kinetics and the rate of hydrolysis increased with surfactant concentration.

Effect of PEG-4000 & PEG-8000 on the Reactivity of Hydroxamate Ion

The hydrolysis of the p-nitrophenyl acetate catalyzed by different hydroxamate ions (RCONHO−; R = C6H5, 2-OHC6H4, CH3) was investigated at 27°C in aqueous media containing polyethylene glycol(MW = 4000 and 8000) at various pH values. Hydroxamate ions are effective alpha effect nucleophile for acylation reactions. Addition of PEG accelerates the rate of hydrolysis. The rate-polymer profile has been explained by applying different models. A mechanism for the catalyzed reaction is proposed. The BHA-PEG combination is more effective.

Solvent effect on the α-effect for reaction of p-nitrophenyl diphenylphosphinate with N-methyl 4-methoxy benzohydroxamate ion

Second order rate constants have been measured spectrophotometrically for the reaction of p-nitrophenyl diphenylphosphinate with N-methyl 4-methoxy benzohydroxamate ion in dimethylsulfoxide–water and acetonitrile–water mixtures (10–70% v/v) at 27 °C. The reactivity of hydroxamate ion towards p-nitrophenyl diphenylphosphinate increase upon addition of dimethylsulfoxide where decrease upon addition of acetonitrile into the reaction medium up to 10% (v/v) and is followed by a gradual increase upon further additions. The reactivity of α-nucleophile hydroxamate ion has been compared with normal nucleophile p-chlorophenoxide ion. The kinetic results have been explained on the basis of p K a, α-nucleophile and differential solvent effect.

Solvent Extraction Behavior of Neptunium (IV) Ions between Nitric Acid and Diluted 30% Tri‐butyl Phosphate in the Presence of Simple Hydroxamic Acids

Formo‐ and aceto‐hydroxamic acids are very effective reagents for stripping tetravalent actinide ions such as Np(IV) and Pu(IV) ions from a tri‐butyl phosphate phase into nitric acid. Distribution data for Np(IV) in the presence of these hydroxamate ions have now been accumulated and trends established. Stability constants for aceto‐hydroxamate complexes of Np(IV) and Np(V) ions have also been determined in a perchlorate medium, and these reaffirm the affinity of hydroxamate ligands for actinide (IV) ions over actinyl (V,VI) ions.