Picrate Ion Research Articles

Charge Transfer and Proton Transfer in the Formation of Molecular Complexes. XII. o-Aminobenzoic Acid–Picric Acid and Related Complexes

Abstract The combination of o-aminobenzoic acid and picric acid was found to yield four kinds of adducts. These were a stable yellow (1:1) salt, formed by the proton transfer from the picric acid to the o-aminobenzoic acid molecule, two red (1:1) molecular complexes of markedly different stability, and a red (2:1) complex consisting of the o-aminobenzoic acid molecule, its protonated ion, and the picrate ion. The enthalpy change and the activation energy for the isomerization from the salt to the charge-transfer complex by a solid-solid transformation were shown to decrease during storage. The 1,3,5-trinitrobenzene complexes with o-(methylamino)benzoic acid, o-, m-, and p-(dimethylamino)benzoic acids, and their sodium and potassium salts were prepared. Their electronic spectra were measured, along with those of the complexes with o- and p-aminobenzoic acids and their salts presented in the work of Sudborough and Beard. The displacement of the charge-transfer absorption maxima to the lower wavenumber side by the salt formation is 2×103 cm−1 on the average and seems to be consistent with our proposition that the picrate ion acts as an electron acceptor in aromatic amine-picric acid (2:1) complexes.

Charge transfer between two immiscible electrolyte solutions Part VI. Polarographic and voltammetric study of picrate ion transfer across the water/nitrobenzene interface

Charge transfer between two immiscible electrolyte solutions Part VI. Polarographic and voltammetric study of picrate ion transfer across the water/nitrobenzene interface

Charge transfer between two immiscible electrolyte solutions: Part VI. Polarographic and voltammetric study of picrate ion transfer across the water/nitrobenzene interface

The transfer of the picrate ion across the interface between two immiscible electrolyte solutions, 0.05 M LiCl in water and 0.05 M tetrabutylammonium tetraphenylborate in nitrobenzene was investigated by electrolysis with the electrolyte dropping electrode and by cyclic voltammetry. Under the conditions of the experiments the charge-transfer process is controlled solely by diffusion. The maximum which appears on the polarogram of the picrate ion close to the limiting current can be suppressed by the addition of a surface-active substance (gelatine). The diffusion coefficients of the picrate ion in the aqueous and nitrobenzene phase were determined from the limiting polarographic current and from the peak current on the cyclic voltammogram. The value of the formal potential of the charge-transfer reaction, which was calculated from the half-wave potential or from the peak potential, is in good agreement with that inferred from the extraction data.

Transfer activity coefficients of alkali, silver, thallium(I), chloride, and picrate ions between methanol and propylene carbonate

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTransfer activity coefficients of alkali, silver, thallium(I), chloride, and picrate ions between methanol and propylene carbonateM. K. Chantooni Jr. and I. M. KolthoffCite this: J. Chem. Eng. Data 1980, 25, 3, 208–211Publication Date (Print):July 1, 1980Publication History Published online1 May 2002Published inissue 1 July 1980https://doi.org/10.1021/je60086a022RIGHTS & PERMISSIONSArticle Views65Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (474 KB) Get e-Alerts Get e-Alerts

Titrimetric determination of iodide, hexacyanoferrate(ii), thiourea, cationic surfactants, and of picrate with a picrate ion-selective electrode

Methods have been developed for the semiautomatic potentiometric precipitation titration of iodide, hexacyanoferrate(II), sulfide, and sulfide-thiourea mixtures with silver nitrate, of medically important quaternary ammonium compounds with sodium picrate, and of picrate ions with tetraphenylarsonium chloride, using a picrate ion-selective electrode. Semimicro and/or microamounts of these substances were determined with relative errors and relative standard deviations of 1–2%.

The effect of binding ions on the oxidation of horse heart ferrocytochrome c

The effect of various specific binding ions on the rate of oxidation by potassium ferricyanide of electrodialyzed horse heart ferroeytochrome c was studied. The ionic strength was kept constant using Tris–cacodylate buffer, pH 7.0. Either the Tris or cacodylate ion was replaced by the binding ion studied. At an ionic strength of 0.194 M (24 °C), replacing cacodylate by chloride decreased the bimolecular oxidation rate constant from about 13.3 × 106 (Tris–cacodylate) to about 8.8 × 106 M−1 s−1 (Tris–chloride). Comparable decreases were found when cacodylate was replaced by phosphate or when Tris was replaced by potassium. When picrate replaced cacodylate (ionic strength 0.0485 M) a larger decrease was found, from about 5.2 × 107 to about 0.8 × 107 M−1 s−1. Data at intermediate ion concentrations were consistent with a simple cooperative binding model. The calculated association constants for chloride, potassium, and phosphate were in the range of 2–20 M−1, while for picrate it was 500 M−1. The data were consistent with one bound ion per ferroeytochrome c molecule, except for picrate, for which two binding sites were suggested. The results were interpreted by the hypothesis that the picrate ion binds near the solvent-exposed heme edge. The electron transfer reaction of ferricyanide was also presumed to take place through this region. The other ions probably bind at some distance from the heme edge and were suggested to exert their effect by perturbing the proteins' solvent shell. Consistent with this was the effect of replacing H2O by D2O which decreased the oxidation rate constant by about 50%.

Transfer free energies of some ions from water to dimethylsulfoxide-water and urea-water mixtures

The standard free energies of transfer (ΔGto) of some electrolytes from water to aqueous mixtures of dimethylsulfoxide (DMSO) and of urea have been split into the contribution from individual ions by use of the reference electrolyte Ph4AsBPh4 (RE), where Ph=phenyl. For each of the solvents, ΔGto(Ph4AsBPh4) was determined from the solubility products of the salts KBPh4, Ph4AsPi, and KPi, where Pi=picrate ion. The observed ΔGto(i) values for the individual ions are strikingly different from the corresponding values obtained by the simultaneous extrapolation (SE) procedure reported earlier.

Solvent extraction of lead(II) and strontium(II) as dibenzo-18-crown-6 complexes with picrate ion

The solvent extraction of lead(II) and strontium(II) from aqueous lithium picrate solutions with dibenzo-18-crown-6 (DBC) in chloroform or benzene has been measured. From slope analysis, the extracted species are found to be Pb(DBC)(Pic) 2 and Sr(DBC)(Pic) 2. The distribution ratio of lead(II) is about forty to fifty times that of strontium(II). This is ascribed to the higher stability of the lead(II) DBC complex, and to weaker hydration of the lead(II) DBC complex. The extraction of both metals is stronger into a benzene than into a chloroform solution of DBC.

Extraction based on the flow-injection principle: Part 2. Determination of codeine as the picrate ion-pair in acetylsalicylic acid tablets

Codeine in aqueous samples is extracted as its picrate ion pair into chloroform in a continuous flow system. The sample is introduced into an aqueous picrate stream buffered at pH 6.5 ; its dispersion gives controlled mixing before the aqueous stream is segmented by a chloroform stream. A specially constructed fitting is included to produce segments, typically 5–10 mm long, which pass into a Teflon coil (2 m long; inner diameter, 0-8 mm). At the outlet of the coil. the phases are separated and a fraction of the chloroform phase is passed through a spectrophotometric flow cell. The sample volume is in the range 25–40 μl, the sampling rate about 60 h , and the relative standard deviation of the order of 1%.

Dissociation kinetics of picric acid and dipicrylamine in methanol. Steric effect on a proton transfer rate

The acid–base dissociation kinetics of picric acid and 2,2′,4,4′,6,6′-hexanitrodiphenylamine(I) in methanol at 25°C have been investigated using the electric field jump method. The rate constants for the reaction [graphic omitted], where HA denotes picric acid, are k1= 4.3 × 1010 dm3 mol–1 s–1 and k–1= 9.2 × 106 s–1. For (I) the corresponding values are k1= 2.28 × 109 dm3 mol–1 s–1 and k–1= 1.31 × 105 s–1. The dissociation constant of (I) in methanol was determined to be K= 5.4 × 10–5 in agreement with the value derived from the kinetics. The protonation rate constant k1 of the picrate ion indicates a diffusion controlled reaction. It is suggested that the surprisingly small value of k1 for the protonation of the anion of (I) can be ascribed to steric shielding of the acidic nitrogen atom by the adjacent nitro groups in this compound.

Optical Spectra of the Picrate Ion in Micellar and Polymer Micellar Systems. Comment on the Solvation of Anions

Abstract The optical spectra of the picrate ion in a micellar solution indicate that slightly below the CMC of CTAB surfactant the anion is relatively free and exists as an ion pair above the CMC. The hydrophobic aggregate of TMAC invariably gives free ion. The polymer micelle of quaternized poly(4-vinylpyridine) results in a tight ion pair.

The Solvent Extraction of Thallium(I) as a Dibenzo-18-crown-6 Complex with the Picrate Ion

Abstract The solvent extraction of thallium(I) with dibenzo-18-crown-6 (DBC) as the picrate into chloroform and benzene was measured at 25 °C. The extraction was nearly the same as that of potassium(I) and much better than rubidium(I); this tendency was mainly attributed to the difference in the stability of the DBC complexes in the aqueous phase. Thallium(III) was extracted only poorly.

High-performance ion-pair liquid chromatography: Application to dissolution rate and content uniformity testing of pharmaceuticals

Summary Schill and his group have shown that ion partners with good chromophores can be used to improve detection properties following separation of picrate ion pairs on cellulose columns. We have shown recently that the same concept can be transferred to high-performance liquid chromatographic conditions using small particle silica gel. In this work these systems were investigated to further substantiate some of the claims previously made concerning the predictability of chromatographic data and the application of these systems. Good correlations were found between capacity factors calculated from batch experiments and chromatographically determined data. In the course of this study the influence of temperature, pH and concentrations of picric acid [X − ] on E QX and on retention data ( k ′, a ) were studied. Trinitrobenzenesulfonic acid (TNBS) was tried as a substitute for picric acid due to its better solubility properties. It was found that the picric acid continuously formed in the trinitrobenzenesulfonic acid-stationary phase and not the TNBS is responsible for ion pair formation. The applications work revealed up to a fiftyfold enhancement in detection limits for several tropa alkaloids in comparison to reversed-phase chromatography (detection at 215 nm). In addition large concentrations of non-complexing compounds can be suppressed by using the picric acid absorption maximum at 345 nm. The method has been applied to content uniformity studies and dissolution rate testing of tablets. The reproducibility of these operations were always below 2% rel. S.D.

Transfer rate of K + ions from aqueous picrate solutions into 1,2 dichloroethane solutions of the macrocyclic polyether dibenzo-18-crown-6

The transfer rate of K + ions from aqueous picrate solutions into 1,2 dichloroethane solutions of the macrocyclic polyether dibenzo-18-crown-6, DBC, has been studied by potassium glass electrode potentiometry using a constant interfacial area cell, at 25°. The rate at time zero has been evaluated as function of the following variables: stirring speed of the phases, interfacial area, volume of aqueous and organic phase, chemical composition. The data have shown that the rate of extraction of potassium can be explained in terms of chemical reactions taking place at the water-organic interphase. The reaction order with respect to both K + and picrate ions has been found equal to one. The reaction order with respect to DBC was found to vary with the DBC concentration from an initial value of one down to zero.

The stabilities of Meisenheimer complexes. Part 15. The interactions of 2,4,6-trinitrobenzenesulphonate ions with sodium sulphite and with sodium hydroxide in water

In the presence of aqueous sodium sulphite 2,4,6-trinitrobenzenesulphonate ions give 1 : 1 and 1 : 2 adducts by sulphite addition at unsubstituted ring positions; kinetic and equilibrium data are reported. It is shown that the initial fast reaction of 2,4,6-trinitrobenzenesulphonate ions with aqueous sodium hydroxide results in hydroxide attack at the unsubstituted 3-position, and that ionisation of the added hydroxy-group occurs. The slower addition of hydroxide at the 1-position leads to nucleophilic substitution giving picrate ions and the observation of base catalysis in this reaction is discussed.

Titrimetric determination of thiourea and silver with a picrate ion selective electrode

A method has been developed for the semiautomatic potentiometric titration of thiourea with silver nitrate and of silver with thiourea, in the presence of picrate ions, using a picrate ion selective electrode. Thiourea in the range 15–1500μg and silver in the range 200–1800μg were determined with relative errors and relative standard deviation of about 1%.

Copper(II) acetate and picrate complexes of sulfa drugs

Copper(II) acetate and picrate complexes of sulfa drugsviz., sulfanilamide, sulfaguanidine, sulfathiazole, sulfadiazine, sulfamerazine and sulfamethazine were prepared and characterized with the help of analytical, electronic, i.r. and magnetic moment data. The complexes are paramagnetic, planar or mixed planar and octahedral, insoluble and melt (with decomposition) in the 185°–225° range. The sulfa drugs coordinate through their amino groups and the acetate or picrate ions are bonded to the metal through the -C(O)O group.

Specific interactions including imidazolium andN-methylimidazolium lons. I. Interactions with the picrate anion

The conductances of solutions of methylimidazolium and imidazolium picrate (MeImHPic and ImHPic) in nitrobenzene-benzene mixtures (27.2<D<34.8) have been measured in order to study their ionic association. The conductance data for MeImHPic indicate only ion pair association. Deviations occur in the case of ImHPic in that the apparent ion pair association constant decreases with an increase in the salt concentration, which is interpreted as due to formation of triple ions of the type PicImHPic−. These triple ions are highly stabilized by the hydrogen bond between the second NH group of the ion pair and the second picrate ion. Values of the formation constants for the ion pair ImHPic and for the triple ion PicImHPic− have been calculated and are discussed.

Field dissociation effect, chemical relaxation, and conductance of tetrabutylammonium picrate ion pairs in diphenyl ether

Field dissociation effect, chemical relaxation, and conductance of tetrabutylammonium picrate ion pairs in diphenyl ether

The stabilities of Meisenheimer complexes. Part XIII. Kinetic and equilibrium data for spiro-complex formation from 1-(2-mercaptoethylthio)- and 1-(2-hydroxyethylthio)-2,4,6-trinitrobenzene in water

Cyclisation of 1-(2-mercaptoethylthio)-2,4,6-trinitrobenzene occurs in water to give a spiro complex (III), of high thermodynamic stability. Opening of the dithiolan ring of (III) is catalysed by mercury(II) ions but not by acids. In the presence of aqueous base cyclisation of 1-(2-hydroxyethylthio)-2,4,6-trinitrobenzene to the spiro complex (IV) is followed by irreversible decomposition to ethylene sulphide and picrate ions. Kinetic and equilibrium data for the formation of (III) and (IV) are reported and are compared with those for the analogous dioxolan, complex (V).