The use of sulfamic acid as a primary standard in nonaqueous titrimetry

A method has been developed for the standardization of a typical nonaqueous base lithium methoxide, with an inorganic primary standard, sulfamic acid. 'T'his acid was found to dissolve readily in four independant basic solvents, dimethyl formamide, ethylenediamine, n-butylamine and dimethyl sulfoxide. Sulfamic acid could be titrated in each of these solvents, by both visual and potentiometric means with lithium methoxide dissolved in benzene-methanol. No gels nor precipitates resulted in the course of the titrations and the accuracy of the method was comparable to that obtained using benzoic acid as the primary standard. Conductometric titrations were also performed using sulfamic acid dissolved in two systems, dimethyl formamide and glacial acetic acid. In the latter solvent it was possible to titrate sulfamic acid with perchloric acid in glacial acetic acid.     

Molecular recognition of l-leucyl-l-alanine: enantioselective inclusion of alkyl methyl sulfoxides

A simple aliphatic dipeptide, l-leucyl-l-alanine (Leu-Ala), includes several alkyl methyl sulfoxides enantioselectively to form inclusion crystals. From single-crystal X-ray analyses of three inclusion compounds of dimethyl sulfoxide (DMSO), isobutyl methyl sulfoxide, and benzyl methyl sulfoxide, it was elucidated that Leu-Ala molecules self-assemble to form layer structures and the sulfoxides are included via hydrogen bonding in a cavity between these layers. The inclusion cavity has methyl group and isobutyl group at its each side, and the guest sulfoxide is placed in such a manner that its methyl group faces toward the methyl of the Leu-Ala cavity. When the alkyl group of the sulfoxide is comparably large, it is located in the residual space of the cavity to attain effective crystal packing. Thus, the sulfoxides having a comparably large group such as isobutyl, butyl, and benzyl are included with a high (R)-enantioselectivity in Leu-Ala crystals.     

Sodium hydride-initiated polymerizations of vinyl monomers in aprotic solvents

Polymerizations of several vinyl monomers at 25°C in aprotic solvents (dimethyl sulfoxide, N,N-dimethylacetamide, and hexamethylphosphoric triamide) using sodium hydride dispersion as initiator yield low to intermediate molecular weight polymers. The molecular weight of the resulting polymer as well as the mode of initiation depends on the monomer and aprotic solvent used. Initiation of polymerization of monomers with available α hydrogens (methyl acrylate, acrylonitrile) involves monomer anion, while initiation of a monomer with no α hydrogen (methyl methacrylate) proceeds by a more complex mechanism. In contrast, initiation of styrene and α-methylstyrene proceeds by dimsyl anion addition to monomer in dimethylsulfoxide. Although the triad tacticities and number-average molecular weights of poly(methyl methacrylate) samples obtained from all three aprotic solvents are nearly the same, poly(methyl methacrylates) prepared in dimethyl sulfoxide and N,N-dimethylacetamide give polymers having polydispersities of ～3, while a very polydisperse polymer is obtained in hexamethylphosphoric triamide.     

Investigation of phase equilibria of levulinic acid distribution between aqueous phase to organic phase by Aliquat 336 in different modifiers

The extraction of levulinic acid by tricaprylmethylammonium chloride (Aliquat 336) dissolved in five alcohols solvents (isoamyl alcohol, hexan-1-ol, octan-1-ol, nonan-1-ol, decan-1-ol) and five esters solvents (dimethyl phthalate, dimethyl adipate, dimethyl succinate, dimethyl glutarate, diethyl carbonate), two ketones (diisobutyl ketone (DIBK), methyl isobutyl ketone (MIBK)) were investigated to understand effect of modifier on levulinic acid extraction. In addition to these Aliquat 336 + modifier system, the experiments were done also with single solvents. All measurements were carried out T = 298.15 K. Organic solutions of Aliquat 336 are being used increasingly to separate organic acids from aqueous mixture solutions by reactive extraction. The extent to which the organic phase may be loaded with levulinic acid is explained as a loading ratio, Z_Z, extraction efficiency E and, distribution coefficients K_D were calculated. The maximum extraction efficiency was obtained value of 72.1 for isoamyl alcohol. The extraction equilibrium constant, K_E, has been calculated for each modifier. Furthermore, Freundlich, Langmuir, and LSER model equations have been obtained for experimental data of alcohols.     

Features of autoxidation of ferrocenylcarboxylic acid and its methyl ester in organic solvents in the presence of Brønsted acids

We have studied the autoxidation of ferrocenecarboxylic acid and its methyl ester in organic solvents in the presence of perchloric and trifluoroacetic acids. Based on the results of kinetic studies and data on the composition of the reaction products, we suggested the possible reaction mechanisms, including those of molecular and radical-chain macrostages of the process. The features of the solvent influence on the rate of oxidation of metallocomplexes and the reasons for its extreme dependence with increasing concentration of perchloric acid are discussed.     

Preparation of 9, 9-dimethylfluorene in methylphosphonic acid tetramethyldiamide and other cation-solvating solvents

Conclusions 9, 9-Dimethylfluorene was obtained in high yield (95%) upon metallation of fluorene with potassium tert-butoxide with subsequent treatment of the reaction mixture with methyl iodide in cation-solvating solvents: methylphosphonic acid tetramethyldiamide, hexamethapol, dimethyl sulfoxide, diglyme.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 182–183, January, 1969.     

Capillary electrophoresis of boron cluster compounds in aqueous and nonaqueous solvents

The electrophoretic properties of boron cluster compounds were determined in water, methanol and ACN as solvents of the BGE and discussed based on the principles of ion migration. Two types of boron cluster compounds were investigated. One type consisted of derivatives of the nido-7,8-dicarbaundecaborate cluster, the other types are derivatized cobalt bis(dicarbollide) ions (COSANs) whose central cobalt atom is sandwiched by two 7,8-dicarbaundecaborate clusters. The BGE in all solvents was acetate/acetic acid buffer with pH 4.75 in water, 9.7 in methanol and 22.3 in ACN, respectively, at different ionic strength between 5 and 30 mM. The dependence of the mobility on ionic strength could not be explained by the theory of Debye, Hückel and Onsager, but good agreement was found upon considering an ion size parameter. Limiting mobilities were derived by curve fitting, and by the aid of the solvent viscosities the hydrodynamic radii of the analyte anions were calculated. They are between 0.25 and 0.48 nm, and were nearly independent of the solvent. Electrophoresis of the analytes in a BGE consisting of 6 mM perchloric acid in ACN allows the conclusion that the present boron cluster compounds behave as stronger acids than perchloric acid.     

Acid-base titrations in nonaqueous solvents Analysis of dimethyl sulphate

A nonaqueous titrimetric procedure was developed for the determination of the dimethyl sulphate, methyl hydrogen sulphate and sulphuric acid content of dimethyl sulphate samples. Methyl hydrogen sulphate and sulphuric acid are determined by a differentiating potentiometric titration in pyridine with tributylethylammonium hydroxide. Pyridine converts the dimethyl sulphate into the weakly acidic methylpyridinium methyl sulphate which does not interfere in the titration. Dimethyl sulphate is determined by reacting it with an excess of 2-dimethylaminoethanol and titrating the excess with perchloric acid. Precision and recovery data for commercial samples of dimethyl sulphate are presented.     

On the influence of some strong electrolytes on the partitioning of acetic acid to aqueous/organic two-phase systems in the presence of tri-n-octylamine: Part II: Toluene as organic solvent

Water-insoluble amines (dissolved in an organic solvent/organic solvent mixture) are often used for the extractive recovery of carboxylic acids from aqueous phases. The basic design of the extraction process requires a thermodynamic framework that should be able to describe the liquid–liquid phase equilibrium not only in the phase forming systems (water + carboxylic acid + organic solvent + reactive extractant), but also when the aqueous feed phase contains additionally small amounts of strong electrolytes. Even small amounts of strong electrolytes might considerably reduce the recovery rate. In part I of this series such a model was presented and discussed for methyl isobutyl ketone as organic solvent and tri-n-octylamine (TnOA) as the chemical extractant. The present part II is to demonstrate that the procedures/methods described for methyl isobutyl ketone as organic solvent can be applied also for other organic solvents. By way of example, here toluene is that organic solvent. New experimental results are reported for the influence of sodium chloride, sodium nitrate, sodium sulfate, sodium acetate and hydrochloric acid on the partitioning of acetic acid to coexisting aqueous/organic liquid phases of the system (water + toluene + tri-n-octylamine) at 25 °C. An extension/adaptation of the previously published thermodynamic framework is successfully applied to describe/predict the new experimental liquid–liquid phase equilibrium data.     

Studies on the extraction and determination of metal salts with isobutyl methyl ketone-XIV Extraction of gold

The isobutyl methyl ketone extraction of gold(III) from hydrochloric acid or various mixtures of hydrochloric and other mineral acids was studied as a function of the gold concentration and the acid concentration. Gold (initial concentration up to 5 x 10(-3)M) was quantitatively extracted (99%) from 3-5M hydrochloric acid. Addition of nitric acid in 1-5M concentration and sulphuric or perchloric acid in 1-3N concentration to the 1-5M hydrochloric acid solutions used had no effect.     

Novel chiral poly(ester-imide)s with different natural amino acids in the main chain as well as in the side chain: synthesis and characterization

Several novel chiral and potentially biodegradable poly(ester-imide)s (PEI)s bearing natural amino acids in the main chain as well as in the side chain were synthesized via direct polyesterification of N,N'-(pyromellitoyl)-bis-(L-tyrosine dimethyl ester) as a biodegradable optically active phenolic diol and synthesized diacids containing different amino acids and phthalimide group in the side chain. With the aim of tosyl chloride/pyridine/N,N-dimethylformamide (DMF) system as a condensing agent under conventional heating condition, the new optically active PEIs were obtained in good yield and moderate inherent viscosity up to 0.35 dL/g. The obtained polymers were characterized with FT-IR, ¹H NMR, X-ray diffraction (XRD), elemental and thermogravimetric analysis (TGA) techniques. They are readily soluble in amide type solvents such as N,N-dimethylacetamide, DMF, 1-methyl-2-pyrrolidone, dimethyl sulfoxide, and protic solvents such as sulfuric acid. TGA showed that the 10% weight loss temperature in argon atmosphere was around 350 °C, which indicates that the resulting PEIs have a good thermal stability. The presence of amino acid in the PEIs architecture, not only cause to be used as optically active materials but also makes them susceptible to be biocompatible and biodegradable compound.     

Starch Formates: Synthesis and Modification

Starch can be efficiently converted into the corresponding formates homogeneously using N-formyl imidazole obtained by the reaction of 1,1′-carbonyldiimidazole and formic acid in dimethyl sulfoxide as a solvent. Starch formates are soluble in polar aprotic solvents, not susceptible against hydrolysis, and not meltable. Thermoplastics could be generated by conversion of starch formates with long-chain fatty acids exemplified by the conversion with lauroyl chloride in N,N-dimethylacetamide, leading to mixed starch laurate formates. The mixed esters show melting temperatures mainly dependent on the amount of laurate ester moieties.     

Extraction of aqueous of malic acid by trioctylamine extractant in various diluents

In this study malic acid were extracted from aqueous solution by different solvents with and without trioctylamine (TOA). The TOA was dissolved in five different esters (dimethyl phthalate, dimethyl adipate, dimethyl succinate, dimethyl glutarate, and diethyl carbonate), five different alcohols (isoamyl alcohol, hexan-1-ol, octan-1-ol, nonan-1-ol, and decan-1-ol) and two different ketones (diisobutyl ketone (DIBK) and methyl isobutyl ketone (MIBK)). The results are reported as distribution coefficients (K_D), loading factors (T_T), stoichiometric loading factor (T_S), separation factor (S_f) and extraction efficiency (E). The most effective solvent was determined as isoamyl alcohol with a distribution value coefficient of 17.811. The maximum values of equilibrium complexation constants in isoamyl alcohol for (acid:amine) (1:1) K₁₁ and (2:1) K₂₁ were 9.9 and 225.6, respectively. A linear solvation energy relationship (LSER) was accurately regressed to the experimental distribution coefficients.     

Quantification of residual solvents in antibody drug conjugates using gas chromatography

The detection and quantification of residual solvents present in clinical and commercial pharmaceutical products is necessary from both patient safety and regulatory perspectives. Head-space gas chromatography is routinely used for quantitation of residual solvents for small molecule APIs produced through synthetic processes; however residual solvent analysis is generally not needed for protein based pharmaceuticals produced through cultured cell lines where solvents are not introduced. In contrast, antibody drug conjugates and other protein conjugates where a drug or other molecule is covalently bound to a protein typically use solvents such as N,N-dimethylacetamide (DMA), N,N?dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or propylene glycol (PG) to dissolve the hydrophobic small molecule drug for conjugation to the protein. The levels of the solvent remaining following the conjugation step are therefore important to patient safety as these parental drug products are introduced directly into the patients bloodstream. We have developed a rapid sample preparation followed by a gas chromatography separation for the detection and quantification of several solvents typically used in these conjugation reactions. This generic method has been validated and can be easily implemented for use in quality control testing for clinical or commercial bioconjugated products.     

The recovery of gallic acid with triphenylphosphine oxide in different kind of solvents

In this study, gallic acid was separated by triphenylphosphine oxide in the presence of conventional solvents. Triphenylphosphine oxide is an organophosphorus extractant and highly selective towards carboxylic acids. Reactive extraction results were compared with physical extraction results. The extraction efficiencies reached up to 61, 76, 86, 67, and 84% in the presence of triphenylphosphine oxide with oleyl alcohol, dimethyl adipate, isobutanol, methyl isopropyl ketone, and methyl ethyl ketone, respectively. Further, the number of theoretical units and the solvent to feed ratio were calculated for the practical design of a liquid-liquid extraction column. Roughly 2 to 4 theoretical units were calculated to meet the targeted extraction efficiencies. This study is the first to investigate the reactive extraction of gallic acid by triphenylphosphine oxide, and include fundamental information for the recovery of gallic acid.     

Occupational exposure to low levels of organic and inorganic substances in a chemical plant for the production of terephtalic acid dimethyl ester

The aim of our study was the evaluation of personal exposure to chemical pollutants in workers employed in a plant for the production of terephtalic acid dimethyl ester. Chemical agents have been included in the monitoring program on the basis of the industrial process. In the plant, the oxidation of p-xylene is performed by air and the resulting acid is esterified with methyl alcohol. Purified terephtalic acid dimethyl ester is then utilized for the production of polyethylene terephtalate. The environmental monitoring included terephtalic acid dimethyl ester, p-toluic acid methyl ester, terephtalic acid, p-xylene, methylacetate, methylbenzoate, formic acid, acetic acid, methanol, and the catalysts cobalt acetate and manganese (II) acetate tetrahydrate. Personal exposure to the cited airborne substances was performed in the breathing zone of six workers. Air samplings were carried out by drawing air through glass fibre filters (terephtalic acid dimethyl ester, p-toluic acid methyl ester and terephtalic acid aerosols), by active adsorption (methanol, formic and acetic acids vapours). p-Xylene, methylacetate and methylbenzoate vapours were collected by passive sampling. Cellulose nitrate filters were used for cobalt and manganese salts samplings. Analyses were performed by UV detection high-performance liquid chromatography (terephtalic acid dimethyl ester, p-toluic acid methyl ester and terephtalic acid), flame ionization detection gas chromatography (p-xylene, acetic acid methyl ester and benzoic acid methyl ester), ion chromatography (formic and acetic acids) and inductively coupled plasma-mass spectrometry (cobalt and manganese). The results were evaluated according to the threshold limit values (TLVs) of the American Conference of Governmental Industrial Hygienists (ACGIH) and indicated that the environmental levels of the workplace pollutants were well below the threshold limit values-time weighed average (TLV-TWA) adopted by the American Conference of Governmental Industrial Hygienists for 2002, although for three substances the TLVs were not available.     

Synthesis, optical, and thermal properties of conjugated, bispyridyl and tetrapyridyl compounds by Knoevenagel reaction

A series of conjugated, bispyridyl and tetrapyridyl compounds were synthesized from either terephthalaldehyde or isophthalaldehyde and activated pyridyl compounds by Knoevenagel reaction on heating in acetic anhydride in presence of acetic acid and their optical and thermal properties were examined. All of them exhibited photoluminescence in chloroform, tetrahydrofuran, and dimethyl sulfoxide as well as in solid state. In solid state, their emission spectra exhibited bathochromic shifts when compared with those in less or more polar solvents. Some compounds emitted UV light both in polar solvents and in the solid state; other compounds emitted UV light in polar solvents, but emitted visible light in the solid state.     

Preparation of no-carrier added 16-131I-hexadecanoic acid via halogen exchange: Comparison between two methods

A simple method for labelling of 16-Br-hexadecanoic acid (16-BrHDA) with radioactive iodine has been reported via nucleophilic¹³¹I-for-Br exchange in the dry state and in organic solvents. While preparation in some organic solvents such as acetic acid, dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) required reaction times of more than 2 hours to give yields of 20–50%, halogen exchange in dry state at temperature of about 100 °C gave rise to yields of about 94% of radiochemically pure 16-¹³¹IHDA within 5 min. The labelling product could be purified by high performance liquid chromatography (HPLC) and was shown to be free of significant radiochemical impurities.     

Crystallization of Pseudopolymorphs of Some Gamboge Pigments. Pyridine,Dimethylformamide and Dimethylsulfoxide Solvates of Morellic Acid,Gambogic Acid and Guttiferic Acid

Abstract

Morellic acid, gambogic acid and guttiferic acid are related naturally-occurring xanthone pigments that yield X-ray quality crystals only from solvents like pyridine, dimethylformamide (dmf) and dimethyl sulfoxide (dmso). The structures of four of these crystals have been determined and are found to contain solvents of crystallization. The solvents hydrogen bond to the carboxyl groups with O—H…O/N motifs previously seen in other carboxylic acids. Distinctive, however, is the presence of an extended though somewhat diffuse array of C—H…O hydrogen bonds that aggregates the entire solute-solvent assemblage in a multi-point manner. Pyridine and dmf are able to mimic each other with respect to their hydrogen bond donating and accepting characteristics and in this respect play equivalent roles in their solvates with morellic acid and gambogic acid. Dmso is seen to self-associate in its guttiferic acid solvate. It is possible that these solvents with multiple hydrogen bonding donor and acceptor capability can act as hydrogen bond nucleators, providing just enough rigidity to the solutes to ensure crystallization.     

Basicity comparison for di-substituted 4-nitropyridine derivatives in polar non-aqueous media

Acid dissociation, as well as cationic homoconjugation equilibria have been studied potentiometrically in systems involving four di-substituted 4-nitropyridines and conjugate cationic acids in the polar non-aqueous solvents - aprotic protophobic acetonitrile (AN) and propylene carbonate (PC), the amphiprotic methanol (MeOH), and in the aprotic protophilic dimethyl sulfoxide (DMSO). The influence of solvent effect on the obtained acidity constants has been discussed. The acidity constants (expressed as pK_a values) were compared with those previously determined in another polar protophobic aprotic solvent - acetone (AC), and obtained for the unsubstituted pyridine (Py). A comparison of the acid dissociation constants determined in all media studied has proved that the strength of the cationic acids increases on going from acetonitrile through propylene carbonate, acetone, and methanol to dimethyl sulfoxide. Furthermore, the values of acidity constants in the non-aqueous media have shown that in all the solvents studied they change according to the substituent effects. It has been also found that substituted 4-nitropyridine derivatives studied exhibit no tendency towards cationic homoconjugation in acetonitrile, propylene carbonate, and methanol and dimethyl sulfoxide. Moreover, it has been demonstrated that the acid dissociation constants determined by potentiometric titration method in all the solutions investigated correlate well with the calculated energy parameters of the protonation reactions in the gaseous phase.