Dilute Aqueous Acid Solutions Research Articles

Intramolecular nucleophilic cyclization of a carboxylic acid hydrazide under mild acid conditions

AbstractPhthaloyl‐2′‐nitrophenylhydrazide undergoes ring closure involving nucleophilic attack of the hydrazide on the carboxylic acid in dilute aqueous acid solution to form the corresponding N‐substituted phthalimide. Structure of the resulting phthalimide was unequivocally confirmed by 13C‐nmr.

Predictability of Reverse Osmosis Separations of Partially Dissociated Organic Acids in Dilute Aqueous Solutions

Predictability of Reverse Osmosis Separations of Partially Dissociated Organic Acids in Dilute Aqueous Solutions

Denitrosation of N-methyl-N-nitrosotoluene-p-sulphonamide in acid solution

N-Methyl-N-nitrosotoluene-p-sulphonamide (MNTS) undergoes quantitative denitrosation in dilute aqueous acid solution, to give N-methyltoluene-p-sulphonamide (MTS) and nitrous acid. The reaction is first order both in MNTS and acid, and zero order in added chloride, bromide, and thiourea. The rate of reaction is unaffected by the addition of nitrous acid traps such as sulphamic acid, and is also unchanged by the addition of MTS. From rate measurements in D4SO4–D2O, the kinetic isotope effect kH : kD was found to be 1.5. General acid catalysis was observed for dichloroacetic acid reactions. The observations are best fitted to a mechanism in which the proton transfer from the solvent to the reactant MNTS is rate limiting. Loss of NO+ from the conjugate acid occurs either unimolecularly or by reaction with a nucleophile (such as bromide ion) : it is not possible to distinguish between these alternatives. The results are very similar to those obtained for the denitrosation pathway of N-nitroso-amides, and contrast with those found for the denitrosation of N-nitroso-amines, where the protonation is fast, and nucleophilic catalysis is observed. The dominating effect in the present work appears to be the strong electron-withdrawing effect of the SO2 group.

The polymerization of acrylic acid in the presence of copolymers containing interacting and non-interacting groups

There has been a kinetic examination of the polymerization of acrylic acid in dilute aqueous solution in the presence of copolymers of vinyl pyrrolidone with acrylamide or styrene. In general, the characteristics of the polymerizations are very similar to those found in the presence of polyvinyl pyrrolidone homopolymer, but the definite differences, taken in conjunction with gravimetric data on the polymer complexes, can be explained by the fact that acrylamide is hydrophilic while styrene is hydrophobic. The use of the copolymers has permitted an assessment of the effect of dilution of monomer adsorbed on the interacting polymer.

Radiation-Induced Emulsion Copolymerization of Tetrafluoroethylene with Propylene. II. Formulas and Conditions

Abstract Formulas and reaction conditions for the radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene were studied at room temperature in the presence of gaseous monomers containing 50 mole % tetrafluoroethylene content. Stable latex was obtained by the use of ammonium perfluorooctanoate emulsifier. The resulting copolymer was a rubberlike material. A percentage of emulsifier greater than 1 wt% to water was suitable in this emulsion copolymerization. The conversion and the molecular weight were independent of the stirring speed above 400 rpm and decreased with a rise in temperature. An induction period was observed in the presence of oxygen. There was no effect of water purity on the emulsion copolymerization. When the stainless-steel reaction vessel was cleaned with a dilute acidic aqueous solution, the conversion was almost the same as that for a Pyrex reaction vessel.

Formation of free radicals in the reduction of chlorate by the iron(II) cation in dilute aqueous acid solution

The effect of alcohols on the rate of oxidation of the iron(II) cation by chlorate provides evidence for the intermediate formation of the active free radicals ·OCl and ·Cl.

The thermodynamics and kinetics of the polymerization of silicic acid in dilute aqueous solution

The polymerization of silicic acid has been investigated at a pH of 8.5 and initial monomer concentration of 300 p.p.m. The rate of polymerization was determined at 25, 30, 35, 40 and 45°C so that the activation energies could be calculated. The activation energies were found to be −16±4 kcal/mole in the 25–35°C region and 14±4 kcal/mole in the 35–40°C region. The negative activation energy is explained by assuming a pre-equilibrium step involving a hydrogen bonded species. The thermodynamic parameters were also determined for the polymerization process. A mechanism has been proposed for the polymerization reaction.

The separation and determination of low-molecular-weight (C 2—C 10) straight-chain carboxylic acids in dilute aqueous solution by the gas chromatography of their p-bromophenacyl and P-phenylphenacyl esters

The quantitative and qualitative analysis of acetic, propionic, n-butyric, n-valeric, n-hexoic, n-heptoic, n-octoic, n-nonoic and n-decanoic acids present in dilute aqueous media as free acids or salts, in the presence of mineral acids or bases, is described. The p-bormophenacyl or p-phenylphenacyl esters of the acids were formed and injected into 2.5% sodium dodecylbenzene sulphonate or 1% Apiezon L or a 1:1 mixture of the two (depending on which acids were present) coated on acid-washed washed 60/80 mesh Chromosorb G packed in a 6-ft. glass column.

Diazepines. Part XIV. Reactivities of positions 5 and 6 in 2,3-dihydro-1,4-diazepines towards quasi-aromatic substitution by bromine

Simple theory predicts that in a 2,3-dihydro-1,4-diazepine or its mono-cation a proton at position 6 should be much more reactive towards electrophilic substitution than protons at positions 5 and 7. The measured rate of bromination at position 6 of the 5-methyl-7-phenyl derivative in dilute aqueous acid solution was 2·4 × 106 l mol–1 s–1 and that of the 1,4,5,7-tetramethyl derivative was approximately similar, in concordance with an earlier value for the 5,7-dimethyl derivative. The 6-methyl and 1,4,6-trimethyl derivatives, though unsubstituted at positions 5 and 7, reacted rapidly in a different way at position 6, giving non-conjugated products which were hydrolysed. 2-lmidazoline, used as an alternative model compound, failed to react with bromine or chlorine, in agreement with expectation.

Determination of formic acid in dilute aqueous solution and separation and determination of aniline and toluidine isomers by gas chromatography of formanilide and formyl toluidides

The determination of formic acid in various aqueous conditions (as free acid and as a salt in the presence of mineral or other carboxylic acids) by the gas chromatography of the formyl derivatives of aniline and o-, m- and p-toluidine is described. The analysis for these four amines and N-methyl aniline and N-methyl p-toluidine in aqueous and non-aqueous mixtures by the gas chromatography of either their formyl or their unsubstituted acetyl derivatives is also described. Columns of sodium dodecylbenzenesulphonate coated on Chromosorb G are used for the chromotography in both cases.

Further studies on polymerizations in interacting polymer systems

Further studies have been carried out on the polymerization of acrylic acid in dilute aqueous solution in the presence of polymeric molecules known to interact with the polyacrylic acid. In the presence of polyethylene imine, a large increase in rate of polymerization was observed dependent on the concentration of the polyethylene imine. In the presence of polyethylene oxide, much less effect was observed; the increase in rate of polymerization was due apparently to the system becoming heterogeneous as polymerisation proceeded.

Polymerization in an interacting polymer system

The influence of polyvinyl pyrrolidone (PVP) on the polymerization of acrylic acid in dilute aqueous solution has been studied. The fact that the system becomes heterogeneous has been used to provide a turbidimetric method for following the polymerization. The rate of polymerization has been found to depend on the concentration of PVP, reaching a maximum at close to equimolar concentrations, based on monomer units. The kinetics of the system have been studied and have been found to exhibit characteristics of both heterogeneous polymerizations, and what might be expected of a “replica polymerization”. The complex formed as a result of the polymerization has been examined by intrinsic viscosity and electrophoresis studies, and has been found to consist apparently of PVP, polyacrylic acid (PAA) and a graft copolymer of these polymers.

Equations for Activity Coefficient of Hydrochloric Acid in Dilute Aqueous Solutions between 5 and 45°C

Equations for Activity Coefficient of Hydrochloric Acid in Dilute Aqueous Solutions between 5 and 45°C

A study of perfectly mixed photochemical reactors

AbstractThe performance of a perfectly mixed photochemical reactor has been analyzed for systems having low light absorption coefficients. The analysis has been tested by an experimental study of the decomposition of hexachloroplatinic acid in dilute aqueous solution. Results tend to verify the analysis, but indicate the need for additional experimental work.

The Radiation-Induced Exchange of Chlorine between Chloride and Trichloroacetic Acid

Decompositions by ionizing radiation of simple carboxylic acids in aqueous solutions have been studied by several investigators. Garrison and co-workers (1-7) have studied the radiation-induced decompositions of acetic acid, formic acid, and glycine solutions under a variety of conditions. In general, the experimental results were adequately explained on the basis of free radical reactions involving H, OH, and H202 from solvent water. Hayon and Weiss (8) have studied the radiation(200-kv X-ray) induced decompositions of monochloroacetic and trichloroacetic acids. The products observed from monochloroacetic acid in dilute aqueous solutions which had been degassed prior to irradiation were chloride, formaldehyde, glyoxalic acid, hydrogen peroxide, hydrogen, oxygen, carbon dioxide, and carbon monoxide. Their results indicated that reactions 1 to 5 were involved in this decomposition. These reactions are analogous to those proposed for the decomposition of other simple carboxylic acids.

A Comparison of the Effects of X-Rays and Alpha Rays on Some Proteins and Amino Acids in Dilute Aqueous Solution

S>Serum albumin, ribonuclease, tryptophan, tyrosine, and some other amino acids in dilute aqueous solution were irradiated with x (or beta ) and alpha rays, and changes were observed in sedimentation of serum albumin and in the absorption spectra of all the materials. For serum albumin the effects of x and alpha radiations differed, and, although the protein could be protected by the addition of cysteine against x radiation, there was little protection against alpha radiation. No oxygen effect was noted for either radiation. The protein was little affected by hydrogen peroxide but was attacked by ozone to produce changes closely similar to those after alpha irradiation, although the effect of alpha radiation was not brought about by ozone. Alpha radiation attacked the indole ring of tryptophan twice as readily as did x radiation. The spectral changes found on the alpha irradiation of tryptophan closely matched those appearing on the alpha irradiation of serum albumin. The effects of x radiation on tryptophan could be greatly reduced by adding protective compounds to the solution, but tryptophan was protected against alpha radiation to a much lesser extent. It is proposed that the action of x radiation on proteins is exerted by free radicalsmore » which attack all the common amino acids, whereas the action of alpha radiation is by a short-lived molecular product which preferentially attacks the tryptophan residue or molecule. It is proposed that the molecular species concerned is a metastable excited state of hydrogen peroxide. Consideration is given to the role of the molecular product of alpha radiation in determining the relative biological efficiencies of densely and sparsely ionizing radiations.« less

Studies on the Analysis of Surface Active Agents. XIV.

For the rapid and accurate determination of anionics, a new volumetric method, “4-Amino-4'-Chlorobiphenyl Hydrochloride Diazotitration Method” has been developed. The active component of anionics is precipitated in dilute acidic aqueous solution with 4-amino-4'-chlorobiphenyl hydrochloride (ACBH), and the excess of ACBH in the filtrate is titrated back with sodium nitrite standard solution by diazotitration, using potassium-iodide-starch paper until it turns blue.The experimental results with various anionics showed that the new method was quite satisfactory. Higher mole-ratio of ACBH to anionics than 6 resulted too high analytical values. Potassium-iodide-starch paper showed clearer end point of diazotitration than p-dimethyl-aminobenzaldehyde test paper in this new method.

Biogeochemistry of organic matter—I: Polypeptides and amino acids in fossils and sediments in relation to geothermometry

Quantitative data are presented on ninhydrin-reacting substances in hydrolysates and extracts of Recent sediments, sedimentary rocks, and fossils, as determined by column chromatography. The recovery of amino acids added in small amounts to a concentrated calcium chloride solution was found to be 94-96 per cent, after precipitation of the calcium as calcium sulphate and removal of the HCl by vacuum distillation. Seventeen amino acids and three unknowns were detected in hydrolysates of surface and subsurface sediment samples, from Lake Opinicon, Ontario, with amino acids and other ninhydrin-reacting organic compounds accounting for nearly two-thirds of the soluble-N in the hydrolysate, and ammonia for most of the remaining third. Only five amino acids, (aspartic acid, glutamic acid alanine, leucine(s) and γ-aminobutyric acid) and one unidentified ninhydrin-reacting organic compound were present in a hydrolysate of shale from the Green River formation, (Eocene). Amino acids accounted for only 0.014 per cent of the total-N in the shale. It was calculated from the alanine content that the maximum temperature that the Green River shale could have been continuously subjected to during its history was 74°C. Amino acids were not detected in hydrolysates of two pre-Cambrian sedimentary rocks, nor in it hydrolysate of a Miocene lignite. An acid extract of carnosaur "teeth" from the Upper Cretaceous contained leucine(s), ammonia, ethanolamine, and one unidentified ninhydrin-reacting substance that chromatographed similarly to an unknown found in a hydrolysate of laboratory heated Mercenaria shells. Of the total-N in a shell of the univalve mollusc Casis Madagascarensis, 50 per cent was extractable with cold HCl, this fraction consisting of amino acids, ammonia and unidentified compounds, some of which reacted with ninhydrin. Only 57 per cent of the nitrogen in a hydrolysate of the conchiolinfraction of the shell was recovered in the form of amino acids and ammonia. Fifteen amino acids and two unknowns were detected in the hydrolysate of the conchiolin-fraction. The periostracum of a Pleistocene Mercenaria mercenaria shell liberated sixteen amino acids and three unidentified ninhydrin-reacting substances on acid hydrolysis. The periostracum-free fossil shell had approximately the same amino acid composition as reported elsewhere for shells of living Mercenaria. Quantitative data on amino acids and other ninhydrin-roacting compounds were reported for samples of Pleistocene Mercenaria shells pyrolysed in the laboratory at 213 and 219x000B0;C. In the shell, alanine decomposed at a faster rate, and plienylalanine at an equal or slower rate, than the rates characteristic of the same amino acids in dilute aqueous solution. The nitrogen liberated from amino acids during pyrolysis could mostly be accounted for in the hydrolysates as acid-insoluble-N, ammonia, and soluble nitrogenous compounds, some of which reacted with ninhydrin. Amines were detected only in samples pyrolysed in sealed tubes.

Role of oxygen in the cross-linking and degradation of deoxyribonucleic acid by ionizing radiations.

WHEN deoxyribonucleic acid in dilute aqueous solutions is irradiated with X-rays, the attack by the free radicals produced in water leads to main-chain scission, and this reaction is essentially the same in the presence as in the absence of oxygen1. Irradiation of nucleic acid in the solid state and containing less than 25 per cent of water leads to a complex series of reactions which, judged by physico-chemical measurements, were largely unaffected by oxygen. With nucleic acid gels having a water content between these two extremes, oxygen was found to exert a pronounced influence on the changes produced by irradiation with 1-MeV. electrons. Since deoxyribonucleic acid is present in the cells in the form of a relatively concentrated gel, the response to radiation in this form is more likely to be of biological significance than the behaviour of dilute solutions or nearly dry solid.

Chemical effects of ionizing radiation on deoxyribonucleic acid in dilute aqueous solution.

WHEN purine and pyrimidine nucleotides in dilute aqueous solution are irradiated with ionizing radiation they are destroyed by two pathways1. The minor pathway is attack upon the sugar moiety followed by release of free base1. Details of the mode of sugar attack have not been established; but possible reactions have been suggested by Daniels et al. 2. The major pathway is attack of the base moiety which with purines in the absence of oxygen yields the corresponding formamido-pyrimidine nucleotide3. When pyrimidine nucleotides are irradiated in the absence of oxygen sugar phosphate is liberated, but there is no ultra-violet absorbing product arising from base attack. When oxygen is present during irradiation G-values (molecules per 100 eV.) for nucleotide destruction are increased 2–3 times4. For purine nucleotides the increased degradation in oxygen is almost entirely an augmented base attack, but no ultra-violet product arising from it is found4. When pyrimidines are irradiated in the presence of oxygen hydroxy-hydroperoxides are formed5. G-values for destruction of pyrimidines in the presence of oxygen are greater than those for purines1,6 and suggest that when deoxyribonucleic acid is irradiated pyrimidines will be destroyed to a greater extent. Extrapolation of the effects of radiation upon nucleotides to effects upon deoxyribonucleic acid is complicated in an uncertain way by the influence of inter-nucleotide linkages and hydrogen bonding of base pairs. This communication reports the amounts of base and sugar destroyed when aqueous solutions of calf thymus deoxyribonucleic acid are irradiated.