The Interactions of Aqueous Solutions of Chlorine with Citric Acid. A Source of Mutagens. (A Preliminary Report)

Abstract

Citric acid, an additive to an important acrylamide based polymeric flocculant, was found to react with an aqueous solution of chlorine to give several chlorinated propanones, di- and trichloroacetic acid, chloroform, and a number of as yet unidentified chlorine containing compounds. Formation of these alledged carcinogens and mutagens also takes place by treating diluted aqueous solutions of frozen orange juice concentrate with such chlorine solutions. The formation and ratios of the detected chlorinated compounds is pH-dependent. A tentative scheme which could account for these findings is presented.     

The determination of nitrogen trichloride in liquid chlorine

Methods are described for the determination of nitrogen trichloride over the range of concentrations at which it exists in chlorine manufacture and handling. The methods are based on the conversion of nitrogen trichloride to ammonium chloride by hydrochloric acid and the determination of ammonium by spectrophotometry as the indophenol complex or by potentiometry with an ammonia gas-sensing electrode; higher levels of nitrogen trichloride are determined by titration. For liquid chlorine, a sample is taken in a refrigerated trap containing hydrochloric acid. After that, the chlorine is slowly evaporated at atmospheric pressure. Results of tests are given to prove the reliability of the methods.     

Absorption of chlorine into water

Solubility and diffusion data have been used to describe absorption of chlorine into water. When the gas dissolves in water, hydrochloric acid produced by partial hydrolysis of molecular chlorine diffuses rapidly into the bulk liquid. Because the surface of the absorbent is depleted in hydrochloric acid, the solubility of chlorine in the interfacial liquid is significantly higher than the equilibrium solubility at the same chlorine partial pressure. During desorption of dissolved chlorine, hydrochloric acid diffuses from the interior and collects in the interfacial region. Differential equations for absorption and desorption with coupled flow of a second solute component are solved numerically. Calculated concentration profiles are in good agreement with profiles estimated by chemical analysis of layers of absorbent.     

Chlorine atom and ClO wall reaction products

The products of the heterogeneous reactions of chlorine atoms and chlorine oxide radicals with acid coated Pyrex walls have been directly determined for the first time. Contrary to the usual assumption that chlorine atoms recombine to form Cl₂, we find that the major product is HCl, with small amounts of perchlorate also formed. Similarly, ClO radicals form HCl rather than Cl₂. The source of hydrogen for these reactions is probably the water always found in this type of vacuum system. These results may change the interpretation of flow tube experiments with chlorine atoms. Application to the H + HCl reaction is discussed as an example.     

Rapid Determination of HAAs Formation Potential of the Reaction of Humic Acid with Chlorine or Chlorine Dioxide

On the basis of gas chromatography(GC) coupled with a short capillary column and an electron capture detector(ECD), a simple and rapid method for the determination of five haloacetic acids(HAAs) in drinking water was developed by the optimization of derivation conditions and the modification of gas chromatographic program. HAAs formation potential(HAAFP) of the reaction of humic acid with chlorine was determined via this method. The major advantages of the method are the simplicity of chromatographic temperature program and the short run time of GC. Dichloroacetic acid(DCAA) and Trichloroacetic acid(TCAA), which were detected in the determination of HAAFP, were rapidly formed in the first 72 h of the reaction of humic acid with chlorine. HAAFP of the reaction of humic acid with chlorine increased with the increase in the concentrations of humic acid and chlorine. The average HAAFP of the reaction of humic acid with chlorine was 39.9 μg/mg TOC under the experimental conditions. When the concentration of humic acid was 4 mg/L, the concentration of HAAs, which were produced in the reaction of humic acid with chorine, may exceed MCL of 60 μg/L HAAs as the water quality standards for urban water supply of China and the first stage of US EPA disinfection/disinfection by-products(D/DBP) rule; when the concentration of humic acid was 2 mg/L, the concentration of HAAs may exceed MCL of 30 μg/L HAAs for the second stage of US EPA D/DBP rule. When humic acid was reacted with chlorine dioxide, only DCAA was detected with a maximum concentration of 3.3 μg/L at a humic acid content of 6 mg/L. It was demonstrated that the substitution of chlorine dioxide for chorine may entirely or partly control the formation of HAAs and effectively reduce the health risk associated with disinfected drinking water.     

Allylic halogenation of unsaturated amino acids

A range of dehydro amino acid derivatives has been prepared and subjected to halogenation using either molecular bromine or chlorine, or NBS. Allylic halogenation of the unsaturated amino acid side chains occurs through radical bromination with NBS. The procedure is complementary to treatment with chlorine, which also affords allyl halides. This latter and unusual reaction is shown through a deuterium labelling study to proceed via an ionic mechanism. The choice of NBS or chlorine for allyl halide synthesis is shown to depend on the potential to avoid competing reactions, such as halolactonization of leucine derivatives with chlorine, and hydrogen abstraction and bromine incorporation at multiple sites on treatment of isoleucine derivatives with NBS. The synthetic utility of the allyl halides prepared in this study is indicated through the synthesis of a cyclopropyl amino acid derivative and the extension of the carbon skeleton of an amino acid side chain.     

Travelling wave in the chlorite-thiourea reaction

The oxidation of thiourea by chlorite within the pH range of 2 to 5.5 has been found to produce a single wave of chlorine dioxide in unstirred solutions. The wave has been studied in narrow tubes of varying diameters and in petri dishes. The wave appears after an induction period that depends on the acid concentration, the [ClO₂^?]/[CS(NH₂)₂] ratio, the temperature, and the diameter of the tube. The wave starts from the surface in a tube and from the edges in a petri dish. The rate of wave movement is proportional to the ratio and the acid concentration. Barium chloride and starch were used as indicators. The wave could be initiated electrochemically and by addition of a drop of solution containing chlorine dioxide. The chlorine dioxide is produced by the oxidation of chlorite by hypochlorous acid.     

Fonctionnalisation du polychlorure de vinyle: Greffage de fonctions plastifiantes (type ester d'éthyle-hexyle)

The grafting of plasticizing groups such as 2-ethyl-hexyl ester on PVC has been carried out either in solution or in the gel state through nucleophilic substitution of chlorine atoms, with the help of sodium salts of 2-ethyl-hexyl esters of o-mercaptobenzoic acid and thioglycollic acid. As with sodium thiophenate, the substitution of chlorine atoms is stereoselective with respect to iso and heterotactic triads. The glass transition temperature is lowered as the substitution rate increases and the plasticizing power of grafted 2-ethyl-hexyl ester groups of thioglycollic acid is greater than those introduced by o-mercaptobenzoic acid. Further the plasticizing power of 2-ethyl-hexyl ester groups is decreased when they are grafted on the polymer.     

S-oxygenation of thiocarbamides II: Oxidation of trimethylthiourea by chlorite and chlorine dioxide

The kinetics of the oxidation of a substituted thiourea, trimethylthiourea (TMTU), by chlorite have been studied in slightly acidic media. The reaction is much faster than the comparable oxidation of the unsubstituted thiourea by chlorite. The stoichiometry of the reaction was experimentally deduced to be 2ClO2- + Me2N(NHMe)C=S + H2O --> 2Cl- + Me2N(NHMe)C=O + SO4(2-) + 2H+. In excess chlorite conditions, chlorine dioxide is formed after a short induction period. The oxidation of TMTU occurs in two phases. It starts initially with S-oxygenation of the sulfur center to yield the sulfinic acid, which then reacts in the second phase predominantly through an initial hydrolysis to produce trimethylurea and the sulfoxylate anion. The sulfoxylate anion is a highly reducing species which is rapidly oxidized to sulfate. The sulfinic and sulfonic acids of TMTU exists in the form of zwitterionic species that are stable in acidic environments and rapidly decompose in basic environments. The rate of oxidation of the sulfonic acid is determined by its rate of hydrolysis, which is inhibited by acid. The direct reaction of chlorine dioxide and TMTU is autocatalytic and also inhibited by acid. It commences with the initial formation of an adduct of the radical chlorine dioxide species with the electron-rich sulfur center of the thiocarbamide followed by reaction of the adduct with another chlorine dioxide molecule and subsequent hydrolysis to yield chlorite and a sulfenic acid. The bimolecular rate constant for the reaction of chlorine dioxide and TMTU was experimentally determined as 16 +/- 3.0 M(-1) s(-1) at pH 1.00.     

Chlorine-35/37 NMR spectroscopy of solid amino acid hydrochlorides: refinement of hydrogen-bonded proton positions using experiment and theory

Trends in the chlorine chemical shift (CS) tensors of amino acid hydrochlorides are investigated in the context of new data obtained at 21.1 T and extensive quantum chemical calculations. The analysis of chlorine-35/37 NMR spectra of solid L-tryptophan hydrochloride obtained at two magnetic field strengths yields the chlorine electric field gradient (EFG) and CS tensors, and their relative orientations. The chlorine CS tensor is also determined for the first time for DL-arginine hydrochloride monohydrate. The drastic influence of 1H decoupling at 21.1 T on the spectral features of salts with particularly small 35Cl quadrupolar coupling constants (CQ) is demonstrated. The chlorine CS tensor spans (Omega) of hydrochloride salts of hydrophobic amino acids are found to be larger than those for salts of hydrophilic amino acids. A new combined experimental-theoretical procedure is described in which quantum chemical geometry optimizations of hydrogen-bonded proton positions around the chloride ions in a series of amino acid hydrochlorides are cross-validated against the experimental chlorine EFG and CS tensor data. The conclusion is reached that the relatively computationally inexpensive B3LYP/3-21G* method provides proton positions which are suitable for subsequent higher-level calculations of the chlorine EFG tensors. The computed value of is less sensitive to the proton positions. Following this cross-validation procedure, /CQ(35Cl)/ is generally predicted within 15% of the experimental value for a range of HCl salts. The results suggest the applicability of chlorine NMR interaction tensors in the refinement of proton positions in structurally similar compounds, e.g., chloride ion channels, for which neutron diffraction data are unavailable.     

Fiber-optic chlorine probe based on fluorescence decay of N-(6-methoxyquinolyl)acetoethyl ester

A fiber-optic probe for measuring chlorine in aqueous solution is evaluated. The probe uses a microporous gas-permeable membrane to trap a small volume of aqueous internal solution made of N-(6-methoxyquinolyl)acetoethyl ester (MQAE) in front of a fiber-optic assembly. The working principle of this probe is based on a combination of fluorescence quenching and redox reaction of MQAE by chloride ion and chlorine, respectively. While the magnitude of total fluorescence decay is independent of the sample concentration, the initial rate of decrease in fluorescence intensity is linearly proportional to the chlorine concentration over the range from 8.4 to 418 microM. Once the probe is exposed to a chlorine sample, the probe tip must be refilled with a fresh aliquot of the internal solution before the next measurement. In this mode, the probe displays excellent reproducibility; the relative standard deviation of the initial rate of fluorescence decay (n = 3) is only 1 percent. This probe can also be used for the measurement of hypochlorous acid (HOCl) in aqueous solution. The response properties are identical to those of the chlorine probe.     

Carbonylation of chlorobiphenyls catalyzed by modified cobalt carbonyl

Dichlorobiphenyls having both chlorine atoms in the same benzene ring undergo mild carbonylation in the presence of 1,2-epoxypropane-modified carbonyl cobalt complex to give biphenylcarboxylic acid esters. Monochlorobiphenyls fail to react under analogous conditions. The rate and selectivity of the reaction depend on the position of chlorine atoms. Carbonylation of dichlorobiphenyls having a chlorine atom in the meta position occurs preferentially at that position. 2,4-Dichlorobiphenyl gives rise mainly to the carbonylation product at the 2-position.     

Symmetrical and unsymmetrical incorporation of active biological monomers on the surface of phosphorus dendrimers

Phosphorus-containing dendrimers are attractive carriers for the delivery of bioactive molecules due to their very particular architecture, globular shape and chemical and physical properties. Herein we report a simple synthetic approach of ethacrynic acid derivatives loaded-phosphorus dendrimers by symmetrical grafting of ethacrynic acid analogues by nucleophilic substitution of each chlorine of P(S)Cl₂ end groups. We report also for the first time an unsymmetrical grafting of two different phenol derivatives by a selective substitution of one chlorine of P(S)Cl₂ end group followed by the grafting of the second phenol.     

Chloration et S-oxydation du benzo[b]thiophène par l'hypochlorite de tertiobutyle. Mécanisme de la réaction

In the reaction with benzothiophene, t-butyl hypochlorite acts simultaneously as a smooth oxidizing agent and as a chlorinating agent since it is a source of both hypochlorous acid and chlorine. The mixture of all the products obtained imply that the reaction intermediate is the unstable benzothiophene I-oxide which was shown to be present by the stop flow technique. The chlorine formed traps the highly reactive benzothiophene 1-oxide in situ to give the observed products.     

The Intehaction of Aqueous Solutions of Chlorine with Malic Acid,Tartaric Acid,and Various Fruit Juices: A Source of Mutagens

Abstract

The interactions of aqueous solutions of chlorine with some fruit acids (citric acid, DL-malic acid, arid L-tartaric acid) at different pH values were studied. Diethyl ether extraction followed by GC/MS analysis indicated that a number of mutagens (certain chlorinated propanones and chloral hydrate) are present as major products in some of these samples. A number of fruit juices (orange, grape, apple, pineapple, and grapefruit) were also treated with aqueous solutions of chlorine at their pH values. The products were analyzed by GC/MS. The same mutagens that were formed by the pure acids (citric acid and DL-malic acid) were identified as major products in ether extracts of these samples. Another mutagen, dichloroacetonitrile, was also identified as a minor product in some of these juice samples. All of the major products observed in the chlorination of all five fruit juices are potentially derived from reactions of aqueous solutions of chlorine with citric or malic acid and with trace amounts of acetaldehyde and acetone in the juices. The minor product, dichloroacetonitrile, is likely derived from the chlorination of certain amino acids in the fruit juices.     

Aromatic chlorination of omega-phenylalkylamines and omega-phenylalkylamides in carbon tetrachloride and alpha,alpha,alpha-trifluorotoluene

The aromatic halogenation of simple alkylbenzenes with chlorine proceeds smoothly in acetic acid but is much less efficient in less polar solvents. By contrast chlorination of omega-phenylalkylamines, such as 3-phenylpropylamine, occurs readily in either acetic acid, carbon tetrachloride or alpha,alpha,alpha-trifluorotoluene, and in the latter solvents gives high proportions of ortho-chlorinated products. These effects are attributable to the involvement of N-chloroamines as reaction intermediates, with intramolecular delivery of the chlorine electrophile. Omega-phenylalkylamides, such as 3-phenylpropionamide, also easily undergo aromatic chlorination in carbon tetrachloride and alpha,alpha,alpha-trifluorotoluene. These reactions generally show a first-order dependence on the substrate concentration, but not on the amount of chlorine. With carbon tetrachloride, very similar reaction rates are observed with chlorine concentrations ranging from 0.1-1.5 M. In alpha,alpha,alpha-trifluorotoluene, the rates reach a plateau at a chlorine concentration of approximately 0.2 M. These features indicate that the reactions proceed via the formation of intermediates which evidence suggests may be the corresponding O-chloroimidates. Irrespective of the mechanistic details, the reactions are remarkably rapid, being faster than analogous reactions in acetic acid and three to four orders of magnitude more rapid than reactions of simple alkylbenzenes in carbon tetrachloride. Therefore, chlorination of the amines and amides may be accomplished without the need for highly polar solvents, added catalysts or large excesses of chlorine, which are often employed for electrophilic aromatic substitutions. Although the use of carbon tetrachloride is becoming increasingly impractical due to environmental concerns, the trifluorotoluene is a suitable alternative.     

Oxyhalogen-sulfur chemistry: kinetics and mechanism of oxidation of N-acetylthiourea by chlorite and chlorine dioxide

The oxidation reactions of N-acetylthiourea (ACTU) by chlorite and chlorine dioxide were studied in slightly acidic media. The ACTU-ClO(2)(-) reaction has a complex dependence on acid with acid catalysis in pH > 2 followed by acid retardation in higher acid conditions. In excess chlorite conditions the reaction is characterized by a very short induction period followed by a sudden and rapid formation of chlorine dioxide and sulfate. In some ratios of oxidant to reductant mixtures, oligo-oscillatory formation of chlorine dioxide is observed. The stoichiometry of the reaction is 2:1, with a complete desulfurization of the ACTU thiocarbamide to produce the corresponding urea product: 2ClO(2)(-) + CH(3)CONH(NH(2))C=S + H(2)O --> CH(3)CONH(NH(2))C=O + SO(4)(2-) + 2Cl(-) + 2H(+) (A). The reaction of chlorine dioxide and ACTU is extremely rapid and autocatalytic. The stoichiometry of this reaction is 8ClO(2)(aq) + 5CH(3)CONH(NH(2))C=S + 9H(2)O --> 5CH(3)CONH(NH(2))C=O + 5SO(4)(2-) + 8Cl(-) + 18H(+) (B). The ACTU-ClO(2)(-) reaction shows a much stronger HOCl autocatalysis than that which has been observed with other oxychlorine-thiocarbamide reactions. The reaction of chlorine dioxide with ACTU involves the initial formation of an adduct which hydrolyses to eliminate an unstable oxychlorine intermediate HClO(2)(-) which then combines with another ClO(2) molecule to produce and accumulate ClO(2)(-). The oxidation of ACTU involves the successive oxidation of the sulfur center through the sulfenic and sulfinic acids. Oxidation of the sulfinic acid by chlorine dioxide proceeds directly to sulfate bypassing the sulfonic acid. Sulfonic acids are inert to further oxidation and are only oxidized to sulfate via an initial hydrolysis reaction to yield bisulfite, which is then rapidly oxidized. Chlorine dioxide production after the induction period is due to the reaction of the intermediate HOCl species with ClO(2)(-). Oligo-oscillatory behavior arises from the fact that reactions that form ClO(2) are comparable in magnitude to those that consume ClO(2), and hence the assertion of each set of reactions is based on availability of reagents that fuel them. A computer simulation study involving 30 elementary and composite reactions gave a good fit to the induction period observed in the formation of chlorine dioxide and in the autocatalytic consumption of ACTU in its oxidation by ClO(2).     

Ceric Ammonium Nitrate as the Novel Oxidizing Agent for the Facile Synthesis of (Dichloroiodo)arenes

Ceric ammonium nitrate (CAN) has been found to be a remarkable oxidizing agent for the oxidative conversion of iodoarenes to (dichloroiodo)arenes in acetic acid using aqueous HCl. The reaction of CAN with HCl generates in situ molecular chlorine, which is responsible for the oxidation. This method avoids the use of hazardous, toxic, and corrosive gaseous chlorine.     

An ion-selective electrode method for determination of chlorine in geological materials

A method is presented for the determination of chlorine in geological materials, in which a chloride-selective ion electrode is used after decomposition of the sample with hydrofluoric acid and separation of chlorine in a gas-diffusion cell. Data are presented for 30 geological standard materials. The relative standard deviation of the method is estimated to be better than 8% for amounts of chloride of 10 mug and greater.     

Reactivity of methyl (3,6-dichloropyridazin-4-yl)acetate towards nucleophiles

Methyl (3,6-dichloropyridazin-4-yl)acetate (II), prepared from methyl (3,6-dihydroxypyrid-azin-4-yl)aeetate (1) by chlurination with phosphorus oxychloride, was used for studies of nucleo-philic displacement reactions and it has been found that only the chlorine atom at position 6 was displaced with hydrazine. With diluted hydrochloric acid both chlorine atoms were displaced with the 6-oxo isomer predominating. By turning the aromatic ring of pyridazine into an o-quinoid system, the chlorine atom at position 3 became mobile. Cyelization of (6-hydrazino-s-triazolo-[4,3-b ]pyridazin-7-yl)acetic acid hydrazide (XIX) gave 6-aminopyrrolo[3,2-e ]s-triazlo[ 4,3-b ]-pyridazm-7(8H)one (XXI).