Ortho Chlorine Atoms Research Articles

Introducing of modeling techniques in the research of POPs in breast milk – A pilot study

This study used advanced statistical and machine learning methods to investigate organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in breast milk, assuming that in a complex biological mixture, the pollutants emitted from the same source or with similar properties are statistically interrelated and possibly exhibit non-linear dynamics. The elaborated analyses such as Unmix source apportionment characterized individual source groups, while guided regularized random forest indicated the pollutant dependence on the ortho-chlorine atom attached to the congener's phenyl ring and mother's age. Mutual associations among PCBs were further discussed, but the results implied they were mostly not related to child delivery. PCB congeners −153, −180, −170, −118, −156, −105, and −138 appeared to be compounds of the outmost importance for mutual prediction with reference to their interrelations regarding chemical structure and metabolic processes in the mother's body. Finally, machine learning methods, which provided prediction relative errors lower than 30% and correlation coefficients higher than 0.90, suggested a possible strong non-linear relationship among the pollutants and consequently, the complexity of their pathways in the breast milk.

Stepwise ortho Chlorination of Carboxyl Groups for Promoting Structure Variance of Heterometallic Uranyl-Silver Coordination Polymers of Isonicotinate.

We report the syntheses and characterization of four new heterometallic uranyl-silver compounds from isonicotinic acid derivatives with a stepwise ortho chlorination of carboxyl group, that is, isonicotinic acid (H-PCA), 3-chloroisonicotinic acid (H-3-MCPCA), and 3,5-dichloroisonicotinic acid (H-3,5-DCPCA). Compound 1, (UO2)Ag4(3,5-DCPCA)6(3,5-DCPy)2, from H-3,5-DCPCA displays a heterometallic three-dimensional (3D) framework through the connection of 3,5-DCPCA and in situ-formed 3,5-dichloropyridine (3,5-DCPy) with the aid of multiple argentophilic interactions. Compounds 2 ((UO2)Ag(3-MCPCA)3) and 3 ((UO2)Ag2(3-MCPCA)4), which differ from each other in coordination modes of uranyl center, are both heterometallic 3D reticular frameworks from 3-MCPCA based on highly coordinated silver nodes. All these heterometallic uranyl-silver compounds are different from the hydrothermal products from chlorine-free H-PCA ligand in the presence of uranyl and silver ions, U-Ag-PCA ((UO2Ag(OH)(PCA)2)) and 4 ((UO2)Ag2(OH)(H2O)2(PCA)4) due to highly coordinated silver ions found in 1-3, among which carboxyl groups of isonicotinate expected to coordinate with uranyl are the biggest contributors. Detailed structural analysis reveals that the inclination of the carboxyl group of isonicotinate driven by large steric hindrance from bulky ortho chlorine atoms at its ortho positions enables it to participate in the coordination sphere of silver ion and promote the formation and structure variance of 3D heterometallic uranyl-silver frameworks.

Reductive dechlorination of polychlorinated biphenyls (PCBs) by ultrasound-assisted chemical process (UACP)

The dechlorination of aqueous polychlorinated biphenyls (PCBs) using the ultrasound-assisted chemical process (UACP), which is a combination of ultrasonic irradiation and radical generations using di-tert-butyl peroxide as a radical initiator and ferrous ion as a catalyst at moderate temperature in alkaline 2-propanol, was demonstrated with a high reduction of PCBs. A commercial PCB-containing compound, Aroclor 1260, was also decomposed with the removal efficiency of 97 % achieved within 3 h of UACP. The gas chromatograph was used as a quantitative method to measure the decomposition rate of PCBs. The competitive elimination among the ortho (2-position), meta (3-position), and para (4-position) chlorine atoms of PCB was also identified.

Theoretical study of thermochemical and structural parameters of chlorinated isomers of aniline

Thermochemical parameters, in terms of standard enthalpies of formation, standard entropies and Gibbs free energies of formation and heat capacities are calculated herein for all chlorinated isomers of aniline. Calculated values of standard enthalpies of formation are in agreement with the available experimental values. Calculated values of solvation energies indicate that the interaction of chlorinated aniline with water molecules decreases with the degree of chlorination. Trends in angles and barriers of inversion indicate that the pyramidalisation in chlorinated aniline decreases with the degree of chlorination. The most stable isomer in each homologue group is highlighted. Interaction of ortho chlorine atoms with the electron donating group of amine affords ortho-substituted isomers slight stability over other isomers.

Features of the molecular structure of compounds of (Cl3PNAr)2 series (Ar = C6H4Z, Z = H, Cl) by quantum-chemical calculations and the data of 35Cl nuclear quadrupole resonance

A series of dimeric molecules (Cl3PNAr)2 where Ar = C6H4Z, Z = H or Cl in 2–4 positions, was calculated by the RHF/6-31G* method with the full geometry optimization. A specific nature of the intramolecular steric orientation of aryl groups was revealed, therewith in the case Ar = C6H4Cl-2 short nonvalent contacts were founf between the ortho-chlorine atom and PCl3 group manifested in the peculiarity of geometric parameters and NQR spectroscopy data of this compound. The correlation of the 35Cl NQR frequencies of P-Cl bonds with the values of the charges on the chlorine atoms obtained by quantum-chemical calculations of the molecules was analyzed.

N-(2,3-Dichlorophenyl)-4-methylbenzenesulfonamide

The title compound, C13H11Cl2NO2S, contains two molecules in the asymmetric unit in which the dihedral angles between the benzene rings are 76.0 (1) and 79.9 (1)°. The conformations of the N—H bonds with respect to their adjacent ortho-chlorine atoms are syn. In the crystal, N—H⋯O hydrogen bonds link the molecules into dimers.

QSPRs for the estimation of subcooled liquid vapor pressures of polycyclic aromatic hydrocarbons, and of polychlorinated benzenes, biphenyls, dibenzo- p-dioxins, and dibenzofurans at environmentally relevant temperatures

This study aims to develop estimation procedures for subcooled liquid vapor pressures of polycyclic aromatic hydrocarbons (PAHs), and of polychlorinated benzenes, biphenyls (PCBs), dibenzo- p-dioxines (PCDDs), and dibenzofurans (PCDFs) based on quantitative structure–property relationships (QSPRs) for the subcooled liquid vaporization enthalpy and entropy in terms of simple molecular structure descriptors and the system temperature. It turned out that subcooled liquid vaporization enthalpies and entropies for these compound classes can be estimated from the number of carbon atoms, the number of chlorine atoms, the number of PCB ortho-chlorine atoms and the system temperature. Subcooled liquid vapor pressures at 298 K calculated from the estimated vaporization enthalpies and entropies were equal to directly measured experimental values as well as to experimental values determined by gas chromatographic methods within, on average, 0.15 and 0.12–0.3 log units, respectively.

Conformational changes and S 1 ← S 0 origin transition energies: Polychlorinated biphenyls (PCBs)

Geometries and S 1 ← S 0 origin transition energies for biphenyl, deuterated biphenyl, and 24 PCBs were obtained using a Hartree-Fock (HF), a single-excitation configuration interaction (CIS), and a related CI method with doubles correction (CIS(D)). The HF and CIS geometries for biphenyl are in fairly good agreement with those obtained by a complete active space self-consistent field (CASSCF) method. Calculated results show that, in both S 0 and S 1 states of PCBs, the torsional angles and the inter-ring bond lengths can be classified according to the number of ortho-chlorine atoms, n o-Cl . This suggests that the difference in electronic energy between the S 0 and the S 1 state also can be specified by n o-Cl . The HF and CIS energies were corrected for electron correlation on the assumption that the electron correlation energy can be partitioned into constituent contributions. Calculated S 1 ← S 0 origin transition energies agree with experimental values within an error of 2%. This level of accuracy is comparable to that of the S 1 ← S 0 origin transition energy for biphenyl calculated using the CASSCF method. The correction for electron correlation energy is largely due to contributions of the parent molecule and ortho-chlorine atoms. The present results will facilitate the analysis of electronic spectra of PCBs.

Activation of chlorine and fluorine by a phenylazo group towards nucleophilic aromatic substitution. Regioselective preparation of polysubstituted anilines

A phenylazo group was used for selective activation of ortho fluorine and chlorine atoms towards nucleophilic aromatic substitution with the propanethiolate anion. This enabled a regioselective synthesis of three substituted 4-alkoxyanilines. The regioselectivity of substitution was confirmed by comparison of experimental NMR chemical shifts with empirically predicted values. The observed reactivity of the substrates is discussed in the context of the substituent effect.

Density functional theory study of conformations, barriers to internal rotations and torsional potentials of polychlorinated biphenyls

Torsional barriers, potential energy curves, structural parameters and vibrational frequencies were calculated for 119 polychlorinated biphenyls (PCBs) at the B3LYP/6-31G(d,p) density functional theory level. From these calculations, the molecular parameters of remaining 90 PCB congeners can be estimated with reasonable accuracy. The conformations and torsional barriers of PCBs are mainly determined by the number of ortho chlorine atoms, while the meta chlorine atoms have a small influence on the torsional angles and barriers. All 209 PCBs were sorted into 18 groups depending on the number of ortho and adjacent meta substituents. In each group the internal rotation behavior of PCB congeners is very similar. For PCBs with 2–4 ortho chlorine atoms, the calculated barrier heights are 10–80 kJ/mol higher than those determined earlier by semiempirical AM1 method.

Development of a high-performance liquid chromatography carbon column based method for the fractionation of dioxin-like polychlorinated biphenyls

A method to separate polychlorinated biphenyls (PCBs) by using high-performance liquid chromatography (HPLC) was developed. The HPLC column was packed with Amoco PX-21 activated carbon dispersed on octadecylsilane (ODS). The separation was carried out by gradient elution with n-hexane–dichloromethane and toluene in the forward direction followed by reversed elution with toluene. The results show that this HPLC method is useful for the separation of PCBs according to the number of substituted ortho chlorine atoms attached to the biphenyl structure. Average recoveries for a number of individual di- ortho PCBs, mono- ortho PCBs, and non- ortho PCBs in three selected elution windows were 97, 92, and 96%, respectively. Clophen A50, a herring sample, and a cod liver oil sample were fractionated on the column and the analytical results are compared with data from the literature. The method presented here is useful for quantitative separations of mono- ortho PCBs as well as non- ortho PCBs which have been assigned toxic equivalency factors by the World Health Organisation.

(β-Octafluoro-meso-tetraarylporphyrin)manganese Complexes: Synthesis, Characterization and Catalytic Behaviour in Monooxygenation Reactions

The synthesis and characterization of manganese complexes of β-octafluoro-meso-tetraarylporphyrins are reported. The presence of the electron-withdrawing β-fluorine atoms induces a very large shift of the redox potential for the oxidation of the manganese(II) derivatives. With the meso-aryl group bearing two ortho-chlorine atoms (2,6-dichlorophenyl) or five fluorine atoms (pentafluorophenyl), metal complexation leads to the isolation of pure manganese(II) compounds. The stability and catalytic activity of these new derivatives have been studied using hydrogen peroxide and iodosylbenzene as oxidants, and standard substrates for epoxidation and hydroxylation reactions. The results are compared to those obtained with the β-hydrogenated analogs under the same conditions. In the case of hydrogen peroxide, the high level of porphyrin degradation prevents efficient catalytic activity. With iodosylbenzene as oxidant, both stability and epoxidation are similar to those of the β-hydrogenated porphyrins, however, a substantial improvement in the efficiency of the hydroxylation of cyclohexane is observed with up to 33 turnovers with (perfluorotetraphenylporphyrin)manganese(II).

Removal of chlorinated phenols in upflow anaerobic sludge blanket reactors

The dechlorination of chlorophenol (CP) compounds was investigated using upflow anaerobic sludge blanket reactors. A total of five trichlorophenols (TCPs) and a single dichlorophenol (DCP) were individually treated: 2,3,4-TCP; 2,3,5-TCP; 2,3,6-TCP; 2,4,5-TCP; 2,4,6-TCP; and 3,5-DCP. Synthetic wastewater composed of sucrose and acetic acid provided an alternate, readily biodegradable carbon source. Each chlorinated compound was concurrently fed to separate reactors. The parameters that were quantified include biogas composition, acetic acid concentration, COD, and VSS. The degree to which CPs were sorbed to the granular biomass in actively dechlorinating UASB reactors was found to be insignificant. CP compounds were able to be metabolized to mineral end products to a large extent at loadings where reactor performance was not impaired. Ortho chlorine atoms were most readily removed from CPs. CPs containing chlorine atoms in the para position were the most toxic agents with 2,4,5-TCP being the most toxic compound. Toxicity was reversible.

Removal of chlorinated phenols in upflow anaerobic sludge blanket reactors

The dechlorination of chlorophenol (CP) compounds was investigated using upflow anaerobic sludge blanket reactors. A total of five trichlorophenols (TCPs) and a single dichlorophenol (DCP) were individually treated: 2,3,4-TCP; 2,3,5-TCP; 2,3,6-TCP; 2,4,5-TCP; 2,4,6-TCP; and 3,5-DCP. Synthetic wastewater composed of sucrose and acetic acid provided an alternate, readily biodegradable carbon source. Each chlorinated compound was concurrently fed to separate reactors. The parameters that were quantified include biogas composition, acetic acid concentration, COD, and VSS. The degree to which CPs were sorbed to the granular biomass in actively dechlorinating UASB reactors was found to be insignificant. CP compounds were able to be metabolized to mineral end products to a large extent at loadings where reactor performance was not impaired. Ortho chlorine atoms were most readily removed from CPs. CPs containing chlorine atoms in the para position were the most toxic agents with 2,4,5-TCP being the most toxic compound. Toxicity was reversible.

Measurements of Octanol−Air Partition Coefficients for Polychlorinated Biphenyls

The octanol−air partition coefficient, KOA, is measured for 15 polychlorinated biphenyls (PCBs) over the temperature range −10 °C to +30 °C using a generator column method. The enthalpy of phase change from octanol to air, H, is calculated for 18 PCBs and ranges from 66 to 90 kJ/mol. Enthalpy of dissolution of the liquid phase PCB in octanol, ΔSOLH, calculated as ΔVAPH − H, has a mean value of 6.6 kJ/mol (n = 18) and there is no correlation of ΔSOLH with homolog group or number of ortho-substituted chlorine atoms. Results show that KOA values increase within a homolog group for congeners having fewer ortho chlorine atoms. A log10 − log10 correlation of KOA against liquid-phase vapor pressure (poL) shows enhanced partitioning into octanol for mono- and non-ortho congeners. Separate regressions for non/mono-ortho and multi-ortho groups allow KOA to be estimated for other congeners.

The SNAr Reaction of 2,3,5,6-Tetrachloronitrobenzene with Diamines under High Pressure: Formation of Cyclization Products

Abstract The reaction of 2,3,5,6-tetrachloronitrobenzene with ethylenediamine under high pressure gave mainly a 1 : 1-product and a bridged 2 : 1-product by the substitution of a nitro group and/or an o-chlorine atom. The ratio of the products varied depending upon the amount of amine used. Other diamines, such as 1,4-butanediamine cis-and trans-1,2-cyclohexanediamines, m-xylylenediamine, and o-phenylenediamine, gave similar results. On the other hand, N,N′-dimethylethylenediamine and N,N′-dimethyl-1,3-propanediamine gave cyclization products through successive substitutions of an ortho-chlorine atom and a nitro group by the two methylamino groups of a molecule of diamine. N-Methylethylenediamine afforded a 1 : 1-product through the substitution of a nitro group by a primary amino group together with a cyclic 1 : 1-product through substitutions of an o-chlorine atom and a nitro group by secondary and primary amino groups, respectively.

Correlation between electron capture negative chemical ionization mass spectrometric fragmentation and calculated internal energies for polychlorinated biphenyls

Correlations between molecular structure and fragmentation observed in electron capture negative chemical ionization mass spectra (moderator gas = methane) of 49 selected tetrachlorinated, pentachlorinated, and hexachlorinated biphenyls have been investigated by using molecular modeling. The semiempirical general molecular orbital program MOPAC was used to calculate molecular properties for biphenyl and the 209 polychlorinated biphenyls. The mass spectrometric ionization and fragmentation processes were found to be linked to the number of chlorine atoms present on the biphenyl, and to the number of those chlorine atoms in the ortho (2, 2′, 6, and 6′) positions. The intensity of molecular ions increased with the number of chlorine atoms present, but this was counteracted by enhanced fragmentation as the number of ortho position chlorine atoms increased. The molecular parameters that were most closely linked with the number of ortho chlorine atoms were the twist angle between the phenyl rings and the energy of the lowest unoccupied molecular orbital (LUMO). It is suggested that fragmentation occurs when the energy of the ionizing electron exceeds the energy difference between the LUMO and LUMO + 1 orbitals.

Review: Biological Activity, Determination and Occurrence of Planar, Mono- and Di-Ortho PCBs

Abstract Some of the 209 polychlorinated biphenyls (PCBs) are stereochemically similar to the planar 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and, because of this similarity, exert biochemical activity and toxicity comparable to that of TCDD. The molecular dimensions and the planarity of the PCB molecule appear to be important for the interaction with the TCDD receptor. These structural requirements, in turn depend on the number of ortho chlorine atoms and the presence of two para and at least two meta chlorine atoms on the biphenyl skeleton. Planar PCBs (i.e., without ortho chlorines), their mono- and some of their di-ortho substituted congeners have inductive properties similar to 3-methylcholanthrene- or mixed-type induction of mixed-function oxidases. These congeners also appear to have the greatest toxic potential. Planar PCBs and some of their mono- and di-ortho substituted congeners occur in very low concentrations in commercial PCB mixtures. Hence, their environmental occurrence is relatively lo...

Chlorinated organic derivatives containing MoHg and WHg bonds: Importance of the steric effects in their stabilization

A series of MoHg and WHg bonded complexes [RHgM(CO) 3Cp], (R = 2,4,6-C 6H 2Cl 3,2,3,5,6-C 6,HCl 4 and C 6Cl 5) have been prepared from ClHgR and the salts Na[M(CO) 3)Cp]. When R contains only one ortho chlorine atom (R = 2,5-C 6H 3Cl 2, 2,3,4-C 6H 2Cl 3 and 2,3,4,5-C 6HCl 4) a symmetrisation process occurs to give the corresponding HgR 2 and Hg[M(CO) 3Cp) 22. These results indicate that steric effects are very important in the formation of compounds containing molybdenum- or tungsten—mercury bonds. Complexes of the type [(C 6Cl 5)HgM(CO) 2(PPh 3)Cp] (M = Mo and W) are obtained from [(C 6Cl 5)HgM(CO) 3Cp] and PPh 3 in boiling ethanol.

Structure-Activity Relationships of Sulfonamide Drugs and Human Carbonic Anhydrase C: Modeling of Inhibitor Molecules into the Receptor Site of the Enzyme with an Interactive Computer Graphics Display

We have analyzed the molecular interaction of 28 sulfonamide inhibitors with human carbonic anhydrase C (HCAC) using an interactive computer graphic display. Small aromatic sulfonamides gain most of their inhibitory power towards HCAC from the interaction of hydrogen bond acceptors at the para or meta positions with hydrophilic residues of the enzyme. Additional coordinated water molecules stabilize the complexes of heterocyclic sulfonamides (i.e., thiophenes, 1,3-thiazoles, and 1,3,4-thiadiazoles) with HCAC. We propose two different modes of binding of the heterocyclic ring with respect to the active site cleft: the heterocyclic sulfur atom of a 3,4-unsubstituted thiophene approaches the oxygen atom of a coordinated water molecule (sulfur “out”), whereas in 3,4-unsubstituted 1,3,4-thiadiazoles, the sulfur is in contact with a hydrophobic part of the receptor site (sulfur “in”). This proposal is consistent with crystallographic evidence. Sulfonamides with two aromatic or heterocyclic rings also interact with a hydrophobic pocket of the enzyme located >10 Å away from the active site metal Zn2+. We also discuss the possibility that the relative inactivity of thiazide diuretics is due to the steric interaction of the ortho chlorine atom with the enzyme receptor cavity.