Influence Of Chlorine Substituents Research Articles

Enantioseparation of three isomeric α-(chlorophenyl)propanoic acid by countercurrent chromatography and investigation of chlorine substituent through characterization of inclusion interaction

The influence of chlorine substituents in chiral separation of three racemic 2-(chlorophenyl)propanoic acids by countercurrent chromatography using hydroxypropyl-β-cyclodextrin as a chiral additive were mainly investigated in the present paper, including 2-(2-chlorophenyl)propanoic acids, 2-(3-chlorophenyl)propanoic acids and 2-(4-chlorophenyl)propanoic acids. The influences of chromatographic conditions on the retention behavior were studied by enantioselective liquid-liquid extraction experiments using the methodology of response surface It was found that 2-(3-chlorophenyl)propanoic acids could be successfully chiral separated by countercurrent chromatography, while no resolution was achieved for racemic 2-(2-chlorophenyl)propanoic acids and 2-(4-chlorophenyl)propanoic acids under optimized separation conditions. The formation of 1:1 stoichiometric inclusion compounds between 2-(3-chlorophenyl)propanoic acids and HP-β-CD was determined by UV spectra measurements. The inclusion constants for 2-(3-chlorophenyl)propanoic acids and HP-β-CD were determined by the Benesi-Hildebrand equation. Meanwhile, the inclusion constants of 2-(3-chlorophenyl)-propanoic acid enantiomer and HP-β-CD were obtained by the pesudophase retention equation in countercurrent chromatography. Furthermore, the inclusion interactions of the three racemates with HP-β-CD were also investigated by the molecular docking. The results obtained from UV spectra measurements and molecular docking showed that the racemate with chlorine substituents in meta-position presented the highest enantiorecognition while the racemates with chlorine substituents in ortho-position had the lowest enantiorecognition. The above results further indicated that forming a stable inclusion complex between racemate and chiral selector is a prerequisite for a successful enantioseparation and at the same time, the difference in inclusion capacity between the two enantiomers is also essential for the enantioseparation.

Influence of chlorine substituents on the aggregation behavior of chlorobenzoyl-substituted ferrocene derivates

The influence of chlorine substituents on the molecular arrangement in the solid state of chlorinated benzoyl-ferrocene derivates with restricted molecular flexibility was investigated by crystal structure determinations and theoretical calculations. Four different chlorinated benzoyl-ferrocene derivates were crystallized from a saturated CHCl3 solution and analyzed by X-ray diffraction. Under consideration of the structural restrictions, a comparable trend of rearrangement in the crystal organization with increasing number of chlorine atoms is observed, which is analogous to findings for chlorine-substituted benzenes. More important, the molecules arrange in layers (1 and 4) and columns (2 and 3) and in all cases with repulsively orientated CF3···CF3 substituents. In addition, Cl···Cl interactions are visible in 1 (type I) and 4 (type II). Furthermore, the crystal packing motifs were also analyzed based on ab initio quantum-chemical calculations of the intermolecular interaction energy, using the B97-D3/def2-TZVP method. According to the topology of intermolecular interaction, the crystal structures have either columnar or layered structure depending on the presence of Cl substituent in para-position of benzene ring. It was also found that Cl···Cl interactions play a secondary role in crystal organization, and the substituent effect is maybe due to polarization of the aromatic ring, which leads ultimately to an increase in the energy of stacking interactions between the aryl substituents. Analysis of the crystal structures of chlorine substituents on the molecular arrangement in the solid state of restricted molecular flexible chlorinated benzoyl-ferrocene derivates shows a trend of rearrangement in the crystal organization with increasing number of chlorine atoms.

Grafting trimethylaluminum and its halogen derivatives on silica: general trends for (27)Al SS-NMR response from first principles calculations.

(27)Al NMR is the method of choice for studying grafted Al species on a large area solid support, such as co-catalysts for α-olefin oligomerization involving mesoporous silica materials. Here, we show how to interpret the (27)Al solid-state NMR spectrum and parameters for various types of Al monomeric and dimeric alkyl and halogen compounds grafted on silica, based on the trends obtained from first-principles calculations. Since most alkylaluminum species tend to form dimers in the gas phase, we chose as prototypes both the AlMe3 monomer and the Al2Me6 dimer. On top of that the influence of chlorine substituents on the NMR parameters is explored considering all possible isomers. There are two main effects on the Al NMR parameters observed in the case of monomers: (i) the larger π-donating character of the ligands (from Me to Cl for example) leads to a decrease of the quadrupolar coupling constant CQ and (ii) the larger σ-attracting character of the ligand (from Cl to F for example) yields an upfield variation of the Al chemical shift δISO while in contrast CQ is increased. The same is true also in the case of dimeric species, with an additional specific effect. By (27)Al solid state NMR we can differentiate clearly between terminal and bridge positions for the substituents. The reason for this phenomenon is explained in terms of different natural localized MO (NLMO) contributions to the CQ parameter. This aspect is important because the surface sites for this type of system are expected to be mostly dinuclear Al species, grafted on the silica surface via either two terminal or two bridging siloxy ligands.

Influence of chlorine substituents on rates of oxidation of chlorinated biphenyls by the biphenyl dioxygenase of Burkholderia sp. strain LB400.

Biphenyl dioxygenase from Burkholderia (Pseudomonas) sp. strain LB400 catalyzes the first reaction of a pathway for the degradation of biphenyl and a broad range of chlorinated biphenyls (CBs). The effect of chlorine substituents on catalysis was determined by measuring the specific activity of the enzyme with biphenyl and 18 congeners. The catalytic oxygenase component was purified and incubated with individual CBs in the presence of electron transport proteins and cofactors that were required for enzyme activity. The rate of depletion of biphenyl from the assay mixture and the rate of formation of cis-biphenyl 2,3-dihydrodiol, the oxidation product, were almost equal, indicating that the assay accurately measured enzyme-specific activity. Four classes of CBs were defined based on their oxidation rates. Class I contained 3-CB and 2,5-CB, which gave rates that were approximately twice that of biphenyl. Class II contained 2,5,3',4'-CB, 2,3,2',5'-CB, 2,3,4,5-CB, 2,3,2',3'-CB, 2,4, 5,2',5'-CB, 2,5,3'-CB, 2,5,4'-CB, 2-CB, and 3,4,5-CB, which gave rates that ranged from 97 to 35% of the biphenyl rate. Class III contained only 2,3,4,2',5'-CB, which gave a rate that was 4% of the biphenyl rate. Class IV contained 2,4,4'-CB, 2,4,2',4'-CB, 3,4,5, 2'-CB, 3,4,5,3'-CB, 3,5,3',5'-CB, and 3,4,5,2',5'-CB, which showed no detectable depletion. Rates were not significantly correlated with the aqueous solubilities of the CBs or the number of chlorine substituents on the rings. Oxidation products were detected for all class I, II, and III congeners and were identified as chlorinated cis-dihydrodiols for classes I and II. The specificity of biphenyl dioxygenase for the CBs examined in this study was determined by the relative positions of the chlorine substituents on the aromatic rings rather than the number of chlorine substituents on the rings.

‘Influence of chlorine substituents on biological activity of chemicals’: a comment

Pest Management ScienceVolume 56, Issue 1 p. 22-23 Comment ‘Influence of chlorine substituents on biological activity of chemicals’: a comment Michael D Turnbull, Corresponding Author Michael D Turnbull Mike.Turnbull@aguk.zeneca.com Zeneca Agrochemicals, Jealott's Hill International Research Station, Bracknell, Berks RG42 6ET, UKZeneca Agrochemicals, Jealott's Hill International Research Station, Bracknell, Berks RG42 6ET, UKSearch for more papers by this author Michael D Turnbull, Corresponding Author Michael D Turnbull Mike.Turnbull@aguk.zeneca.com Zeneca Agrochemicals, Jealott's Hill International Research Station, Bracknell, Berks RG42 6ET, UKZeneca Agrochemicals, Jealott's Hill International Research Station, Bracknell, Berks RG42 6ET, UKSearch for more papers by this author First published: 10 January 2000 https://doi.org/10.1002/(SICI)1526-4998(200001)56:1<22::AID-PS127>3.0.CO;2-IRead the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume56, Issue1January 2000Pages 22-23 RelatedInformation

?Influence of chlorine substituents on biological activity of chemicals?: a comment

Pest Management ScienceVolume 56, Issue 1 p. 22-23 Comment ‘Influence of chlorine substituents on biological activity of chemicals’: a comment Michael D Turnbull, Corresponding Author Michael D Turnbull Mike.Turnbull@aguk.zeneca.com Zeneca Agrochemicals, Jealott's Hill International Research Station, Bracknell, Berks RG42 6ET, UKZeneca Agrochemicals, Jealott's Hill International Research Station, Bracknell, Berks RG42 6ET, UKSearch for more papers by this author Michael D Turnbull, Corresponding Author Michael D Turnbull Mike.Turnbull@aguk.zeneca.com Zeneca Agrochemicals, Jealott's Hill International Research Station, Bracknell, Berks RG42 6ET, UKZeneca Agrochemicals, Jealott's Hill International Research Station, Bracknell, Berks RG42 6ET, UKSearch for more papers by this author First published: 10 January 2000 https://doi.org/10.1002/(SICI)1526-4998(200001)56:1<22::AID-PS127>3.0.CO;2-IRead the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume56, Issue1January 2000Pages 22-23 RelatedInformation

Influence of chlorine substituents on biological activity of chemicals: a review

Influence of chlorine substituents on biological activity of chemicals: a review

Influence of chlorine substituents on biological activity of chemicals: a review

A number of well known polychlorinated chemicals are toxicologically and environmentally unsafe. Because of their persistence they are in the focus of public discussions against chlorine chemistry. However, chlorinated organic chemicals in the molecular weight range between 200 and 600 constitute an important and indispensable segment in the arsenal of existing biologically active chemicals used as pharmaceuticals or crop-protection agents. Over the course of time it has been found empirically that the introduction of a chlorine atom into one or more specific positions of a biologically active molecule may substantially improve the intrinsic biological activity. In some cases the presence of a chlorine atom is crucial for significant activity in compounds derived both from nature and chemical synthesis. But in other cases chlorination diminishes or abolishes biological activity, as shown for chlordane homologues. Thus a chlorine atom, like any other substituent, is a modulator of activity. Almost all non-reactive chlorinated chemicals and chlorine-free chemicals are devoid of any biological activity at the highest concentration typically used in primary screening tests for discovery of useful biological properties. The influence of a substituent such as chlorine on the biological activity of a potential drug or crop protection agent still has to be established empirically in biological experiments designed to detect desired activity or toxicological properties. Sometimes chlorine does prove to be the optimum for improvement of activity. Long-term rigorous investigations of several hundred chlorinated compounds, registered by the authorities as pharmaceutical drugs or crop-protection agents, show that the generalisation ‘all chlorinated chemicals are dangerous’, deduced from the negative toxicological properties of a hundred chlorinated and reactive compounds of low molecular weight that are relevant in terms of safe working conditions in the chemical industry and for ecological safety, is not justified. Chlorinated compounds are not necessarily toxic or dangerous. Highly reactive chemicals or polychlorinated compounds cannot be compared with regard to toxicological properties with unreactive compounds having a low degree of chlorination. The chlorine atom, as one of many possible substituents used in synthetic organic chemistry, will remain in the future one of the important tools for probing structure–activity relationships in life science research and as a molecular component in commercialised compounds, in order to provide safer, more selective and more environmentally compatible products with higher activity for medicine and agriculture. © 1999 WILEY-VCH Verlag GmbH

Influence of chlorine substituents on biological activity of chemicals

A number of well known polychlorinated chemicals are toxicologically and environmentally unsafe. Because of their persistence they are in the focus of public discussions against chlorine chemistry. However, chlorinated organic chemicals in the molecular weight range between 200 and 600 constitute an important and indispensable segment in the arsenal of existing biologically active chemicals used as pharmaceuticals or crop protection agents. Over the course of time it has been found empirically that the introduction of a chlorine atom into one or more specific positions of a biologically active molecule may substantially improve the intrinsic biological activity. In some cases the presence of a chlorine atom is even crucial for significant activity of a compound derived from nature or chemical synthesis like in the diverse compounds 1 to 12 and 23 to 30. But in other cases chlorination diminishes or abolishes biological activity as shown for the chlordane homologues 139 to 143. Thus a chlorine atom, like any other substituent, is a modulator of activity as represented in the many examples 31 to 124. Almost all non-reactive chlorinated chemicals and chlorine-free chemicals are devoid of any biological activity at the highest concentration typically used in primary screening tests for discovery of useful biological properties. The influence of a substituent such as chlorine on the biological activity of a potential drug or crop protection agent still has to be established empirically in biological experiments designed to detect desired activity or toxicological properties. Sometimes chlorine does prove to be the optimum for improvement of activity. Long-term rigorous investigations of several hundred chlorinated compounds, registered by the authorities as pharmaceutical drugs or crop protection agents, show that the generalisation (“all chlorinated chemicals as a rule are dangerous”), deduced from the negative toxicological properties of a hundred chlorinated and reactive compounds of low molecular weight that are relevant in terms of safe working conditions in the chemical industry and for ecological safety, is not justified. Chlorinated compounds are not generally toxic or dangerous. Highly reactive chemicals or polychlorinated compounds can not be compared with regard to toxicological properties with unreactive compounds having a low degree of chlorination. The chlorine atom, as one of many possible substituents used in synthetic organic chemistry, will remain in the future one of the important tools for probing structure–activity relationships in life science research and as a molecular component in commercialised compounds, in order to provide safer, more selective and more environmentally compatible products with higher activity for medicine and agriculture.

Influence of chlorine substituents on biological activity of chemicals

A number of well known polychlorinated chemicals are toxicologically and environmentally unsafe. Because of their persistence they are in the focus of public discussions against chlorine chemistry. However, chlorinated organic chemicals in the molecular weight range between 200 and 600 constitute an important and indispensable segment in the arsenal of existing biologically active chemicals used as pharmaceuticals or crop protection agents. Over the course of time it has been found empirically that the introduction of a chlorine atom into one or more specific positions of a biologically active molecule may substantially improve the intrinsic biological activity. In some cases the presence of a chlorine atom is even crucial for significant activity of a compound derived from nature or chemical synthesis like in the diverse compounds 1 to 12 and 23 to 30. But in other cases chlorination diminishes or abolishes biological activity as shown for the chlordane homologues 139 to 143. Thus a chlorine atom, like any other substituent, is a modulator of activity as represented in the many examples 31 to 124. Almost all non-reactive chlorinated chemicals and chlorine-free chemicals are devoid of any biological activity at the highest concentration typically used in primary screening tests for discovery of useful biological properties. The influence of a substituent such as chlorine on the biological activity of a potential drug or crop protection agent still has to be established empirically in biological experiments designed to detect desired activity or toxicological properties. Sometimes chlorine does prove to be the optimum for improvement of activity. Long-term rigorous investigations of several hundred chlorinated compounds, registered by the authorities as pharmaceutical drugs or crop protection agents, show that the generalisation (“all chlorinated chemicals as a rule are dangerous”), deduced from the negative toxicological properties of a hundred chlorinated and reactive compounds of low molecular weight that are relevant in terms of safe working conditions in the chemical industry and for ecological safety, is not justified. Chlorinated compounds are not generally toxic or dangerous. Highly reactive chemicals or polychlorinated compounds can not be compared with regard to toxicological properties with unreactive compounds having a low degree of chlorination. The chlorine atom, as one of many possible substituents used in synthetic organic chemistry, will remain in the future one of the important tools for probing structure–activity relationships in life science research and as a molecular component in commercialised compounds, in order to provide safer, more selective and more environmentally compatible products with higher activity for medicine and agriculture.

ChemInform Abstract: BASIC ELIMINATION OF HCL FROM CHLORINATED ETHANES

Chloroethanes react with aqueous caustic to yield either elimination or substitution products. The reaction rates were measured for the dichloroethanes, trichloroethanes, tetrachloroethanes, and pentachloroethane between 283 and 353°K. The constants of HCl eleminations referring to the rate equation are given by all rate constants being in 1./mole·s and R in cal/mole· deg. With ethyl chloride, 1,1-dichloroethane, and 1,1,l-trichloroethane, the elimination is not observed and a slow substitution takes place. The influence of chlorine substituents on both sides of the molecule on mechanism and rate parameters is discussed.

Basic elimination of HCl from chlorinated ethanes

AbstractChloroethanes react with aqueous caustic to yield either elimination or substitution products. The reaction rates were measured for the dichloroethanes, trichloroethanes, tetrachloroethanes, and pentachloroethane between 283 and 353°K. The constants of HCl eleminations referring to the rate equation are given by all rate constants being in 1./mole·s and R in cal/mole· deg.With ethyl chloride, 1,1‐dichloroethane, and 1,1,l‐trichloroethane, the elimination is not observed and a slow substitution takes place. The influence of chlorine substituents on both sides of the molecule on mechanism and rate parameters is discussed.