Chloro Compounds Research Articles

Further studies of tetrakis( N, N′-dialkylbenzamidinato)diruthenium(III) chloro and alkynyl compounds: molecular engineering of metallayne monomers

Three diruthenium(III) compounds Ru 2( L) 4Cl 2, where L is mMeODMBA ( N, N′-dimethyl-3-methoxybenzamidinate, 1a), DiMeODMBA ( N, N′-dimethyl-3,5-dimethoxy benzamidinate, 1b), or DEBA ( N, N′-diethylbenzamidinate, 1c), were prepared from the reactions between Ru 2(OAc) 4Cl and respective H L under reflux conditions. Metathesis reactions between 1 and LiC 2Y resulted in bis-alkynyl derivatives Ru 2( L) 4(C 2Y) 2 [Y=Ph ( 2), SiMe 3 ( 3), Si i Pr 3 ( 4) and C 2SiMe 3 ( 5)]. The parent compounds 1 are paramagnetic ( S=1), while bis-alkynyl derivatives 2– 5 are diamagnetic and display well-solved 1H- and 13C-NMR spectra. Molecular structures of compounds 1b, 1c, 2c, 3c and 4b were established through single crystal X-ray diffraction studies, which revealed RuRu bond lengths of ca. 2.32 Å for parent compounds 1 and 2.45 Å for bis-alkynyl derivatives. Cyclic voltammograms of all compounds feature three one-electron couples: an oxidation and two reductions, while the reversibility of observed couples depends on the nature of axial ligands.

Pd(II) and Pt(II) complexes of 2,2′-biimidazole and its N, N′-dimethyl derivative. The crystal structure of [{PtBr(DMSO)} 2(Me 2bim)] (Me 2bim= N, N′-dimethyl-2,2′-biimidazole)

The complexes [PdCl 2(LL)] and [PtX 2(LL)] [X=Cl, Br or I; LL=2,2′-biimidazole (H 2bim) or N, N′-dimethyl-2,2′-biimidazole (Me 2bim)] were prepared and characterized spectroscopically. The effects of the chloro compounds on plasmid DNA conformation were studied by electrophoresis in agarose gels, and that of [PtCl 2(H 2bim)] on calf thymus DNA by circular dichroism spectroscopy. The observation that these effects were adversely affected by addition of DMSO (originally used with [PtCl 2(Me 2bim)], to improve its solubility) prompted a study of the solvolysis of [PtCl 2(H 2bim)] by this solvent. 1H and 195Pt NMR, and electrospray mass spectra, showed the solvolysis of both PtCl and PtN bonds, the release of the ligand H 2bim, and the formation of several polynuclear species. X-ray diffractometry of the dinuclear Pt(I) compound [{PtBr(DMSO)} 2(Me 2bim)] showed the ligand Me 2bim to bridge through its non-methylated N atoms between two platinum atoms, the coordination spheres of which were each completed by a Br − ligand, the S atom of a DMSO molecule, and the other Pt atom; the PtPt bond is 2.5560(9) Å in length.

Photochemical activity of organic compounds in ice induced by sunlight irradiation: The Svalbard project

[1] Field experiments in Ny-Ålesund, Spitsbergen Island (Svalbard) demonstrated that water ice can be a suitable reaction medium for photochemical transformations of organic pollutants. Several aromatic carbonyl, chloro, nitro or hydroxy compounds, frozen in the ice-matrix samples, underwent very efficient sunlight-induced chemical changes. The photoproducts, in many cases completely different from those obtained from liquid solution photolysis, might pose a high toxicological risk to biota when they enter the environment. It is concluded that the results could be applicable to natural snow and ice, and that possible photochemical transformations should be considered in the ice-core record studies.

Semiconducting perovskites (2-XC6H4C2H4NH3)2SnI4 (X = F, Cl, Br): steric interaction between the organic and inorganic layers.

Two new semiconducting hybrid perovskites based on 2-substituted phenethylammonium cations, (2-XC(6)H(4)C(2)H(4)NH(3))(2)SnI(4) (X = Br, Cl), are characterized and compared with the previously reported X = F compound, with a focus on the steric interaction between the organic and inorganic components. The crystal structure of (2-ClC(6)H(4)C(2)H(4)NH(3))(2)SnI(4) is solved in a disordered subcell [C2/m, a = 33.781(7) A, b = 6.178(1) A, c = 6.190(1) A, beta = 90.42(3)(o), and Z = 2]. The structure is similar to the known (2-FC(6)H(4)C(2)H(4)NH(3))(2)SnI(4) structure with regard to both the conformation of the organic cations and the bonding features of the inorganic sheet. The (2-BrC(6)H(4)C(2)H(4)NH(3))(2)SnI(4) system adopts a fully ordered monoclinic cell [P2(1)/c, a = 18.540(2) A, b = 8.3443(7) A, c = 8.7795(7) A, beta = 93.039(1)(o), and Z = 2]. The organic cation adopts the anti conformation, instead of the gauche conformation observed in the X = F and Cl compounds, apparently because of the need to accommodate the additional volume of the bromo group. The steric effect of the bromo group also impacts the perovskite sheet, causing notable distortions, such as a compressed Sn-I-Sn bond angle (148.7(o), as compared with the average values of 153.3 and 154.8(o) for the fluoro and chloro compounds, respectively). The optical absorption features a substantial blue shift (lowest exciton peak: 557 nm, 2.23 eV) relative to the spectra of the fluoro and chloro compounds (588 and 586 nm, respectively). Also presented are transport properties for thin-film field-effect transistors (TFTs) based on spin-coated films of the two hybrid semiconductors.

Conformational analysis of 2-halocyclohexanones: an NMR, theoretical and solvation study

The conformational equilibria of 2-fluoro-, 2-chloro- and 2-iodo-cyclohexanone have been determined in various solvents by measurement of the J2–3 couplings. The observed couplings were analysed using theoretical and solvation calculations to give both the conformer energies in the solvents studied plus the vapour phase energies and the coupling constants in the distinct conformers. These plus previous results for the 2-bromo compound give the conformer energies and couplings of all the 2-halocyclohexanones. In the 2-fluoro compound the axial conformation is the most stable one in the vapour phase (Eeq − Eax = 0.45 kcal mol−1), while the equatorial conformer predominates in all the solvents studied. The other haloketones show similar behaviour, but the energy difference in the vapour phase is larger (Eeq − Eax = 1.05, 1.50 and 1.90 kcal mol−1, for the chloro, bromo and iodo compounds respectively) and the axial conformer is still the prevailing conformer in CCl4 solution for the chloro and bromo ketones and is the major form in all solvents for the iodo compound. The vapour state conformer energies for the fluoro and chloro compounds are in complete agreement with the ab initio calculated energies, but those for the bromo and iodo are not in such good agreement. Both the ab initio calculations and molecular mechanics are used to discuss the origins of the conformer energies. It is shown that the interaction between the C2 halogen and the CO oxygen in the equatorial conformer is strongly attractive for fluorine, much less so for chlorine, ca. zero for bromine and repulsive for iodine. Comparison of the conformer couplings obtained here with calculated values show generally good agreement.

Structural basis for intumescence– study of model compounds containing spiro phosphorus moiety and polymers containing such units

Spiro phosphorus compounds play a vital role, in recent years, in imparting flame retardancy and intumescence to the polymers. To ascertain the mechanism of the intumescency, model spiro phosphorus compounds, i.e., 3,9-disubstituted-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5.5]-undecan- 3,9-dioxide, were chosen (compound I : substitution is chloro group and compound II : substitution is hydroxo group). The model compounds were investigated using Differential Thermal Analysis (DTA) and Thermal Volatilization Analysis (TVA), Vacuum Pyrolysis-MS and Off-line Pyrolysis followed by degradation product analysis by GC-MS. Dichlorospiro compound (I) showed an eruptive release of gases at 320°C and dihydroxo spiro compound (II) at about 350°C. The major components of the gas released were found to be HCl and H2O in the case of compound I and H2O in the case of compound II. The degradation product analysis showed the formation of wide varieties of substituted and condensed aromatic compounds in measurable quantities. From the acquired data, it is confirmed that the intumescence takes place within a narrow range of temperature (10°) and in this temperature limit extensive dehydrohalogenation and dehydration are taking place. Highly thermally reactive unsaturated hydrocarbons are produced which mainly undergo polymerization to aromatic compounds and finally to char.

Photocyclization of 3-styrylcyclohex-2-enones to 2,3-dihydro-1H-phenanthren-4-ones

Styrylcyclohex-2-enones (3a-d) are cyclized photochemically to 2,3-dihydro-1H-phenanthren- 4-ones (4a-d). The corresponding phenanthren-4-ones with a methoxy group at C-5 (opposing the carbonyl at C-4) are not formed. The starting material 3a was prepared employing a Heck reaction of the styrenes 1a with 5,5- dimethyl-3-chlorocyclohex-2-enone (2a) and 5,5-dimethyl-3-bromocyclohex-2-enone (2b) (Scheme 1). Since both of the halides afforded the dienone 3a in good yield, the more easily available chloro compound 2a was used in the subsequent preparation of 3b-e starting from the styrenes 1b-e. The crystalline dienones had the E configuration as deduced from the coupling

Synthesis and Characterisation of Bis-azido Methyl Oxetane and its Polymer and Copolymer with Tetrahydrofuran

Bis-azido methyl oxetane (BAMO) was synthesised from pentaerythritol in two steps. Pentaerythritol was chlorinated to yield a mixture of mono, di, tri and tetra chloro compounds. The trichloro compound on ring closure gives bis-chloro methyl oxetane (BCMO). It was reacted with sodium azide in aqueous medium to obtain BAMO. The latter was polymerised using BF3 etherate catalyst and 1,4-butanediol initiator. Similarly, the BAMO- THF copolymer was also synthesised. All the monomers and polymers were characterised by IR, 1H-NMR, 13C-NMR, and refractive index. The polymers were also characterised for molecular weight, hydroxyl value, etc. Thermal analysis showed that both polymers degrade exothermically with T max of 237 °C for poly BAMO and 241°C for BAMO- THF copolymer with activation energy of 39 kcal/mol and 40 kcal/mol, respectively. Explosive properties like impact and friction sensitivity of BAMO and the other polymers were also determined.

A 1H NMR and molecular modelling investigation of diastereotopic methylene hydrogen atoms

AbstractThe 1H NMR spectra of methyl 3‐bromo‐2‐methylpropionate (1a) and the corresponding chloro compound (2a) show no long‐range coupling between the methyl and methylene protons. In contrast, in the analogous dihalocompounds, methyl 2,3‐dibromo‐2‐methylpropionate (1b) and methyl 2,3‐dichloro‐2‐methylpropionate (2b), one of the methylene protons exhibits a large 4JHH coupling (0.8 Hz) to the methyl group, but the other proton shows no observable splitting. This can be explained quantitatively by calculations of the conformational preferences in these compounds combined with the known orientation dependence of the 4JHHcouplings. One conformer predominates in the dihalo compounds 1b and 2b, and this is responsible for the 4JHH coupling. In 1a and 2a all three conformers are populated and the 4JHH couplings average to zero. The technique is a potentially general method of unambiguously assigning diastereotopic methylene protons. Copyright © 2002 John Wiley & Sons, Ltd.

Synthesis and Structure of Azobenzenes Bearing Silyl, Germyl, and Stannyl Groups at 2-Position

Abstract Azobenzenes, 2-R12R2MC6H4N=NPh (M = Si (1a–c), Ge (7), and Sn (8)), were synthesized by reactions of 2-lithioazobenzene (6) with the corresponding chloro compounds, R12R2MCl, respectively, in good to moderate yields. The crystal structure of 1c was established by the X-ray crystallographic analysis.

5-Chloro- and 5-bromobenzfurazan 1-oxide revisited

At room temperature the two title compounds are isomorphous. Both have a disordered structure that includes a major component, one of the title compounds, and a minor component, the 6-halo isomer, occurring at the same site in the crystal. When the chloro compound is cooled to as low as 98 K, there is no change in the structure and no significant change in the degree of disorder. When the bromo compound is cooled, it undergoes a second-order phase transition at 282 K to a second polymorph, structurally very similar, but with two molecules in the asymmetric unit. In both isomorphs and both polymorphs the molecules occur in two-dimensional layers that are essentially the same. In the low-temperature form of the bromo compound the layers have shifted relative to each other by approximately 0.7 A in y. In the low-temperature form the disorder, which is still present after the transition, decreases as the temperature is lowered.

Synthesis and Structure of Os~5(mu-Cl)~2(CO)~1~6(CNBu^t)~2: A Cluster with a "Hook" Arrangement of Metal Atoms

Os5(μ-X)2(CO)16(L)2 (X=Cl, 1, Br; L=CNBut) clusters have been prepared by the reaction of Os3(μ-X)2(CO)10 with Os(CO)4(L) at a 1:2 molar ratio in solution at 60°C. The crystal structure of the chloro compound reveals that the Os3(μ-Cl)2 fragment present in the precursory cluster is maintained in 1 with a coordination site cis to the Cl ligands occupied by the unusual Os(CO)4Os(CO)3(L)2 unit. The resulting “hook” arrangement of the Os5 skeleton has not been observed previously. The OsOs lengths are in the range 2.8384(6)–2.8999(6)A. The OsOs bonds associated with the pendant fragment are both considered dative bonds.

In vivo incorporation of radioactive 36Cl, a method for monitoring chloro compounds in biological material

A new method for fast and easy monitoring of the presence, isolation, and separation of natural chloro compounds in plants is described. The method relies on the in vivo incorporation of radioactive 36Cl and new enhancement methods in autoradiographic technology. The method allows the time of exposure to be limited to 4 days and is thus suitable for routine purposes.

Isomorphism and pseudosymmetry in 2,6-dichloro- and 2, 6-dibromobenzonitrile.

The title compounds are isomorphous, with two half-molecules in the asymmetric unit of a monoclinic unit cell in the space group C2/m. For the chloro compound: a = 18.0525 (8), b = 20.7374 (10), c = 3. 8334 (2) A, beta = 101.143 (1) degrees; for the bromo compound: a = 18.2269 (15), b = 21.349 (2), c = 3.9663 (3) A, beta = 101.446 (2) degrees. The dominant intermolecular interactions are between halogen atoms rather than between halogen and nitrile, as is the case in the corresponding 2,4,6-trihalobenzonitriles. The molecules pack into layers with a fourfold pseudosymmetry. The pseudosymmetry appears to be the consequence of halogen-halogen intermolecular interactions.

SYNTHESIS OF POLY(METHYLENE TEREPHTHALATE) AND COPOLYMERS WITH POLY(ETHYLENE TEREPHTHALATE)

Poly(methylene terephthalate) (PMT) and poly(ethylene terephthalate) (PET) were synthesized by triethylamine-mediated reactions of terephthalic acid and dihalomethanes or 1,2-dihaloethanes, respectively. Reactions with chloro compounds required longer reaction times and higher temper-atures than those with bromo. Copolymers were synthesized by using proportionate amounts of dihalomethane/1,2-dihaloethane mixtures. Copolymer compositions were determined by inte-grations of relative areas of methylene and ethylene 1H NMR peaks. Mn values were determined from 1H NMR end group signals. Mole fraction feed is linearly related to CH2/CH2CH2 incorporation into copolymer products. Mechanisms are proposed to explain results.

N-(Halogendimethylsilyl)-1 -methylphospholanimine/N-(Halogenodimethylsilyl)-1 -methylphospholane Imines

N-Trimethylsilyl-1 -methylphospholane imine has been prepared by the Staudinger reaction of 1-methylphospholane with trimethylsilyl azide. Transsilylation reactions of the phosphine imine with dichloro or dibromodimethylsilane lead to dimeric N-(halogenodimethylsilyl)-l-methylphospholane imines with an ionic type of structure, containing a dicationic four-membered Si-N ring system. Upon heating, the chloro compound undergoes a reversible isomerization to give the corresponding covalent monomer.

Synthesis and Some Reactions of Quinoxalinecarboazides

AbstractChlorination of ethyl(quinoxalin‐2(1H)one)‐3‐carboxylate 1 gave ethyl (2‐chloroquinoxaline)‐3‐carboxylate 2;thionation of 1 by P2S5 or 2 by thiourea yielded the same product 3. Reaction of chloro compound 2 or thiocompound 3 with hydrazine hydrate gave pyrazolylquinoxaline 4. The reaction of ester 1 with thiourea or hydrazine hydrate afforded pyrimido quinoxaline 5 or carbohydrazide 6; the reaction of 6 with carbon disulfide in basic medium followed by alkylation afforded oxadiazoloquinoxaline derivatives 7, 8a,b. Carboazide 9 was produced by reaction of 5 with nitrous acid. Compound 9 on heating in an inert solvent, with or without amines, in alcohols or hydrolysis in H2O undergoes Curtius rearrangments to yield 10‐13. Reaction of 13 with thiosemicarbazide gave triazoloquinoxaline 14 which on reaction with alkylhalides or hydrazine hydrate yielded 15a‐c while hydrolysis of 13 gave 3‐aminoquinoxalinone 16 which was used as an intermediate to produce 17‐20.

Roles of chloro compound in homogeneous [Cr(2-ethylhexanoate) 3/2,5-dimethylpyrrole/triethylaluminum/chloro compound] catalyst system for ethylene trimerization

The effects of chloro compounds on the catalytic performance in ethylene trimerization reactions were studied using a homogeneous [Cr(2-ethylhexanoate) 3/2,5-dimethylpyrrole (DMP)/triethylaluminum (TEA)/chloro compound] catalyst system. Chloro compounds of different types showed a broad range of effects on the performance of the catalytic system. The chloro compounds of geminal chloro groups greatly improved the catalytic activity and 1-hexene selectivity of ethylene trimerization reaction. Some specific interaction modes of chloro groups with dimeric TEA and active Cr species in the catalytic cycle were proposed to explain the catalytic activity and 1-hexene selectivity improvement effects of chloro compound in the ethylene trimerization reaction.

Hydrogen Isotope Effects in Electrochemical Reductions of Organic Chloro Compounds

The kinetic hydrogen isotope effects in electrochemical reductions of CCl3COOD, CDCl2COOD, CCl4, CDCl3, benzyl chloride, 1-chloronaphthalene and 4-chlorobenzonitrile in deuterated reaction media were determined. The aliphatic chloro compounds are reduced with rather small isotope effects kH/kD = 1.2…1.7, as expected if anionic intermediates are formed and protonated. Benzyl chloride is reduced with an apparent kH/kD = 2.1, which is probably too high due to radical reactions. Aromatic chloro compounds are reduced with significant participation of a second mechanism via radical intermediates which abstract carbon-bound hydrogen atoms from the components of the reaction system. The resulting isotope effects are kH/kD = 1.2 for the part of the reduction which proceeds via anions and kH/kD ∼ 2.5 for the competing radical reaction.

Electrophilic Substitution of 1,1,2,2,9,9,10,10-Octafluoro[2.2]paracyclophane

Nitration of octafluoro[2.2]paracyclophane (OFP) provides an entry into the synthesis of a series of 11 monosubstituted OFPs, including the nitro, amino, chloro, bromo, iodo, hydroxy, and trifluoromethyl compounds. The NMR, mass spectrometric, and UV spectral properties of all of these derivatives are presented and discussed, and they are compared with those of its hydrocarbon analogue, [2.2]paracyclophane.