Thermal,spectral and magnetic behaviour of 4-chloro-2-methoxybenzoates of light lanthanides(III)

4-Chloro-2-methoxybenzoates of light lanthanides(III) were obtained as mono-, di-or trihydrates with metal to ligand ratio of 1:3 and general formula Ln(C₈H₆ClO₃)₃·nH₂O, where n=1 for Ln=Ce, Pr, n=2 for Ln=Nd, Sm, Eu, Gd and n=3 for Ln=La. The complexes were characterized by elemental analysis, IR spectra, thermogravimetric studies, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate, chelating ligand. All complexes seem polycrystalline compounds. Their thermal stabilities were determined in air. When heated they dehydrate to form anhydrous salts which next are decomposed to the oxides of the respective metals. The solubilities of light lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10⁻⁵ mol dm⁻³. The magnetic moments were determined over the range of 77–300 K. They obey the Curie-Weiss law. The values of μ_eff calculated for all compounds are close to those obtained for Ln³⁺ by Hund and Van Vleck. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.     

Neighboring olefinic double-bond participation in gas phase pyrolysis of some alkenyl chlorides

4-Chloro-1-butene, 5-chloro-1-pentene, and 6-chloro-1-hexene have been shown to decompose, in a static system, mainly to hydrogen chloride and the corresponding alkadienes. In packed and unpacked clean Pyrex vessels the reactions were significantly heterogeneous. However, in a vessel seasoned with allyl bromide these reactions were homogeneous, unimolecular, and follow a first-order law. The working temperature range was 389.6–480.0°C and with a pressure range of 53–221 Torr. The rate constants for the homogeneous reactions were expressed by the following Arrhenius equations: 4-chloro-1-butene: logk(sec^?1) = (13.79 ± 0.17) – (223.8 ± 2.1)kJ/mole/2.303RT; 5-chloro-1-pentene: logk(sec^?1) = (14.25 ± 1.20) – (238.4 ± 12.7)kJ/mole/2.303RT; and 6-chloro-1-hexene: logk(sec^?1) = (12.38 ± 0.22) – (209.6 ± 2.9)kJ/mole/2.303RT. The olefinic double bond has been found to participate in the rate of dehydrohalogenation of 4-chloro-1-butene. The insulation of the CH₂?CH in chlorobutene by one or two methylene chains to the reaction center does not indicate neighboring group participation. The three-membered conformation is the most favored structure for anchimeric assistance of the double bond in gas phase pyrolysis of alkenyl chlorides. The heterolytic nature of these eliminations is also supported by the present work.     

In Situ Renewal of Working Surfaces of Solid Indicator Electrodes and Their Use in Electroanalysis

The design of a device for the rapid regeneration of the indicator electrode surface in a test solution is discussed. The results of testing this device are presented. The device allows obtaining reproducible areas and properties of the surfaces of solid indicator electrodes by mechanically cutting 0.1–5-μm surface layers. The best reproducibility of these parameters is attained when a hexanite-R cutter is used. The serviceability of the cutter is more than 10⁵ cuts. The high-quality renewal of electrode surfaces is achieved by cutting a 4– 5-μm layer of metallic (Pt, Ag, Au, Cu, Cd, Zn, Co, Ni, etc.) electrodes and a 0.1–1.5-μm layer of graphite and graphite-based electrodes. Optimum tool angles of the cutter for all types of solid electrodes are selected. Long-term tests of the developed technique for the mechanical renewal of electrode surface confirm that the electrode surface area is well reproducible in the series of 10⁴ measurements of the analytical signal (RSD = 0.2–0.6%). Examples are given that point to the enhancement of the electrochemical activity of the surfaces of some electrodes renewed in situ in a solution without their exposure to air. It is shown that the mechanical regeneration of the electrode surface in the solution is the main condition for depositing metals under high-voltage (up to 1000 V) conditions for electroaccumulation. The advantages of the proposed technique are exemplified by determining the concentrations of cations, anions, and some organic substances by direct and stripping voltammetry. __________ Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 12, 2005, pp. 1284–1295. Original Russian Text Copyright ? 2005 by Skvortsova, Aleksandrova, Tarasova, Kiryushov, Zamyatin.     

STRUCTURE OF METHYLPHEOPHORBIDE-RCI*

Abstract— The methanolic extract of the cyanobacterium (blue-green alga) Spirulina geitleri has been treated with methanolic acid to convert all chlorophyllous pigments to their methylpheophorbides. Fractionation of the latter from methylpheophorbide a by thin layer chromatography and high pressure liquid chromatography yielded methylpheophorbide-RCI. Its structure has been determined as 13²S-hydroxy-20-chloro-methylpheophorbide a by ¹H-nuclear magnetic resonance, absorption and circular dichroism spectroscopy, mass spectrometry and by partial synthesis from chlorophyll a. The pigment is isolated from Spirulina geitleri irrespective of the use or omission of chlorinated substances during the isolation procedure.     

Sorption-chromatographic determination of hydrazine and its substituted derivatives in air

Working conditions were found for the chemisorption preconcentration of hydrazine, phenylhydrazine, and 1,1-dimethylhydrazine from air with tubes containing silica gel with immobilized 4-chloro-5,7-dinitrobenzofurazan and the subsequent determination by high-performance liquid chromatography with diode array detection. A recovery of 98% (hydrazine), 90% (phenylhydrazine), and 97% (1,1-dimethylhydrazine) is attained at a thickness of the sorbent layer of 2 cm, an aspiration rate of 0.2–0.8 L/min, and a volume of aspirated air of 10 L. Silica gel with a particle size of 0.1–0.3 mm impregnated with 4-chloro-5,7-dinitrobenzofurazan (2 wt %) was used as the sorbent. The detection limits of compounds without regard for preconcentration after their desorption are 0.01 (hydrazine), 0.017 (1,1-dimethylhydrazine), and 0.015 mg/m³ (phenylhydrazine).     

Thermal, spectral and magnetic characterization of Co(II), Ni(II) AND Cu(II) 4-chloro-2-nitrobenzoates

Physico-chemical properties of 4-chloro-2-nitrobenzoates of Co(II), Ni(II), and Cu(II) were studied. The complexes were obtained as mono- and trihydrates with a metal ion to ligand ratio of 1:2. All analysed 4-chloro-2-nitrobenzoates are polycrystalline compounds with colours depending on the central ions: pink for Co(II), green for Ni(II), and blue for Cu(II) complexes. Their thermal decomposition was studied only in the range of 293–523 K, because it was found that on heating in air above 523 K 4-chloro-2-nitrobenzoates decompose explosively. Hydrated complexes lose crystallization water molecules in one step and anhydrous compounds are formed. The final products of their decomposition are the oxides of the respective transition metals. From the results it appears that during dehydration process no transformation of nitro group to nitrite takes place. The solubilities of analysed complexes in water at 293 K are of the order of 10^–4–10^–2 mol dm^–3. The magnetic moment values of Co²⁺, Ni²⁺ and Cu²⁺ ions in 4-chloro-2-nitrobenzoates experimentally determined at 76–303 K change from 3.89 to 4.82 μ_B for Co(II) complex, from 2.25 to 2.98 μ_B for Ni(II) 4-chloro-2-nitrobenzoate, and from 0.27 to 1.44 μ_B for Cu(II) complex. 4-chloro-2-nitrobenzoates of Co(II), and Ni(II) follow the Curie–Weiss law. Complex of Cu(II) forms dimer.     

Regio- and stereochemical aspects of bromochlorination of norbornene

Bromochlorination of norbornene whose chemo- and regio-selectivity is determined by the type of the halogenating reagent used was studied. Three isomeric bromochloronorbornanes (2-endo-bromo-3-exo-chloro-, 2-exo-bromo-3-endo-chloro-, and 2-exo-bromo-7-syn-chlorobicyclo[2.2.1.]heptanes), 2-exo-7-syn- and 2-exo-7-anti-dibromo- and-dichloronorbornanes, and 2-bromonortricyclane were isolated and characterized by¹H and¹³C NMR spectra. The spectral and structural characteristics of the resulting compounds are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2290–2295, November, 1998.     

4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III)

4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III) were obtained as mono-, di-, tri-or tetrahydrates with metal to ligand ratio of 1:3 and general formula Ln(C₈H₆ClO₃)₃·nH₂O, where n=1 for Ln=Er, n=2 for Ln=Tb, Dy, Tm, Y, n=3 for Ln=Ho and n=4 for Yb and Lu. The complexes were characterized by elemental analysis, FTIR spectra, TG, DTA and DSC curves, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate chelating ligand. All complexes are polycrystalline compounds. The values of enthalpy, ΔH, of the dehydration process for analysed complexes were also determined. The solubilities of heavy lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10⁻⁴ mol dm⁻³. The magnetic moments were determined over the range of 76–303 K. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.     

Sorption–Chromatographic Determination of Aniline, 4-Chloroaniline, and 2,5-Dichloroaniline in Air

Conditions were found for the chemisorption preconcentration of aniline, 4-chloroaniline, and 2,5-dichloroaniline from air using tubes packed with silica gel with immobilized 4-chloro-5,7-dinitrobenzofurazan and for the subsequent HPLC determination with diode-array detection. The maximum analyte recoveries (98, 90, and 75% for aniline, 4-chloroaniline, and 2,5-dichloroaniline, respectively) were achieved at a 2-cm thickness of the adsorbent layer (silica gel with a grain size of 0.1–0.3 mm impregnated with 3 wt % 4-chloro-5,7-dinitrobenzofurazan), an aspiration rate of 0.6–0.8 L/min, and an aspirated air volume of 10 L. Taking into account a tenfold preconcentration of analytes after the desorption, the detection limit for aniline is equal to 0.0007 mg/m³.     

127I MÖSSBAUER SPECTRA AND X-RAY CRYSTAL STRUCTURES FOR HYPERVALENT IODINE(III) COMPLEX OF HEXAFLUOROCUMYL ALCOHOL AND RELATED 10‐I‐3 COMPOUNDS

Abstract

The crystal structures of 1-chloro-3,3-bis(trifluoromethyl-1λ³,2(1H)-benzoiodoxole (I(hfpp)Cl) and 1-chloro-1λ³, 2-benzoiodoxole-3(1H)-one (I(ba)Cl) are determined. Although the T-shaped molecular structure for I(hfpp)Cl is quite similar to that for I(ba)Cl, the intermolecular interactions including the secondary bondings are significantly different; I(ba)Cl adopts an infinite chain structure with two longer I … O′ interactions, whereas I(hfpp)Cl has a dimeric structure with one I … O′ secondary bonding. The ¹²⁷I Mössbauer spectrum for I(hfpp)Cl is quite similar to those of hypervalent iodine(III) compounds having carboxylic and sulfonic ligands and chloride. This shows that the 5p electrons of the iodine(III) atom in I(hfpp)Cl are markedly withdrawn by apical oxygen and chlorine atoms almost equally, suggesting that the alcoholic oxygen atom of the ligand is quite electronegative.     

Synthesis of 2-chloro-5-hydroxynicotinonitrile: The required intermediate in the total synthesis of a hydroxylated metabolite of (S)-2-(3-t-butylamino-2-hydroxypropoxy)-3-cyanopyridine

A convenient method for the synthesis of 2-chloro-5-hydroxynicotinonitrile ( 10 ) via 5-amino-2-chloro-3-methylpyridine ( 3 ) is described. Subsequent conversions provided the basic metabolite 2 of (S)-2-(3-t-butylamino-2-hydroxypropoxy)-3-cyanopyridine ( 1 ). ¹³C Nmr data is also presented to characterize 2-chloro-5-fluoro-3-methylpyridine ( 5 ), a by-product in the Schiemann reaction having unexpected ¹H and ¹⁹F nmr spectra.     

Influence of the Mixed Adsorption Layer of 1‐Butanol/Toluidine Isomers on the Two Step Electroreduction of Zinc(II) Ions

Studies of mixed adsorption layers with respect to their influence on kinetics of Zn²⁺ ions reduction indicate dynamics of this process in the presence of inhibitor and accelerating substances. This effect can be seen as a much greater increase of standard constant rates compared with a similar increase without the inhibitor. 1‐Butanol was used as an inhibitor in the studies and p‐toluidine and m‐toluidine as accelerating substances. The adsorption measurements show that in the range of Zn²⁺ ion reduction potentials in the solutions containing 1‐butanol and the definite isomer of toluidine, toluidine plays a dominant role in establishing equilibrium in the mixed adsorption layer. The obtained values of the true standard constant rates of the transfer of the first electron k_s1^t and the second electron k_s2^t indicate that in each of the studied systems the stage of the first electron transfer is more strongly accelerated compared with the stage of the second electron transfer. The linear character of the dependence k_s1^t and k_s2^t in the function of the surface excess and in the function of 1‐butanol concentration indicates that active complexes are formed for each case of the mixed adsorption layer.     

Porous Proton- and Chloride-Ion Conducting Layers Based on Ethanolamine Derivatives of PVC on the Surfaces of Fabrics

Materials are produced with porous layers based on ethanolamine derivatives of PVC or compounds of active carbon with hydroxyethylcyclam derivatives of PVC with aqua complexes of chloride hydrogen cross-linked with the surface of cellulose or asbestos fabric. Their capacity for sorption with respect to hexane and benzene in the saturated vapor and liquid phases is determined. The dependences of current on voltage in a circuit are determined for bridges composed of these materials in air, and in the vapor and liquid phases of benzene and hexane between 3 M HCl solutions and 3 M HCl solutions containing 3 M CaCl₂. It is established that only H⁺ ions migrate along the bridges between the HCl solutions, and H⁺ and Cl^– ions were the only species that moved along the bridges between the HCl solutions containing CaCl₂. The voltages at which the movement of ions starts are determined, and constants characterizing the conductivity of the layers are found. It is shown that these parameters depend on the structure of a layer, the nature of the fabric, and the medium surrounding a bridge.

     

Isochinoline. 1. Mitteilung. Über die Umlagerung von α, α-Dialkylhomophtalimiden zu Derivaten des 1-Chlor-3, 4-dialkyl-isochinolins

On reinvestigation of the reaction of wet phosphorus oxychloride with α,α-dimethylhomophthalimide, 1-chloro-3-chloromethyl-4-methyl-isoquinoline and 1-chloro-4-chloromethyl-3-methyl-isoquinoline were isolated as the main products (aside from some substances resulting from a redox disproportionation). The production of these two substances can be rationalized by assuming a mechanism in which the rearrangement product is a protonated derivative of 3,4-dimethylene-3, 4-dihydroisoquinoline. With α, α-diethyl-homophthalimide the only isolated product was a derivative of 1-chloro-3, 4-diethyl-isoquinoline, with a chlorine atom in β-position of one of the ethyl groups, while with α-methyl-α-benzyl-homophthalimide the isolated product was 1,3-dichloro-4-methyl-isoquinoline, i.e. elimination had taken place instead of rearrangement. Also these results are in agreement with the proposed mechanism.     

Pyrolysis of 5-chloropentan-2-one and 4-chloro-1-phenylbutan-1-one. Participation of the carbonyl group

The rates of elimination of 5-chloropentan-2-one and 4-chloro-1-phenylbutan-1-one in the gas phase have been determined in a static system, seasoned with allyl bromide, and in the presence of the chain inhibitor propene. The reactions are unimolecular and follow a first-order rate law. The working temperature and pressure ranges were 339.4–401.1°C and 46–117 torr, respectively. The rate coefficients for the homogeneous reactions are given by the following Arrhenius equations: for 5-chloropentan-2-one, log k₁(s^?1) = (13.12 ± 0.88) - (207.8 ± 11.0)kJ/mol/2.303RT; and for 4-chloro-1-phenylbutan-1-one, log k₁(s^?1) = (12.28 ± 1.09) - (185.2 ± 12.0)kJ/mol/2.303RT. The carbonyl group at the γ position of the C? Cl bond of haloketones apparently participates in the rate of pyrolysis. The five-membered conformation appears to be a favorable structure for anchimeric assistance of the C?O group in the gas-phase elimination of chloroketones.     

C-Metallierte chirale Aloxide als d2- und d3-Reagenzien für die Synthese enantiomerenreiner Produkte (EPC-Synthese)

C-Metallated Chiral Alkoxides as d²–-and d³ -Regents for the Synthesis of Enantiomerically Pure Compounds (EPC-Synthesis) The chloroalcohols (S)-1 -chloro-2-propanol ( 1 ), (S)-1 -chloro-2-methyl-2-pentanol ( 4 ), (R)-3-chloro-2-methyl-1 -propanol ( 7 ), (R)-4-chloro-2-butanol ( 10 ), and (2R, 3R)- 4-chloro-3-methyl-2-butanol (14), really available from the esters of lactic, 3-hydroxy-2-methylpropanoic, and 3-hydroxybutanoic acid are subjected to sequential metallation first with BuLi (or MeMgCl) and then with lithium naphthalenide (or Li metal powder) to give solutions of the highly reactive C -metallated alkoxides 15, 22, 26, 27 , and 28 , respectively. - These chiral d²- and d³ -reagents may be added to aldehydes (non-diastereoselectively), ketones, and CO₂ to give 1, 3- or 1 4-dioles ( 18-21, 24, 29-33 ) or δ-lactones ( 35, 36 ). Thiolations with dibenzyl disulfide (→ 16, 34 ) and a deuteration (→ 17 , (S)-(1-²H)propan-2-ol) were also carried out. Independent synthesis of (S)-1-benzylthio-2-propanol ( 16 ) and comparison of the specific rotations establish that no loss enantiomeric purity occurs on the metallation route. The results described represent and extension of the applicability of simple chiral building blocks to EPC-synthesis.     

Spectrophotometric Determination of Dioxovanadium (V) Ion Using Some Halogen Derivatives of Phenylazo-Chromotropic Acid

A comparative study of the reaction of o-chloro-, m-chloro-, p-chloro-, p-bromo- and p-iodophenylazo-chromotropic acids with dioxovanadium (V) ion have shown that 1:1 and 1:2 violet water soluble complexes were formed at pH 4.5. The p-halogeno-derivatives were found to be very suitable reagents for spectrophotometric determination of VO⁺₂ up to 8 ppm. The application of these dyes as indicators in the spectrophotometric titration of VO⁺₂ with EDTA and the interference of a various cations and anions were reported.     

Concentrations of239,240Pu and238Pu in the surface air of Prague in 1993, 1994 and 1995

The activity concentration of^239,240Pu and²³⁸Pu in the surface air of Prague in the years 1993, 1994 and 1995 have been determined. The content of^239,240Pu in air in different monitoring periods of the years studied ranged from <0.5 to 5.5 nBq.m^–3. The source of^239,240Pu in air is the resuspension of fallout plutonium from the opsoil layer.     

The kinetics reaction of 1-chloro-2,3-epoxypropane with n-butyl and iso-butyl alcohols

The reactions of 1-chloro-2,3-epoxypropane with n-butyl and isobutyl alcohols and their 3-chloro-2-hydroxypropyl ethers, respectively, in the presence of boron fluoride diethyl etherate catalyst are of the first order with regard to 1-chloro-2,3-epoxypropane as well as to the catalyst. In the catalyst concentration range of 1.4 to 47.3 mmol/l., the participation of the catalyst in the reaction is incomplete. The mechanism of the reactions resembles S_N2 in regard to changes of activation entropy and influence of dielectric constant of the reaction medium upon the reaction rate. The established values of K (the ratio of propagation to initiation rates) are suitable for calculating the compositions of the adducts obtained. The experimentally obtained yields of 3-chloro-2-hydroxypropyl ethers of lower alcohols are compared with those calculated from the kinetically determined values of K.     

Magnetic, spectral, and thermal behaviour of 2-chloro-4-nitrobenzoates of Co(II), Ni(II), and Cu(II)

Some physicochemical properties of 2-chloro-4-nitrobenzoates of Co(II), Ni(II), and Cu(II) were studied. The complexes were obtained as mono-and dihydrates with a metal ion—ligand mole ratio of 1: 2. All complexes are polycrystalline compounds. Their colours depend on the kind of central ion: pink for Co(II) complex, green for Ni(II), and blue for Cu(II) complexes. Their thermal decomposition was studied only in the range of 293 K–523 K because it was found that on heating in air above 523 K 2-chloro-4-nitrobenzoates decompose explosively. Hydrated complexes lose crystallization water molecules in one step. During dehydration process no transformation of the nitro group to nitrito one took place. Their solubilities in water at 293 K are of the orders of 10⁻³-10⁻² mol dm⁻³. The magnetic moment values of 2-chloro-4-nitrobenzoates determined in the range of 76 K–303 K change from 3.48μ_B to 3.82μ_B for Co(II) complex, from 2.24μ_B to 2.83μ_B for Ni(II) 2-chloro-4-nitrobenzoate, and from 0.31μ_B to 1.41μ_B for Cu(II) complex. 2-Chloro-4-nitrobenzoates of Co(II) and Ni(II) follow the Curie—Weiss law, but the complex of Cu(II) forms dimer.