Solid-Phase Extraction/High-Performance Liquid Chromatography-Electrospray Mass Spectrometry to Determine Endocrine Disruptors in Water Samples

A method for determining a group of endocrine-disrupting compounds in water samples was developed. This method was based on high-performance liquid chromatography-(electrospray) mass spectrometry (HPLC-(ESI)MS), working in negative ionization (NI) mode. Solid-phase extraction (SPE) with 200 mg Lichrolut EN was used to preconcentrate the water samples. The performance of the method was tested with several environmental water samples such as river, marine and influent and effluent water from a sewage treatment plant (STP). The limits of detection (LODs) of the method were between 0.001 and 0.3 g L^–1 under selective-ion monitoring (SIM) acquisition mode for 500 mL of river, marine and STP effluent water samples and between 0.01 and 3 g L^–1 for 100 mL of STP influent water. We determined some endocrine disruptors, such as diuron, bisphenol A (BPA), estrone, 4-tert-butylphenol (4-t-BP), 4-tert-octylphenol (4-t-OP) and pentachlorophenol (PCP), in several water samples at levels of g L^–1.     

Thermochemical Studies for Determination of the Standard Molar Enthalpies of Formation of Alkyl-Substituted Furans and Some Ethers

The standard molar enthalpies of vaporization _l ^g H _m ^º of 2,5-dimethylfuran, 2-tert-butylfuran, 2,5-di-tert-butylfuran, cyclopentenyl methyl ether, cyclohexenyl methyl ether, and tert-amyl methyl ether were obtained from the temperature variation of the vapor pressure measured in a flow system. The standard (p° = 0.1 MPa) molar enthalpies of formation _f H _m ^º (1) at the temperature T = 298.15 K were measured using combustion calorimetry for 2,5-dimethylfuran, 2-tert-butylfuran, and 2,5-di-tert-butylfuran. From the derived standard molar enthalpies of formation for gaseous compounds, ring correction terms and non-nearest neighbor interactions useful in the application of the Benson group additivity scheme were calculated.     

p-tert-Butylcalix[5]arene: a New Synthetic Pathway and Crystal Structure of the N,N-Dimethylformamide Complex

The formation of p-tert-butylcalix[5]arene by the opening ofp-tert-butyldihomooxacalix [4]arene and the addition of a monomer has beenstudied. Various facets, including the effects of bases and the nature ofthe monomer added to the p-tert-butyldihomooxacalix[4]arene, have beeninvestigated. p-tert-Butylcalix[5]arene can be prepared in yields up to30%. The structure of its 1 : 2 complex with DMF has been determinedby X-ray crystallography. Crystals are triclinic, space group P¯1, a =1428.2(3) pm, b = 1837.3(3) pm, c = 1276.1(2) pm, = 108.98(1)°, = 105.02(2)°, = 95.21(1)°, Z = 2, D _c = 1.059 kg m^-3,final R value = 0.087. The macrocycle adopts a cone conformation, one guestenclosed inside the cavity, the other one outside.     

Determination of Natural and Synthetic Endocrine-Disrupting Chemicals (EDCs) in Sewage Based on SPE and MEKC with Amperometric Detection

An integrated analytical method to monitor five environmental endocrine disrupting chemicals (EDCs): 2,4-dichlorophenol (DCP), 4-tert-butylphenol (BP), bisphenol A (BPA), 17α-ethynylestradiol (EE2) and 4-n-nonylphenol (NP), was developed for the first time, based on a solid-phase extraction and miniaturized micellar electrokinetic chromatography with amperometric detection. In order to get the optimum conditions of their separation and detection, several parameters including pH and concentration of running buffer, concentration of micelle, separation voltage and injection time were studied and optimized. The five EDCs were well separated under the optimum conditions within 12 min. This method was successfully applied for the determination of these five EDCs in sewage influent sample. Satisfactory extraction performances from sewage sample was obtained by solid-phase extraction, using a C₁₈ cartridge. Quantitative analysis showed that DCP, BP, and BPA existed at μg L^?1 level in the selected sample, while EE2 and NP were not detected.     

Oxygenation of 4-tert-butylcatechol catalysed by a manganese(II) complex: implications for extradiol catechol dioxygenases

An N donor tetradentate manganese complex, [Mn^II(bispicen)Cl₂] (A) [bispicen = N,N-bis(2-pyridylmethyl)-1,2-ethanediamine)] catalyses the oxidative cleavage of 4-tert-butylcatechol (1) in the presence of O₂. The oxygenated products were isolated by t.l.c. and column chromatography and characterised by ¹H-, ¹³C-n.m.r., DEPT, i.r. and u.v.–vis. spectroscopy. The oxygenated products as well as other spectral evidence suggest that the oxygenation occurs via a 4-tert-butylsemiquinone bound complex, [Mn^II(bispicen)(4-sq)]⁺ (4-sq = 4-tert-butylsemiquinone). ¹H-n.m.r. spectroscopy suggests that the oxygenation follows multiple pathways. Isolation of the products suggests that the oxygenations proceed in an extradiol fashion and a probable mechanism is suggested. Some intradiol cleaved products have also been detected. E.s.r. spectroscopy suggests that manganese(II) is ultimately converted into the manganese(IV) species.     

Monoetherification of tert-Butylated Pyrocatechols upon Irradiation of Their Solutions in Hydrocarbons

Products of reactions of tert-butylated pyrocatechols with alkyl radicals were studied. The major products formed upon -irradiation of deaerated solutions of 4-tert-butyl- and 3,5-di-tert-butylpyrocatechol in hexane and cyclohexane are monoalkyl ethers, which were identified by NMR spectroscopy (¹H, ¹³C, ¹H-¹H NOESY technique) and gas chromatography-mass spectrometry.     

Pyrazolyl-pyrimidine based ligands in palladium catalyzed copolymerization and terpolymerization of CO/olefins

Cationic palladium(II) complexes of the type containing bisnitrogen ligands with a pyrazole moiety were synthesized from the corresponding neutral derivatives [PdClMe(N-N′)]. Their characterization by ¹H and ¹³C NMR spectroscopy in solution evidences the presence of the Pd-Me group cis to the pyrazole ring. The catalytic behaviour of the cationic complexes in CO/4-tert-butylstyrene copolymerization and CO/ethylene/4-tert-butylstyrene terpolymerization was investigated. Productivity was greatly enhanced when the reaction was carried out in 2,2,2-trifluoroethanol (TFE). Molecular weights and polydispersity (M_w/M_n) of the obtained polyketones resulted among the best reported for C_s-bisnitrogen planar ligands.     

Intermediates of Asymmetric Oxidation Processes Catalyzed by Vanadium(V) Complexes

The [VO(acac)₂]/Schiff base [R-2-(N-3,5-di-tert-butylsalicylidene)amino-2-phenyl-1-ethanol, S-2-(N-3,5-di-tert-butylsalicylidene)amino-3,3-dimethyl-1-butanol, S-2-(N-3,5-di-tert-butylsalicylidene)amino-3-methyl-1-butanol, or R-2-(N-3,5-di-tert-butylsalicylidene)amino-3-phenyl-1-propanol]/H₂O₂ catalytic systems for the asymmetric oxidation of sulfides and the [VO(acac)₂]/(3bR,4aR)-2-(3,4,4-trimethyl-3b,4,4a,5-tetrahydrocyclopropa[3,4]cyclopenta[1,2-c]pyrazol-1-yl)ethanol/tert-butyl hydroperoxide/TBHP and VO(OAlkyl)₃/[2,2]paracyclophane-4-carboxylic acid N-(1,1-dimethylethyl)-N-hydroxamide/TBHP catalytic systems for the asymmetric epoxidation of allylic alcohols were studied using ¹³C, ⁵¹V, and ¹⁷O NMR spectroscopy. The key intermediates of these systems (peroxo and alkylperoxo complexes of vanadium(V)) were detected, their structures in solution were studied, and the reactivity was evaluated.     

Products and kinetics of the thermal decomposition of (l-(−)-menthyl)[2,2′-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphite ozonide

Two conformers (chair, boat) of [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphite ozonide have been obtained by the low temperature ozonization (–80 °C) of [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphite. It was determined that decomposition of the ozonide is first order with the rate constant logk ₀ = (10.92±1.10)–(14.02±1.25)/gq ( = 2.303RT, kcal mol^–1), leading to [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphate and oxygen (including singlet oxygen). Conformational transitions (chair-boat) for [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphate have been registered by³¹P NMR spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1758–1761, October, 1994.This work was supported by Russian Foundation for Basic Research (Project No. 93-03-532l).     

Anion and Cavity Effects on the Complexation Behavior of Di-Aza-Benzo-Crown-Ether Calix[4]arene towards Zn(II) Ions

A novel compound, 25, 27 - N,N - di - ((2 -ethoxy)benzyl)butylenediamine - p - tert- butylcalix[4]arene, 1, has beensynthesized by reducing its Schiff base derivative. Inclusion studies by¹H-NMR spectroscopy in a mixed solvent (CD₃OD/CDCl₃) of25,27-N,N-di-((2-ethoxy)benzyl)propylenediamine-p-tert-butylcalix[4]arene,2, and 1 with Zn(II) ions, where counter anions are Cl^-, Br^-, I^- and NO ₃ ^- ,show that both ligands can bind Zn(II) to a different extent depending onthe counter anions and the cavity size of the ligands. The stabilityconstants of ZnX₂–1 (ZnX₂-2) complexes where X = Cl^-, Br^-, I^- and NO ₃ ^- are 1.4 ± 0.1 (1.6 ± 0.1), 1.7 ± 0.1 (1.9 ±0.1), 2.2 ± 0.1 (2.7 ± 0.1) and 4.7 ± 0.1 (6.0 ±0.1), respectively. The calix[4]arene unit of the ligand 2 was found to havea structural change from cone to partial cone conformation upon binding toZnCl₂, ZnBr₂ and ZnI₂.     

Complexation of Porphyrin-Appended Guests by Calix[4]arene-Appended Cyclodextrins

A calix[4]arene based -cyclodextrin dimerand tetramer (1 and2, Figure 1) were synthesized by covalentattachment of amono(2-O-xylylamino)--cyclodextrinderivative to calix[4]areneplatforms, bi- or tetrafunctionalized withcarboxylic acid groups at their upperrims. The complexation of porphyrin-basedguest molecules by these hosts inwater was studied using microcalorimetry.Tetrakis(4-phenylsulfonato)porphyrin(TsPP) binds to 2 in a 1 : 2 (host : guest)fashion with enhanced bindingstrength (K₁ = 6.6 × 10⁶ M ^-1) ascompared to the monomeric TsPP–CDinteraction (K = 8.8 × 10⁵ M ^-1). Thisenhancement is attributed tothe involvement of two cyclodextrin units in theaccommodation of one TsPP guest.Increase of the number of 4-sulfonatophenyl siteson the guest by generating the-oxo-dimer of the iron(III) complex of TsPPled to further increase of thebinding strength owing to participation of three-cyclodextrin cavities of2 (K = 1.5 × 10⁷ M ^-1). The geometricincompatibility betweenhost and guest, stemming from the fact that both TsPPand its -oxo-dimer arefairly small compared to the multi-cyclodextrin hosts,probably explains why theenhancement is still moderate. A much more pronouncedincrease in complexationstrength was achieved with p- and m-pyridylporphyrinextended withp-tert-butylbenzyl guest sites. Theseguests are large enough to accommodatethree to four -cyclodextrin units. The bettermatch in size between host and guestgave association constants up 10⁸ and 10⁹ M ^-1for the -cyclodextrindimer and tetramer, respectively. In fact, the 1 : 1complex betweentetrakis(p-tert-butylbenzyl)-p-pyridylporphyrinand 2(K = 5 × 10⁹ M ^-1) is the strongestreported for cyclodextrin–porphyrininteractions.     

Reaction Between 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione and <Emphasis Type="Italic">tert</Emphasis>-Butyl Isocyanide in the Presence of Primary or Secondary Amines

Summary. 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione (the condensation product of Meldrums acid and acetone) reacts smoothly with tert-butyl isocyanide in the presence of primary or secondary amines to produce N-tert-butyl-2,2-dimethylbutyramide derivatives and/or 1-tert-butyl-4,4-dimethyl-2,5-dioxopyrrolidine-3-carboxamides in good yields.     

Synthesis of 2-Tert-butylimino-3-hepta-O-benzoyl-β-D-lactosylimino-4-S-benzyl-6-arylimino-2,3-dihydro-1,3,5-thiadiazines

A new series of synthesis of 2-tert-butylimino-3-hepta-O-benzoyl-β-D-lactosylimino-4-S-benzyl-6-arylimino-2,3-dihydro-1,3,5-thiadiazines (hydrochloride) were synthesized by the interaction of 1-aryl-5-hepta-O-benzoyl-β-D-lactosyl-2-S-benzyl-2,4-isodithiobiurets with tert-butyl isocyanodichloride. The identities of these newly synthesized N-lactosides have been established on the basis of usual chemical transformations and infrared, ¹H NMR, and mass spectral analysis.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Amino acid analysis by using comprehensive two-dimensional gas chromatography

The separation characteristics of alkylchloroformate-derivatised amino acids (AAs) by using comprehensive two-dimensional gas chromatography (GC×GC) is reported. The use of a low-polarity/polar column set did not provide as good a separation performance as that achieved with a polar/non-polar column set, where the latter appeared to provide less correlation over the separation space. The degree of component correlation in each column set was estimated by using the correlation coefficient (r²; for ¹t_R and ²t_R data) with the low-polarity/polar and polar/low-polarity sets returning correlation coefficients of 0.86, and 0.00 respectively, under the respective conditions employed for the experiments. The 1.5-m non-polar ²D column (0.1-mm ID; 0.1-m film thickness) gave peak halfwidths of the order of 50–80 ms. Linearity of detection was good, over a three order of magnitude concentration range, with typical lower detection limit of ca. 0.01 mg L^–1, compared with 0.5 mg L^–1 for normal GC operation with splitless injection. The method was demonstrated for analysis of AAs in a range of food and beverage products, including wine, beer and honey. The major AA in these samples was proline. The Heineken beer sample had a relatively more complex and more abundant AA content compared with the other beer sample. The wine and honey samples also gave a range of AA compounds. Repetition of the sample preparation/analysis procedure for the honey sample gave acceptable reproducibility for individual AAs.     

Alkyl (C<Subscript>10</Subscript>, C<Subscript>12</Subscript>, C<Subscript>14</Subscript> and C<Subscript>16</Subscript>) triphenyl phosphonium bromide influenced cloud points of nonionic surfactants (Triton X 100, Brij 56 and Brij 97) and the polymer (Polyvinyl methyl ether)

The clouding points (CP) of the nonionic surfactants p-tert-octyl phenyl polyoxyethylene ether (Triton X 100), Brij-56 and Brij-97, and the water soluble polymer polyvinylmethylether (PVME) have been measured in the presence of the ionic surfactants alkyl (C₁₀, C₁₂, C₁₄ and C₁₆) triphenyl phosphonium bromides (ATPBs). The threshold additive concentrations required for efficient CP enhancement of the systems that were studied have been determined. Considering CP as the threshold state of phase separation, the energetics of the process at different additive concentrations has been evaluated. The spontaneity of free energy of the clouding process (G _c ⁰ ) at the transition concentrations followed the order PVME > TX 100  Bj 56 > Bj 97. The clouding process has been found to be energetically endothermic with fairly large enthalpy and entropy changes that nicely compensate each other. The compensation temperature has been evaluated and compared with different types of the clouding agents.This revised version was published online in January 2005 with corrections to the names of the authors.     

Inclusion extraction of alkali metals by emulsion liquid membranes bearing nano-baskets

Nano-assisted inclusion separation of alkali metals from basic solutions was reported by inclusion-facilitated emulsion liquid membrane process. The novelty and significance of this study is application of nano-baskets of calixarene in the selective and efficient separation of alkali metals, as both carrier and surfactant. For this aim, four derivatives of p-tert-calix[4]arene bearing different sulfonamide moieties were synthesized and their inclusion-extraction parameters were optimized. Maximum extraction was achieved using calixarene scaffold 03 (3.45 × 10^?2 M) as carrier/demulsifier, commercial kerosene as diluent in membrane, sulphonic acid (0.2 M) and ammonium carbonate (0.4 M) as the strip and the feed phases, the phase and the treat ratios of 0.8 and 0.3, mixing speed (300 rpm), and initial solute concentration (100 mg/L). The selectivity of membrane over more than ten interfering cations was examined and the results reveled that under the optimized operating conditions, the extraction percent of alkali metals was 98–99 %.     

Hypervalent and binuclear silicon and germanium derivatives from bis-(3,5-di-tert-butyl-2-phenol)-oxamide

The reactions of bis-(3,5-di-tert-butyl-2-phenol)oxamide (1) with Cl₂SiR₂ (Me or Ph) or Cl₂GeR₂ (Me, nBu or Ph) in THF provided binuclear pentacoordinated silicon and germanium compounds: bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylsilane (2), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenylsilane (3), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylgermane (4), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-di-n-butylgermane (5) and bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenylgermane (6). The mono-nuclear tetracoordinated silicon compounds N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(dimethylsilane) (8) and N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(diphenylsilane) (9) were synthesized from N-(3,5-di-tert-butyl-2-phenol)acetamide (7) and Cl₂SiR₂ (R = Me and Ph). Comparison of the ²⁹Si NMR chemical shifts of the penta- (2 and 3) and tetracoordinated (8 and 9) silicon compounds provided information about the intramolecular coordination of the carbonyl group to the silicon atom. Compounds 3 and 6 were characterized by single-crystal X-ray analyses. They have planar hexacyclic structures where the central atoms present distorted tbp geometries with one nitrogen and two carbon atoms in equatorial positions and two oxygen atoms in apical positions.     

The Synthesis and Structure of Selected Methyl (3,4-Di-O-acetyl-2-deoxy-2-hydroxyimino-d-arabino-hexopyranosid)urontes

Abstract

Dimeric methyl (3,4-di-O-acetyl-2-deoxy-2-nitroso-α-d-glucopyranosyl chloride)uronate (1) reacts with nucleophiles such as: ethanol, pyrazole, methyl N-tert-butyloxycarbonyl-L-serinate to give corresponding glycosides. The stereospecifity of the glycosidation reaction depends mainly on the employed nucleophile. The configuration and conformation of the obtained glycosides were established on the basis of ¹H NMR and polarimetric data, and additionally the structure of 1-(methyl 3,4-di-O-acetyl-2-deoxy-2-(Z)-hydroxyimino-α-d-arabino-hexopyranosyluronate)pyrazole (6), was supported by X-ray diffraction data.