Analysis of tinuvin 1577 polymer additive in edible oils using on-line coupled HPLC-GC

An application of automated on-line HPLC-HRGC is described for direct analysis of edible oils for migrated polymer additives. The sample preparation, separating the additive from the oil triglycerides, is carried out using normal phase HPLC. The fraction of the eluent containing the additive is automatically transferred to a HRGC where a second and final separation of the additive from minor oil components takes place. The method compares well with off-line separation methods. Migration data for Tinuvin 1577 from PET and PC polymers as well as an unspecified experimental polymer is given. The advantages and disadvantages of using different edible oils as food simulants are discussed.     

Spectroscopic studies on inclusion properties of fullerenocalix[4]arene conjugates with metal ions

Metal-chelating properties-in the ground and excited states-of fullerenocalix[4]arenes containing two malonamide substituents at the upper rim and four alkyl ester chains at the lower rim have been studied by means of steady-state absorption, fluorescence spectroscopy, and time-resolved transient absorption spectra. In particular, the influence that Ag+ enforces on the fullerene electronic spectra is due to direct interactions between Ag+ and the surface of C60. The effects stemming from Na+, Mg2+, and Ba2+, on the other hand, are indirect and are introduced through chelating the metal ions to the calix[4]arene moiety. They strongly depend on the molecular structure of the fullerenocalix[4]arenes. No spectroscopic evidence was obtained for any influence caused by Mn2+, although the malonamide groups provide good chelating ability even for this transition metal ion.     

X-ray crystal structures of [XF(6)][Sb(2)F(11)] (X = Cl, Br, I); (35,37)Cl, (79,81)Br, and (127)I NMR studies and electronic structure calculations of the XF(6)(+) cations

The single-crystal X-ray structures of [XF(6)][Sb(2)F(11)] (X = Cl, Br, I) have been determined and represent the first detailed crystallographic study of salts containing the XF(6)(+) cations. The three salts are isomorphous and crystallize in the monoclinic space group P2(1)/n with Z = 4: [ClF(6)][Sb(2)F(11)], a = 11.824(2) A, b = 8.434(2) A, c = 12.088(2) A, beta = 97.783(6) degrees , V = 1194.3(4) A(3), R(1) = 0.0488 at -130 degrees C; [BrF(6)][Sb(2)F(11)], a = 11.931(2) A, b = 8.492(2) A, c = 12.103(2) A, beta = 97.558(4) degrees , V = 1215.5(4) A(3), R(1) = 0.0707 at -130 degrees C; [IF(6)][Sb(2)F(11)], a = 11.844(1) A, b = 8.617(1) A, c = 11.979(2) A, beta = 98.915(2) degrees , V = 1207.8(3) A(3), R(1) = 0.0219 at -173 degrees C. The crystal structure of [IF(6)][Sb(2)F(11)] was also determined at -100 degrees C and was found to crystallize in the monoclinic space group P2(1)/m with Z = 4, a = 11.885(1) A, b = 8.626(1) A, c = 12.000(1) A, beta = 98.44(1), V = 1216.9(2) A(3), R(1) = 0.0635. The XF(6)(+) cations have octahedral geometries with average Cl-F, Br-F, and I-F bond lengths of 1.550(4), 1.666(11) and 1.779(6) [-173 degrees C]/1.774(8) [-100 degrees C] A, respectively. The chemical shifts of the central quadrupolar nuclei, (35,37)Cl, (79,81)Br, and (127)I, were determined for [ClF(6)][AsF(6)] (814 ppm), [BrF(6)][AsF(6)] (2080 ppm), and [IF(6)][Sb(3)F(16)] (3381 ppm) in anhydrous HF solution at 27 degrees C, and spin-inversion-recovery experiments were used to determine the T(1)-relaxation times of (35)Cl (1.32(3) s), (37)Cl (2.58(6) s), (79)Br (24.6(4) ms), (81)Br (35.4(5) ms), and (127)I (6.53(1) ms). Trends among the central halogen chemical shifts and T(1)-relaxation times of XF(6)(+), XO(4)(-), and X(-) are discussed. The isotropic (1)J-coupling constants and reduced coupling constants for the XF(6)(+) cations and isoelectronic hexafluoro species of rows 3-6 are empirically assessed in terms of the relative contributions of the Fermi-contact, spin-dipolar, and spin-orbit mechanisms. Electronic structure calculations using Hartree-Fock, MP2, and local density functional methods were used to determine the energy-minimized gas-phase geometries, atomic charges, and Mayer bond orders of the XF(6)(+) cations. The calculated vibrational frequencies are in accord with the previously published assignments and experimental vibrational frequencies of the XF(6)(+) cations. Bonding trends within the XF(6)(+) cation series have been discussed in terms of natural bond orbital (NBO) analyses, the ligand close-packed (LCP) model, and the electron localization function (ELF).     

Kinetische und mechanistische untersuchungen von übergangsmetallkomplex-reaktionen : IX. Substitution von CO durch PPh3 in aminocarbinkomplexen: Präparative und kinetische untersuchungen

Pentacarbonyl(diethylaminocarbyne)chromium tetrafluoroborate, [(CO)₅₋ CrCNEt₂]BF₄ (I), reacts with PPh₃ with substitution of CO and formation of trans-tetracarbonyl(diethylaminocarbyne)triphenylphosphanechromium tetra-fluoroborate, trans-[PPh₃(CO)₄CrCNEt₂]BF₄ (III). Substitution of CO by PPh₃ in neutral trans-tetracarbonyl(halo)(diethylaminocarbyne)chromium complexes, trans-X(CO)₄CrCNEt₂ (IVa: X = Br, IVb: X = I), leads in a reversible reaction to the corresponding tricarbonyl complexes, mer-X(PPh₃)(CO)₃₋ CrNEt₂ (V), PPh₃ occupying the cis-position to the carbyne ligand. With PPh₃ in large excess both reactions follow a first-order rate law. This as well as the activation parameters (ΔH≠ = 104–113 kJ mol⁻¹, ΔS≠ = 64–71 J mol⁻¹ K⁻¹) indicate a dissociative mechanism.     

Ein- und zweikernige Dinitrosylkomplexe von Molybdän und Wolfram. Die Kristallstrukturen von (PPh3Me)2[WCl4(NO)2], (PPh3Me)2[MoCl3(NO)2]2 und von (PPh3Me)2[WCl3(NO)2]2

Mono- and Binuclear Dinitrosyl Complexes of Molybdenum and Tungsten. Crystal Structures of (PPh₃Me)₂[WCl₄(NO)₂], (PPh₃Me)₂[MoCl₃(NO)₂]₂, and (PPh₃Me)₂[WCl₃(NO)₂]₂ The complexes (PPh₃Me)₂[MCl₄(NO)₂] (M = Mo, W), and (PPh₃Me)₂[MCl₃(NO)₂]₂, respectively, are prepared by reactions of the polymeric compounds MCl₂(NO)₂ with triphenylmethylphosphonium chloride in CH₂Cl₂, forming green crystals. According to the IR spectra the nitrosyl groups are in cis-position in all cases. The tungsten compounds as well as (PPh₃Me)₂[MoCl₃(NO)₂]₂ were characterized by structure determinations with X-ray methods. (PPh₃Me)₂[WCl₄(NO)₂]: space group C2/c, Z = 4. a = 1874, b = 1046, c = 2263 pm, β = 119.99°. Structure determination with 3492 independent reflexions, R = 0.057. The compound consists of PPh₃Me^⊕ ions, and anions [WCl₄(NO)₂]^2? with the nitrosyl groups in cis-position (symmetry C_2v). (PPh₃Me)₂[WCl₃(NO)₂]₂: Space group C2/c, Z = 4. Structure determination with 2947 independent reflexions, R = 0.059. (PPH₃Me)₂[MoCl₃(NO)₂]₂: Space group P1 , Z = 1. a = 989, b = 1134, c = 1186 pm; α = 63.25°, β = 80.69°, γ = 69.94°. Structure determination with 3326 independent reflexions, R = 0.046. The compounds consist of PPh₃Me^⊕ ions, and centrosymmetric anions [MCl₃(NO)₂]₂^2?, in which the metal atoms are associated via MCl₂M bridges of slightly different lengths. One of the NO groups is in an axial position, the other one in equatorial position (symmetry C_2h).     

Dioxomolybdenum(VI) complexes containing 1-alkyl-2-ethyl-3-hydroxy-4-pyridin-4(1H)-ones

Dioxomolybdenum(VI) complexes derived from ethyl maltol (2-ethyl-3-hydroxy-4-pyrone) and 1-alkyl-2-ethyl-3-hydroxy-4-pyridin-4(1H)-ones have been prepared and characterized using physical methods including ¹H- and ¹³C-n.m.r. spectroscopy, i.r., elemental analysis, and X-ray diffraction for the pyrone and 3-methylpyridine pyridinone derivatives. The octahedral complexes have the general formula cis-MoO₂L₂ where L = the deprotonated pyrone or pyridinone ligand.     

Deprotonated and non-deprotonated cobalt(II) complexes of the bis-amide tetradentate ligand N,N′-(dipicolyl)-1,8-naphthylene diamine. Three different modes of coordination by the ligand

The preparation and some properties of the cobalt(II) complexes Co(LH₂)Cl₂·2H₂O, Co(LH₂(NCS)₂ and CoL·H₂O (whereLH₂=N,N-(dipicolyl)-1,8-naphthylenediamine) are reported. On the basis of magnetic moments, visible reflectance and IR data, the structure is proposed to be pseudo-octahedral for Co(LH₂)Cl₂·2 H₂O, pseudo-tetrahedral for Co(LH₂)(NCS)₂ and square planar for CoL·H₂O.

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Deprotonierte und Nicht-deprotonierte Co(II)-Komplexe des vierzähnigen Bisamid-Liganden N,N-(Dipicolyl)-1,8-naphthyldiamin. Drei verschiedene Koordinationstypen

Zusammenfassung Es werden die Darstellung und einige Eigenschaften der Kobalt(II)-Komplexe Co(LH₂)Cl₂·2 H₂O, Co(LH₂)(NCS)₂ und CoL·H₂O [LH₂=N,N-(dipicolyl)-1,8-naphthylendiamin] diskutiert. Auf der Grundlage von magnetischen Momenten, von Daten der sichtbaren Reflektions-und IR-Spektren wird eine pseudooctaedrische Struktur für Co(LH₂)Cl₂·2H₂O, eine pseudotetraedrische für Co(LH₂)(NCS)₂ und eine planar-quadratische für CoL·H₂O vorgeschlagen.

     

Synthesis of carbaalane halogen derivatives

The carbaalane halogen derivatives [(AlX)(6)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(3))(6)] (X = F (9), Cl (7), Br (10), I (11)) were prepared in toluene from [(AlH)(6)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(3))(6)] (6) and BF(3).OEt(2), BX(3) (X = Br, I), Me(3)SnF, and Me(3)SiX (X = Cl, Br, I), respectively. A partially halogenated product [(AlH)(2)(AlX)(4)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(3))(6)] (12) (X = Cl (approximately 40%), Br (approximately 60%)) was obtained from 5 and impure BBr(3). [(AlH)(6)(AlNMe(3))(2)(CCH(2)Ph)(6)] (5) was converted to [(AlX)(6)(AlNMe(3))(2)(CCH(2)Ph)(6)] (X = F (13), Cl (14), Br (15), I (16)) using BF(3).OEt(2) and Me(3)SiX (X = Cl, Br, I), respectively. The X-ray single-crystal structures of 11.C(6)H(6), 12.3C(7)H(8), 13.6C(7)H(8), and 15.4C(7)H(8) were determined. Compounds 7 and 9-11 are soluble in benzene/toluene and could be well characterized by NMR spectroscopy and MS (EI) spectrometry. The results demonstrate the facile substitution of the hydridic hydrogen atoms in 5 and 6 by the halides with different reagents.     

Some new aspects of a HPLC-method for the determination of traces of formaldehyde in air

Summary A practicable method was developed for the routine determination of formaldehyde in air. Formaldehyde is sampled in small sampling tubes filled with Chromosorb P, coated with 2,4-dinitrophenylhydrazine (= DNPH). The sorbent is extracted with acetonitrile, and the different DNPhydrazones were separated by reversed-phase HPLC. UV-detection at = 345 nm was compared with electrochemical detection. The detection limit was 100 pg for UV- and 50 pg for electrochemical detection with a linear range of more than 3 decades, respectively. For the determination of formaldehyde in air the detection limit is 10 ppb with an average recovery of 99.3% and an estimated relative standard deviation S of 1.5%. This method was compared with the sampling by impingers using the same separation and detection method.

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Einige neue Aspekte einer HPLC-Methode zur Spurenbestimmung von Formaldehyd in Luft

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday