Characterization of degradation products of poly[(3,3,3-trifluoropropyl)methylsiloxane] by nuclear magnetic resonance spectroscopy, mass spectrometry and gas chromatography

Poly[(3,3,3-trifluoropropyl)methylsiloxane] (PTFPMS) was treated with the solvents acetone, ethyl acetate and methanol and its degradation products were analyzed with multiple techniques. ¹H, ²⁹Si and ¹⁹F nuclear magnetic resonance (NMR) spectroscopy were useful for the characterization of the intact polymers and for the determination of cyclosiloxanes. Cyclosiloxanes with a ring size of up to 23 were quantified by gas chromatography. The only degradation products found were TFPmethyl-cyclosiloxanes. 1,3,5,7-Tetrakis(TFPmethyl)-cyclotetrasiloxane was predominant, and (TFPmethyl)cyclotri-, penta- and hexasiloxane could be detected at lower concentrations. The identity of cyclic degradation products with a ring size of up to 6 was unambiguously confirmed by direct infusion mass spectrometry. The TFPmethyl-cyclosiloxanes were successfully ionized by electrospray ionization in the negative mode. None of the techniques applied gave hints to other degradation products such as short linear oligomers. Almost complete degradation of PTFPMS occurred in acetone and methanol, while degradation is distinctly reduced in ethyl acetate.     

Characterization of stationary phases for gas chromatography by 29Si nuclear magnetic resonance spectroscopy III. Carborane-siloxane copolymers

Five bis(dimethylsilyl)-m-carborane-siloxane polymers with methyl, phenyl, and 2-cyanoethyl ligands were characterized by (1)H, (11)B, (13)C, and (29)Si nuclear magnetic resonance (NMR) spectroscopy. All relevant chemical shifts are reported, whereas signal assignment was confirmed by 2D NMR spectroscopy. The chemical composition of the polymers was calculated from the (1)H and (29)Si NMR spectra. Only (29)Si NMR spectroscopy was able to quantify the methoxy end group, from which the average molecular weights were calculated. The copolymer Dexsil 300 turned out to have a regular microstructure, whilst the terpolymers Dexsil 400 and Dexsil 410 have only partly regular sequences. (11)B NMR spectroscopy confirmed the m-carborane structure and revealed some low molecular weight impurities.     

Eine neue Azepinring-Synthese

A New Azepine-Ring Synthesis A new one-step synthesis of an azepine ring is described. The 2H-pyran-2-one ring of methyl cumalate ( 8 ) or cumalaldehyde ( 2 ) upon reaction with an 1-aminoacryl derivative, e.g. 1 or 6 , is opened with subsequent decarboxylation to give a 1-aminobutadiene derivative that undergoes an electrocyclic ring closure to the azepine ring (Schemes 1 and 2).     

C45- und C50-Carotinoide. 4. Mitteilung. Synthese von optisch aktiven cyclischen C20-Bausteinen und von (2R,2′R)-2,2′-Bis(4-hydroxy-3-methyl-2-butenyl)-β,β-carotin ( = C.p. 450)

C₄₅- and C₅₀-Carotenoids: Synthesis of Optically Active Cyclic C₂₀-Building Blocks and of (2R,2′R)-2,2′-Bis(4-hydroxy-3-methyl-2-butenyl)-β,β-carotene ( = C.p. 450) The synthesis of the optically active C₂₀-building blocks (R)- 26 and (R)- 39 and of the optically active cyclic C₅₀-carotenoid C.p. 450 ( 3 ) starting from (?)-β-pinene is reported.     

One- electron transfer properties and herbicidal activity of diquaternary salts of 2,4-di-(4-pyridyl)-1,3,5-triazines

Diquaternary salts of 2,4-di-(4-pyridyl)-1,3,5-triazines have been prepared. The salts can be regarded as reversible one electron transfer systems with redox potentials (E₀) of about ?0·44 V in the pH range 7·0–8·5. 2,4-Bis-(4-methyl-4-pyridinio)-1,3,5-triazinediium dihalides are effective post-emergent herbicides at application rates of 4–6 kg/hectare.     

Competing interactions in the tetranuclear spin cluster [Ni[(OH)(2)Cr(bispictn)](3)]I(5).5H(2)O. An inelastic neutron scattering and magnetic study

The properties of the spin state manifold of the tetranuclear cluster Ni[(OH)(2)Cr(bispictn)](3)]I(5).5H(2)O (bispictn = N,N'-bis(2-pyridylmethyl)-1,3-propanediamine) are investigated by combining magnetic susceptibility and magnetization measurements with an inelastic neutron scattering (INS) study on an undeuterated sample of Ni[(OH)(2)Cr(bispictn)](3)]I(5).5H(2)O. The temperature dependence of the magnetic susceptibility indicates an S = (1)/(2) ground state, which requires antiferromagnetic interactions both between Cr(3+) and Ni(2+) ions and among the Cr(3+) ions. INS reveals potential single-ion anisotropies to be negligibly small and enables an accurate determination of the exchange parameters. The best fit to the experimental energy level diagram is obtained by an isotropic spin Hamiltonian H = J(CrNi)(S(1)().S(4)() + S(2)().S(4)() + S(3)().S(4)()) + J(CrCr)(S(1)().S(2)() + S(1)().S(3)() + S(2)().S(3)()) with J(CrNi) = 1.47 cm(-)(1) and J(CrCr) = 1.25 cm(-)(1). With this model, the experimental intensities of the observed INS transitions as well as the temperature dependence of the magnetic data are reproduced. The resulting overall antiferromagnetic exchange is rationalized in terms of orbital exchange pathways and compared to the situation in oxalato-bridged clusters.     

Reaktionen des Cumalinsäure-methylesters und Cumalinaldehyds mit ambidenten Nucleophilen

Reactions of Methyl Coumalate and Coumalaldehyde with Ambident Nucleophiles Methyl coumalate and coumalaldehyde show great diversity in their reactions with ambident nucleophiles both depending upon the 2H-pyran-2-one derivative and the nature of the ambident nucleophile used. The products are either pyridine or pyrimidine derivatives.     

Citrus-Carotinoide. 1. Mitteilung. Synthese von Apocarotinoiden mit einer anders gelagerten Methylgruppe; Strukturaufklärung von Citrus-Carotinoiden

Synthesis of Apocarotenoides with a Shifted Methyl Group; Structure Elucidation of Citrus-Carotenoides With regard to the investigation of the biosynthesis of the C₃₀-carotenoids in citrus fruits apocarotenoids with a methyl group shifted by one position (diapocarotenoids) were synthesized. Characteristical differences, especially in the 270-MHz-¹H-NMR. spectra between the apo- and the diapocarotenoids are reported. The comparison of the natural pigments with the synthetic compounds proves that the natural products belong to the apocarotenoids as has been postulated earlier.