Search results for "CLEAVAGE"
showing 10 items of 281 documents
Über den thermischen abbau des poly(ɛ-caprolacton)s
1977
The thermal and electron impact induced degradation reactions of poly(e-caprolactone) {poly[oxy(1-oxohexamethylene)]} were investigated in a mass spectrometer. It can be shown that the favorated thermal degradation reaction is the cleavage of the ester bond and formation of ω-hydroxyl and ketene endgroups (Eq. (iii)) and with a lower intensity the cleavage of the OCH2-bond and formation of carboxyl-and pentenyl endgroups (Eq. (vii)). After electron impact and fragmentation of the pyrolysis products to carboxonium ions an elimination of caprolactone via a “zip”-mechanism can be observed (Eq. (v)).
PHOSPHORORGANISCHE VERBINDUNGEN 105.1Synthese chiraler und achiraler ditertiärer 1-Phosphino-2-Aminoethan-Derivate ([dbnd]P [sbnd]CH2[sbnd]CHR[sbnd]N…
1983
Abstract Primary amines with an optical active ligand add to vinyl- and propenylphosphonium salts according the reaction schemes (5) and (6), forming compounds of the type E and F. F contains a new asymmetric center in the bridge giving rise to the formation of a mixture of diastereomers, which can be resolved. Phosphonium salts of type E and F with a benzyl group on the phosphonium center are cleaved reductively by alkali amalgams (Li/Hg; Na/Hg; K/Hg) forming tertiary phosphines with an aminogroup in the β-position. The reductive cleavage with alkali amalgams is superior to the cathodic cleavage. Application: The synthesis of Ni(O)- and Pd(O)-complexes of type J fails. Bis-phosphine comple…
Untersuchungen zum oxidativen abbau nativer cellulose. I. Das anfangsstadium des heterogenen abbaus von alkalicellulose aus baumwolle und eine bezieh…
1973
Behandlung nativer Baumwollcellulose mit NaOH verschiedener Konzentration uber langere Zeiten unter Reinstickstoff vermindert den STAUDINGER-Index der Cellulose in CUOXAM und des daraus hergestellten Cellulosetrinitrats (CTN) in Aceton um einen erheblichen Betrag. Lichtstreuungsmessungen zeigen, das wahrend dieses Prozesses das Molekulargewicht erhalten bleibt, wahrend der Tragheitsradius abnimmt und der 2. Virialkoeffizient zunimmt. Die enge Molekulargewichtsverteilung des nativen Produkts bleibt hierbei erhalten. Schwache Sauerstoffzufuhr erhoht zunachst die Viskositat, um sie erst bei langerem Abbau zu erniedrigen. Diese Phanomene werden folgendermasen gedeutet : Die Cellulosemolekule li…
Ultrasound assisted reductive cleavage of sesquiterpene γ-enonelactones
1995
Abstract Ultrasound enhances the rate of reductive cleavage of the C 6 -oxygen bond of several cis - and trans - sesquiterpene γ-enonelactones. Interestingly ultrasound overrides the stereoelectronic requirements for the reductive cleavage of the most usually occurring sesquiterpene trans -lactones.
ChemInform Abstract: Synthesis of the First Benzodiselenagermoles and One Spirobisdiselenagermole.
2010
Abstract The first examples of compounds R1R2GeSe2C6H4R3 (R1,R2=CH3 C2H5, C3H2, n-C4H9, i-C5H11, Ph, p-CH3Ph. R3=H, CH3, OCH3) were easily obtained (40–80% yield) from electrophilic cleavage of diselenophenylene zirconocenes by dialkyl or diaryl dichlorogermanes. The synthesis of a spirodi-selenagermole was achieved in the same way using germanium tetrachloride. Analytical data, 1H and 77Se NMR. mass spectra are perfectly consistent with the expected structures.
Gallium(III) and Indium(III) Complexes with meso-Monophosphorylated Porphyrins: Synthesis and Structure. A First Example of Dimers Formed by the Self…
2017
International audience; The synthesis and structural characterization, both in solution by means of H-1 and P-31 NMR and UV-vis spectroscopies and in the solid state by X-ray diffraction on single crystal, of a series of gallium(III) and indium(III) meso-mono(diethoxyphosphoryl)porphyrins bearing different peripheral substituents as well as the corresponding monoesters and phosphonic acids are reported. This work describes the first example of the X-ray structure of a self-assembled dimer formed via strong binding between the oxygen atom of the phosphonate substituent and the gallium(III) cations of adjacent porphyrin molecules [Ga-O = 1.9708(13) angstrom].
Crystal structure oftrans-dichloridobis[N-(5,5-dimethyl-4,5-dihydro-3H-pyrrol-2-yl-κN)acetamide]palladium(II) dihydrate
2017
The title complex, [PdCl2(C8H14N2O)2]·2H2O, was obtained by N–O bond cleavage of the oxadiazoline rings of thetrans-[dichlorido-bis(2,5,5-trimethyl-5,6,7,7a-tetrahydropyrrolo[1,2-b][1,2,4]oxadiazole-N1)]palladium(II) complex. The palladium(II) atom exhibits an almost square-planar coordination provided by twotrans-arranged chloride anions and a nitrogen atom from each of the two neutral organic ligands. In the crystal, N—H...O, O—H...O and O—H...Cl hydrogen bonds link complex molecules into double layers parallel to thebcplane.
Degradation of Amino-(3-methoxyphenyl)methanephosphonic Acid by Alternaria sp
2002
Alternaria sp. isolated from the surface of carrot ( Daucus carota ) seeds appeared to be able to degrade amino-(4-methoxyphenyl)-methanephosphonic acid using it as a sole source of carbon, nitrogen, and phosphorus for growth.
A morphometric comparison of dissimilar early development in sibling species of Platynereis (Annelida, Polychaeta)
1992
Early development of Platynereis massiliensis was studied in serial sections of fixed embryos and in living or fixed embryos whose nuclei had been made visible with a fluorescent label. The unfertilized egg is an ellipsoid with three axes of differing length. The longest axis corresponds to the dorsoventral axis of the developing embryo. Egg volume is ten times that in the sibling species, P. dumerilii, mainly due to increased yolk content. The timing and spatial pattern of cleavage were observed from first cleavage to the 62-cell stage. Volumes of the blastomeres, their nuclei, their yolk-free cytoplasm and their yolk were determined from serial sections up to the 29-cell stage. In the P. …
A facile cleavage of allyl ethers on solid phase
2000
Abstract A simple and efficient protocol for the cleavage of allyl ethers on solid phase using a palladium(0)-catalyzed allyl transfer reaction is reported.