Showing papers on "Double bond published in 1986"

Preparation and structure of a stable molecule containing a silicon nitrogen double bond and of its tetrahydrofuran adduct

Abstract: The pale yellow, solid silaketimine But2N–SiBut3 has been prepared and structurally characterized [SiN 1.568(3)A, Si–N–Si 177.8(2)°]; it forms a stable adduct with tetrahydrofuran by complexation of the unsaturated silicon atom.

Photolysis of the nitrogen-nitrogen double bond in trioxodinitrate: reaction between triplet oxonitrate(1-) and molecular oxygen to form peroxonitrite

Abstract: Etude de la decomposition photochimique du trioxodinitrate; l'intermediaire reactif NO − peut apparaitre dans les etats singulet et triplet. Cinetique d'ordre 0

Gas-phase studies of alkene oxidation by transition-metal oxides. Ion-beam studies of CrO+

Abstract: An examination of reaction thermochemistry and metal oxide bond dissociation energies focuses attention on the chromium oxide ion as an interesting candidate for investigations of hydrocarbon oxidation processes. Reactions of this species, formed by surface ionization, have been examined with ion-beam reactive scattering techniques. In reactions with alkenes, CrO⁺ abstracts allylic hydrogen to form CrOH⁺ and adds to double bonds to yield aldehydes and other products which are rationalized by postulating metallacyclic intermediates. In comparison with other first-row transition-metal oxides, which are either too stable (Sc, Ti, and V) or too reactive (Mn, Fe, Co, and Ni), CrOAn examination of reaction thermochemistry and metal oxide bond dissociation energies focuses attention on the chromium oxide ion as an interesting candidate for investigations of hydrocarbon oxidation processes. Reactions of this species, formed by surface ionization, have been examined with ion-beam reactive scattering techniques. In reactions with alkenes, CrO⁺ abstracts allylic hydrogen to form CrOH⁺ and adds to double bonds to yield aldehydes and other products which are rationalized by postulating metallacyclic intermediates. In comparison with other first-row transition-metal oxides, which are either too stable (Sc, Ti, and V) or too reactive (Mn, Fe, Co, and Ni), CrO⁺ exhibits a balance in being reactive but selective. Bond dissociation energies derived in this study include Z) An examination of reaction thermochemistry and metal oxide bond dissociation energies focuses attention on the chromium oxide ion as an interesting candidate for investigations of hydrocarbon oxidation processes. Reactions of this species, formed by surface ionization, have been examined with ion-beam reactive scattering techniques. In reactions with alkenes, CrO⁺ abstracts allylic hydrogen to form CrOH⁺ and adds to double bonds to yield aldehydes and other products which are rationalized by postulating metallacyclic intermediates. In comparison with other first-row transition-metal oxides, which are either too stable (Sc, Ti, and V) or too reactive (Mn, Fe, Co, and Ni), CrO⁺ exhibits a balance in being reactive but selective. Bond dissociation energies derived in this study include D°(Cr⁺-O) = 85.3 ± 1.3 kcal mol⁻¹ and D°(Cr-O) = 110 ± 2 kcal mol⁻¹.

Ternary carbides of the rare earth and iron group metals with CeCoC2- and CeNiC2-type structure

Abstract: 32 carbides RTC2 (R ≡ rare earth metal, T ≡ Fe, Co, Ni), 18 for the first time, were prepared by arc melting of the elemental components and subsequent annealing in evacuated silica tubes. Most of them crystallize in the orthorhombic CeNiC2-type structure. The carbides LnCoC2 (Ln ≡ La, Ce, Pr, Nd) have the related monoclinic CeCoC2-type structure. SmCoC2 is of CeCoC2 type at low temperature and of CeNiC2 type at high temperature. The crystal structures of DyCoC2 and DyNiC2 were refined from singlecrystal X-ray data to residuals of R = 0.012 (581 structure factors) and R = 0.023 (971 structure factors) for 17 variable parameters. The carbon atoms in these compounds form pairs. The C-C distances of 1.37 A come close to the double bond distances of 1.34 A in alkenes. The hydrolysis of DyCoC2 in diluted hydrochloric acid, however, yields only little ethene, mainly ethane and some propane and methane. The cell volumes indicate that cerium and ytterbium are essentially trivalent in these compounds, whereas the corresponding europium compounds cannot be prepared under similar conditions.

Novel cobalt(II)-catalyzed oxidative cleavage of a carbon-carbon double bond

Abstract: Oxydation de l'isoeugenol en presence de [bis (salicylideneamino-3 propyl) methyl amine] cobalt(II)

Topical compositions intended for skin treatment containing salicylic acid derivatives

Abstract: Topical compositions intended for skin treatment and based on salicylic acid derivatives The invention relates to topical compositions with a keratolytic and/or comedolytic effect, containing, in a carrier which is suitable for application to skin, at least one compound corresponding to the formula I: ##STR1## in which R denotes a linear, branched or cyclized saturated aliphatic chain containing from 3 to 11 carbon atoms, an unsaturated chain containing from 3 to 17 carbon atoms and containing one or more conjugated or unconjugated double bonds, these various substituents being optionally substituted by one or more halogen atoms, by one or more trifluoromethyl groups, by one or more hydroxyl groups in free form or esterified with an acid containing from 1 to 6 carbon atoms or by a carbonyl group which is free or esterified with a lower alcohol containing from 1 to 6 carbon atoms, R' denotes a hydroxyl group or an ester group of formula: ##STR2## where R 1 denotes a saturated or unsaturated aliphatic group containing from 1 to 18 carbon atoms

Direct addition of elemental fluorine to double bonds

Abstract: Fluoration de stilbene, cinnamate d'ethyle, cycloheptene, cyclododecene, octene-1, dodecene-1, coumarine. Les composes difluores obtenus proviennent d'une addition syn

Cobalt-mediated [2 + 2 + 2] cycloadditions of alkynes to the indole 2,3-double bond: an extremely facile entry into the novel 4a,9a-dihydro-9H-carbazole nucleus

Abstract: Because of the extremely diverse physiological activity exhibited by the indole nucleus and its presence in a multitude of natural products selective alteration of its structure has commanded a considerable amount of synthetic attention. Part of this effort has involved the utilization of the 2,3-double bond in Diels-Alder and other cycloadditions. The authors report a novel mode of reactivity of this bond in the presence of eta-CpCo reagents: the (2 + 2 + 2) cycloaddition to two alkynes to provide the hitherto unknown 4a,9a-dihydro-9H-carbazole nucleus as incorporated in a variety of complex polycyclic dienes. This methodology demonstrates for the first time the feasibility of activating aromatic double bonds in CpCo-mediated cyclizations and provides a powerful means by which to fuse several rings onto the indole moiety in one step.

Substituent effects on neutral and ionized carbon-carbon and carbon-oxygen double bonds and their implications for the stability order of keto/enol tautomers

Abstract: On etudie par des calculs d'orbitales moleculaires ab initio les effets des substituants sur des molecules d'ethylene ou de formaldehyde monosubstituees, neutres ou cationiques

Bonding in transition-metal-methylene complexes. 2. (RuCH2)+, a complex exhibiting low-lying methylidene-like and carbene-like states.

Abstract: The electronic structure of a representative late-transition-metal-methylene complex, Ru=CH/sub 2//sup +/, has been studied by ab initio methods (generalized valence bond/configuration interaction). The electronic-state spectrum reveals five states close in energy (spread of 12.9 kcal/mol) that partition into two groups in terms of energy separation and mode of metal-carbon bonding. The ground state has /sup 2/A/sub 2/ symmetry and contains covalent M-C sigma and ..pi.. bonds (metal-methylidene); a /sup 2/A/sub 1/ state of the same bond character is only 1.2 kcal/mol higher. A cluster of three degenerate excited states (/sup 4/A/sub 2/, /sup 4/B/sub 1/, and /sup 4/B/sub 2/) 12.9 kcal/mol above the ground state exhibits completely different bonding character, namely, sigma-donor/..pi..-acceptor M-C bonds are formed (metal-carbene). We conclude that for highly unsaturated, late-transition-metal systems, metal-carbene bonding may be competitive with metal-alkylidene bonding, leading to donor/acceptor bonds comparable in strength to that of covalent double bonds.

Electrically conducting polymers.

Abstract: An electrically conducting organic material for use on battery electrodes and the like, which comprises a polymer optionally doped with an n- or p-type dopant, wherein the polymer contains along its backbone at least one pi-conjugated linear unit of formula (I), wherein A is a divalent optionally-substituted conjugated organic cyclic group containing a pi-conjugated sequence of single bonds and at least two double bonds; B is a tetravalent optionally-substituted conjugated organic cyclic group containing a pi-conjugated sequence of single bonds and at least one double bond; A and B have the same molecular and structural formula except that they contain a different configuration of double and single bonds; Y is a trivalent group containing m linking atoms between adjacent groups A and B where m is an odd number from 1 to 11, provided that when Y contains more than one linking atom between said adjacent groups, the linking atoms form a pi-conjugated chain of atoms between said adjacent groups A and B, and n is an integer from 1 to 4. One example of the material is poly(2,2'-dipyrrylmethane) doped with CF3SO3 ions, which is relatively air- and water-stable and has a conductivity of about 1.0S cm-1.

Samarium-mediated functionalization of N=N bonds: double insertion of carbon monoxide into the N=N bond of azobenzene

Abstract: The insertion of carbon monoxide into a metal-carbon bond and olefin metathesis are two fundamental reactions in organometallic chemistry. These reactions and their analogues are central to many important stoichiometric and catalytic organometallic transformations. The authors have recently discovered a new samarium(II)-based reaction which combines CO activation and the multiple-bond breaking and making typical in metathesis reactions. They describe this remarkable transformation in which an N=N double bond is broken and two N-C bond and a C-C bond are formed in a single reaction.

Antiparasitic avermectin and milbemycin derivatives and process for their preparation

Abstract: The invention provides novel compounds having the formula: wherein the broken line at the 22-23 position represents an optional double bond and wherein R' is H or OH and the double bond is absent, or, the double bond is present and R' is absent; R2 is an alpha-branched C3-C8 alkyl, alkenyl, alkynyl, alkoxyalkyl or alkylthioalkyl group; a C3-C8 cycloalkyl, C5-C8 cycloalkenyl or C5-C8 cycloalkylalkyl group, any of which may optionally be substituted by methylene or one or more C1-C4 alkyl groups or halo atoms; or a 3 to 6 membered oxygen or sulphur containing heterocyclic ring which may optionally be substituted by one or more C1-C4 alkyl groups or halo atoms; R3 is hydrogen or methyl; R4 is H or 4'-(alpha-L-oleandrosyl)-alpha-L-oleandrosyloxy, with the proviso that when R2 is alkyl it is not isopropyl or sec-butyl, and when R4 is H, R1 is OH, and the double bond is absent, R2 is not 2-buten-2-yl, 2-pentene-2-yl or 4-methyl-2-pentene-2-yl. The compounds are broad spectrum antiparasitic agents having utility as anthelmintics, ectoparasiticides, insecticides and acaricides. The invention also provides a process for producing the novel avermectin and milbemycin derivatives by adding a carboxylic acid or derivative thereof to a fermentation of an avermectin or milbemycin producing organism.

Hydrogenation of polymer

Abstract: PURPOSE: To impart weather resistance, oxidation resistance, etc., to a conjugated diene (co)polymer, by contacting it with hydrogen in the presence of a specified catalyst in an inert organic solvent to thereby selectively hydrogenate the unsaturated double bonds in the conjugated diene units of the polymer. CONSTITUTION: A (co)polymer is prepared by polymerizing a conjugated diene such as 1,3-butadiene or isoprene, or by copolymerizing a diene with a vinyl- substituted aromatic hydrocarbon (e.g., styrene). The resulting (co)polymer is contacted with hydrogen under a mild hydrogenation condition in an inert organic solvent in the presence of a catalyst comprising bis(cyclopentadienyl)titanium dichloride and an alkyllithium compound of the formula: R-Li (wherein R is a 1W6C alkil), e.g., n-butyllithium or isopropyllithium, to thereby selectively hydrogenate the unsaturated double bonds in the conjugated diene units of the (co)polymer. COPYRIGHT: (C)1984,JPO&Japio

Process for extractive fermentation

Abstract: A process for producing a variety of chemical products, e.g., ethanol, by fermentation in which the product is removed from the fermentation medium as it is formed by liquid-liquid extraction using an extractant for the product which is immiscible with water. The extractant employed is chosen from the following groups: (A) double bond unsaturated aliphatic alcohols having 12 or more carbon atoms; (B) saturated branched chain aliphatic alcohols having 14 or more carbon atoms or mixtures thereof; (C) double bond unsaturated aliphatic acids having 12 or more carbon atoms; (D) aliphatic and aromatic mono-, di- or tri-esters having 12 or more carbon atoms, other than dibutyl phthalate; (E) aliphatic noncyclic ketones and aliphatic aldehydes having 12 or more carbon atoms; and (F) mixtures of extractants from groups (A) to (E) above or mixtures of at least one of the above extractants and at least one other extractant. These extractants are non-toxic to microorganisms used for fermentation, have little tendency to form emulsions and are otherwise suited for the process. The liquid-liquid extraction may thus be carried out in situ in the fermentor, preferably in a continuous stirred tank fermentor.

Barriers to rotation adjacent to double bonds. 2. n-Propyl versus isopropyl groups

Abstract: The barriers to rotation about the C-C bonds adjacent to the carbonyl groups of isobutyraldehyde, methyl isopropyl ketone, and isobutyric acid were calculated. The 3-21G basis set was used for the geometry optimizations, and the 6-31G* basis set was used to obtain the energies. The differences in energy between R = n-propyl and isopropyl also were calculated and reproduced the observed energy differences. Whereas the more branched isomer had a significantly lower energy for the aldehydes and acids, the difference in energy was very small with the ketones. The components of the barrier are discussed. The traditional decomposition into 1-, 2-, and 3-fold terms does not provide a useful representation of the interactions which are involved. Besides the 3-fold barrier observed with compounds having R = CH3, the major contributions to the barrier arise from the stabilizing interaction between an alkyl group and the carbonyl (- 1 kcal/mol) and from the repulsive interaction between one of the methyls of the isopropyl group and the other substituent at the carbonyl. A hydroxy group (Le., in a carboxylic acid) leads to a significantly smaller steric interaction than found with a methyl group (i.e,, in a methyl alkyl ketone).