Showing papers on "Double bond published in 1988"

Benzylic monooxygenation catalyzed by toluene dioxygenase from Pseudomonas putida

Abstract: Toluene dioxygenase, a multicomponent enzyme system known to oxidize mononuclear aromatic hydrocarbons to cis-dihydrodiols, oxidized indene and indan to 1-indenol and 1-indanol, respectively. In addition, the enzyme catalyzed dioxygen addition to the nonaromatic double bond of indene to form cis-1,2-indandiol. The oxygen atoms in 1-indenol and cis-1,2-indandiol were shown to be derived from molecular oxygen, whereas 70% of the oxygen in 1-indanol was derived from water. All of the isolated products were optically active as demonstrated by 19F NMR and HPLC discrimination of diastereomeric esters and by chiroptic methods. The high optical purity of (-)-(1R)-indanol (84% enantiomeric excess) and the failure of scavengers of reactive oxygen species to inhibit the monooxygenation reaction supported the contention that the monooxygen insertion is mediated by an active-site process. Experiments with 3-[2H]indene indicated that equilibration between C-1 and C-3 occurred prior to the formation of the carbon-oxygen bond to yield 1-indenol. Naphthalene dioxygenase also oxidized indan to 1-indanol, which suggested that benzylic monoxygenation may be typical of this group of dioxygenases.

Chemical modification in mass spectrometry IV—2-alkenyl-4,4-dimethyloxazolines as derivatives for the double bond location of long-chain olefinic acids

Abstract: Long-chain unsaturated fatty acids (UFA) can easily be converted on a microgram scale to the corresponding 2-alkenyl-4,4-dimethyloxazolines by condensation with 2-amino-2-methylpropanol (AMP). These modified molecules with a ‘hidden’ carboxyl group have been proved to be a class of useful derivatives for gas chromatography/mass spectrometry (GC/MS) of UFA mixtures. While possessing very good GC characteristics, the title compounds show regular, well-recognizable diagnostic ion peaks of the double bond position in the chain. Detailed description of the method as well as electron impact (E1) mass spectra of derivatives resulting from mono-, di and polyenoic (maximally containing six double bonds) acids are presented.

Organometallic Compounds Containing Oxygen Atoms

Abstract: Publisher Summary This chapter discusses the organometallic compounds containing oxygen atoms. At present, the range of organic ligands found in organometallic oxo compounds is quite restricted, the majority being either η-C 5 R 5 or alkyls or aryls having no β-hydrogen atom. Two basic routes to organometallic oxo compounds may be envisaged addition of an organic ligand to an inorganic oxo complex or addition of oxygen to an organometallic compound. Exhaustive decarbonylation with concomitant oxidation of a cyclopentadienyl metal carbonyl has proved to be a useful preparative route to cyclopentadienyl metal oxo compounds having no other ligands. In the ethylene complex, the oxo and ethylene ligands are cis to one another and the C–C axis of the ethylene is perpendicular to the M–O bond, a configuration that maximizes π bonding between the W(IV) (d 2 ) and the ethylene. Complexes containing cyclopentadienyl and oxygen as coligands are of two basic types: those containing a terminal double bond between a metal and oxygen, [M=O], and those containing one or more doubly bridging oxygen atoms, [M(μ 2 -O) n M]. The clusters are held together by M–O bonds and the M–( η 5 -C 5 H 5 ) bonding is of the usual type. Parallel to the development of organometallic clusters containing oxygen atoms has been the preparation of organometallic polyoxometallates. Although the organometallic groups are on the surface of the polyoxometallate, they are strongly and covalently bonded to the peripheral oxygen atoms.

Identification of the position and the stereochemistry of the double bond in monounsaturated fatty acid methyl esters by gas chromatography/mass spectrometry of dimethyl disulfide derivatives

Abstract: A single-step derivatization procedure using dimethyl disulfide (DMDS) is described for monounsaturated fatty acid esters (MUFAME). The analysis of DMDS adducts by gas chromatography/mass spectrometry is detailed: The mass spectra (electron impact 70 eV) show molecular ions (M/sup +/) and give key fragments that permit determination of the position of the original double bond. Alkylthiolation of Z- and E-MUFAME as a specific antiaddition leads, respectively, to the threo and erythro adducts. The two isomers are well-separated by gas chromatography, permitting precise stereochemistry of the initial double bond. Nevertheless, for a complex environmental mixture of MUFAME, the stereochemical identification is restricted to the linear series. This procedure is suitable for the analysis of trace compounds at the nanogram level such as encountered in the natural environment. An application is presented for the analysis of planktonic and bacterially derived fatty acids in recent marine sediments.

Steroid 5-alpha-reductase inhibitors

Abstract: Invented are 4-aza-5-alpha-8(14)-17 substituted-androsten-3-ones having an 8(14), 7(8), or 16(17) double bond, optionally also having a 1(2) double bond, pharmaceutical compositions containing the compounds, and methods of using these compounds to inhibit steroid 5-alpha-reductase.

Aziridination of alkenes catalysed by porphyrinirons: selection of catalysts for optimal efficiency and stereospecificity

Abstract: meso-Tetra-arylporphyriniron(III) derivatives catalyse the N-tosylaziridination of aryl-substituted styrenes by tosylimidoiodobenzene, PhlNTs, a nitrogen analogue of iodosylbenzene. Three secondary reactions were found to limit the yield of N-tosylaziridination: (i) the formation of toluene-p-sulphonamide, TsNH2, which is presumably derived from hydrolysis of a possible iron-nitrene, FeNTs, intermediate, (ii) the conversion of the Fe(TPP)(Cl)(TPP = tetraphenylporphyrin) catalyst into an iron(III) complex where the NTs moiety is inserted into an iron-nitrogen bond of Fe(TPP)(Cl), (iii) an oxidative degradation of the porphyrin catalyst. These secondary reactions were avoided to a great extent by using anhydrous conditions and Fe(TDCPP)(ClO4)(TDCPP = tetrakis-2,6-dichlorophenylporphyrin) as a catalyst instead of Fe(TPP)(Cl) and Fe(TPP)(ClO4). Under these conditions, N-tosylaziridination of styrene, cis- and trans-stilbene, and 1,1-diphenylethylene was performed with yields between 40 and 90%. Fe(TDCPP)(ClO4) was also found to be the best catalyst for N-tosylaziridination of aliphatic alkenes such as hex-1-ene, cyclo-octene, and cis-and trans-hex-2-enes. Although N-tosylaziridination of the two latter alkenes catalysed by Fe(TPP)(Cl) was not stereospecific, this reaction became stereospecific with Fe(TDCPP)(ClO4) as catalyst. These results show that by a proper choice of the porphyriniron catalyst, relatively good yields of N-tosylaziridination of alkenes by PhlNTs can be obtained. As for 1,2-disubstituted aliphatic alkenes, syn addition of the NTs moiety to the double bond takes place. A possible mechanism is presented.

Stopped-flow studies of the mechanisms of ozone-alkene reactions in the gas phase: trans-2-butene

Abstract: The reaction of ozone with trans-2-butene has been studied in the gas phase at 294 K and 530 Pa (4 Torr) by using a stopped-flow reactor coupled to a photoionization mass spectrometer. The concentrations of reactants and products were determined as a function of reaction time. A mechanism is proposed to account for the observed products: CH/sub 3/CHO, H/sub 2/CO, CO/sub 2/, CH/sub 4/, CH/sub 3/C(O)C(H)(OH)CH/sub 3/, H/sub 2/C/double bond/C/double bond/O, H/sub 2/O, 2-butanone, 2,3-epoxybutane, CH/sub 3/C(O)C(O)CH/sub 3/, and HC(O)C(O)H. This work again indicates that the simple hot ester hypothesis needs to be critically reconsidered for gas-phase ozonolysis.

Imide derivatives, their production and use

Abstract: A compound of the formula: wherein A is a carbonyl group or a sulfonyl group; B is either one of the formulas: (in which E is a methylene group, an ethylene group or an oxygen atom and a full line accompanying a broken line (....) indicates a single bond or a double bond), , (in which F is a methylene group or an ethylene group and afull line accompanying a broken line (....) is as defined above)and (in which R1, R2, R3, R4, RS and R6 are each a hydrogen atom or a methyl group) when A represents a carbonyl group, or B is a 1,2-phenylene group when A represents a sulfonyl group; D is an ethylene group, an ethenylene group or an ethynylene group, of which one or more may be optionally substituted with hydroxyl; and n is an integer of 0,1 or 2, or its acid addition salts, which is useful for treatment of psychosis.

Radical Cyclization in the Control of Regio- and Stereochemistry

Abstract: This article presents a review of the control of regio- and stereochemistry which is now possible by the use of the recently introduced haloacetal and the related halosilyl ether cyclizations, starting from a cyclohexenol or a cyclopentenol. The hydroxyl group is the control element which permits the addition of two carbon chains to the double bond of the allylic alcohol system, with complete regiospecificity and stereospecificity at the near end of the double bond, and with complete regiospecificity and high stereoselectivity at the far end of the bond. Examples of the use of the new methodology from the field of alkaloid, steroid and prostaglandin synthesis are given.

Synthesis and chemistry of a dinuclear iridium bis-.mu.-oxo complex. Observation of oxygen transfer and phosphorus-carbon bond cleavage

Abstract: Much attention has been recently directed toward the possible role of reactive transition-metal oxo complexes as oxidizing and oxygen-atom-transfer agents. The synthesis and chemical reactions of dinuclear iridium {mu}-oxo complexes capable of oxygen atom transfer and reaction with C-H bonds are reported herein. The complexes were characterized by proton, {sup 13}C, {sup 31}P NMR spectra (where applicable), infrared and mass spectrometry and elemental analysis. 18 refs.

Characterization of HETEs and related conjugated dienes by UV spectroscopy.

Abstract: Three distinct pairs of HETEs can be distinguished on the basis of their UV spectra. We used hydroxy-linoleates (hydroxy-octadeca-cis-trans-dienoates) as a base for comparisons; both the 9- and 13-hydroxy isomers have identical chromophores with λmax near 234 nm. The presence of a double bond three carbons removed from the conjugated diene (the chromophore of 9- and 11-HETE) causes a shift in the observed λmax to near 235 nm. A double bond β to the chromophore (5- and 15-HETE) gives a further shift of 1.5 nm, giving a λmax between 236–236.5 nm. With double bonds in both these positions (8- and 12-HETE), the λmax is observed near 237 nm. It is apparent that the exact λmax of thecis-trans diene chromophore is influenced in a consistent way by the adjacent methylene interruptedcis double bonds.

Heterogeneous acid-catalyzed amination of isobutene to tert-butylamine

Abstract: Ammonia (II) is added to the double bond of isobutene (I) in the presence of a zeolite catalyst to give tert-butylamine (III).

Computational evaluation and comparison of some nitramine properties

Abstract: A computational study of six nitramines, R/sub 1/R/sub 2/NNO/sub 2/, has been carried out with the objective of gaining a better understanding of how the properties of the NNO/sub 2/ group are affected by the natures of R/sub 1/ and R/sub 2/. An ab initio SCF procedure was used, with the initial step being the determination of each molecule's optimized geometry. This was subsequently used to compute its bond orders, dipole moment, and electrostatic potential. In most instances, the NNO/sub 2/ portions of the molecules are planar, due to the strong electron-withdrawing effect of the nitro group; the amino-type nitrogen can better respond to this when in a planar configuration. One consequence is that the N-NO/sub 2/ bonds possess some degrees of double bond character; their bond orders range from 1.36 to 1.63, with the weaker bonds corresponding to the more electron-withdrawing R/sub 1/ and R/sub 2/ groups. The strong negative electrostatic potentials normally associated with the lone pairs of amino-type nitrogens are greatly weakened or eliminated in most of these molecules; several of them show evidence of significant hyperconjugation, resulting in enhanced acidic character.

Double bond oxidation of unsaturated fatty acids

Abstract: Different oxidizing agents for performing the cleavage oxidation of the double bond of the unsaturated fatty acids are presented, and their economic performance is analyzed. Ozone and sodium hypochlorite are the most commercially efficient oxidants.

Vanadium tetrachloride stabilization

Abstract: Solutions of VCl₄ in inert organic solvent are stabilized by incorporation of decomposition retardants being halogenated organic compounds having at least two halogen atoms attached to the same carbon atom and activated by adjacent electron donor groups or carbon-carbon double bonds. One of the especially preferred stabilizers is butyl perchlorocrotonate. The solutions are useful in polymerization processes.

Process for making a thermoplastic resin composition

Abstract: A process for making a thermoplastic resin composition which comprises melting and mixing 100 parts by weight of polyphenylene ether (A) and 0.01 - 5.0 parts by weight of at least one compound (B) which contains in its molecule both (a) carbon-carbon double bond or carbon-carbon triple bond and (b) carboxyl group, acid anhydride group, acid amide group, imide group, carboxylic acid ester group, epoxy group, amino group or hydroxyl group in the presence of 0.01 % or more and less than 0.1 % by weight of radical initiator based on the polyphenylene ether (A), said polyphenylene ether (A) being obtained by oxidation-polymerization of at least one phenol com­pound represented by the formula: wherein R₁, R₂, R₃, R₄ and R₅ represent a hydrogen atom, a halogen atom, a hydrocarbon or a substituted hydro­carbon group, with a proviso that at least one of them is a hydrogen atom, and said polyphenylene ether (A) having a reduced viscosity η sp/c of 0.40 - 0.58 deciliter/gram.