Showing papers on "Double bond published in 1972"
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TL;DR: In this article, the use of different spectra (UV, visible and NMR spectra) for the identification of polycyclic hydrocarbons was demonstrated for the first time.
Abstract: The use of different spectra (UV, visible and NMR spectra) is demonstrated for the identification of polycyclic hydrocarbons.
960 citations
TL;DR: The basic chemistry of the reaction is investigated and the reactivity of this single reagent with various lipids is determined, suggesting that it requires a carbon-carbon double bond.
Abstract: Results with the "sulfo-phospho-vanillin" reaction, much used for determining total serum lipids, have been favorably compared with those for the gravimetric method. We investigated the basic chemistry of the reaction and determined the reactivity of this single reagent with various lipids. Our results suggest that: ( a ) The reaction requires a carbon-carbon double bond. ( b ) Concentrated sulfuric acid reacts with unsaturated lipids in the initial step to form a carbonium ion. ( c ) Phosphoric acid reacts with vanillin to produce a phosphate ester, with a resulting increase in the reactivity of the carbonyl group. ( d ) The carbonium ion reacts with the carbonyl group of phosphovanillin to form a colored compound, which is stabilized by resonance. ( e ) Unsaturated compounds with more than one double bond react, but reaction may vary with steric hindrance. ( f ) The method is reasonably precise, but its accuracy depends primarily on the reference standard used.
491 citations
TL;DR: The unsaturation and the distribution of the double bonds appear to be of critical importance for the barrier properties of lecithins and for the interaction with cholesterol.
320 citations
TL;DR: In this article, the carboxy-group of a series of substituted N-methylmaleamic acids is shown to be remarkably sensitive to the pattern of substitution on the carbon-carbon double bond.
Abstract: The efficiency of intramolecular catalysis of amide hydrolysis by the carboxy-group of a series of substituted N-methylmaleamic acids is remarkably sensitive to the pattern of substitution on the carbon–carbon double bond. A single alkyl group increases the rate of hydrolysis by a factor which increases with its size. A second alkyl substituent has a disproportionately larger effect, which is sharply reduced when the two groups are joined together in a ring. The rates of hydrolysis of a series of dialkyl-N-methylmaleamic acids range over more than ten powers of ten, and the ‘effective concentration’ of the carboxy-group of the most reactive compound studied is greater than 1010M. This amide, dimethyl-N-n-propylmaleamic acid, is converted into the more stable dimethylmaleic anhydride with a half-life of less than 1s at 39 °C below pH 3. The mechanism of catalysis, and the factors responsible for this extremely high reactivity, are discussed.
154 citations
TL;DR: In contrast to the singleβ′-form generally attributed to such triglycerides, at least two intermediate endotherms were found for most samples between the least stable (α) and most stable (β) polymorphs as discussed by the authors.
Abstract: The polymorphism of 13 single acid triglycerides with acyl group chain lengths ranging from 16–22 was studied by differential scanning calorimetry. In contrast to the singleβ′-form generally attributed to such triglycerides, at least two intermediate endotherms were found for most samples between the least stable (α) and most stable (β) polymorphs. For saturated triglycerides, two versions of the familiar “tuning fork” model meet theβ′-form requirement of alternate fatty acid chains in planes perpendicular to each other. The detection of three intermediate endotherms for triolein, tri-cis-1 1-octadecenoin and trierucin (and possibly also trilinolein) may be rationalized by assuming that the segments of polymethylene chains on either side of double bonds may zigzag in different planes. Four exceptions for which no evidence was found forβ′-forms are tri-cis-6-octadecenoin, tri-cis-6-hexadecenoin, tri-trans-6-octadecenoin and trielaidin. Three of these exceptions contain Δ6-acyl groups and have in common segments with even numbers of methylene groups on either side of the double bonds. These same three triglycerides also have a shorter than usual polymethylene segment between the ester linkages and the double bonds and a longer than usual distance from the double bonds to the terminal methyl groups. Tri-trans-6-octadecenoin and trielaidin are exceptional in still another way. Only they and are exceptional in still another way. Only they and trierucin exhibited significant nonconformity with an empirical relationship between melting points and heats of fusion ofβ-forms. Otherwise, all points in a plot of the former physical constants vs. the latter closely fit a smooth curve, the positive slope of which gets larger as the X-axis values, i.e., melting points, increase.
111 citations
TL;DR: In this article, six new compounds, named litsenolides A1, A2, B1, B2, C1 and C2, have been isolated from the roots of Litsea japonica.
98 citations
TL;DR: In this article, the PE-spectra of 8-isopropylidene-tricyclo[3.02,4]-octane and the corresponding octene was analyzed, and it was shown that the π-orbital πc of the exocyclic double bond conjugates more strongly with the symmetric Walsh-orbitals of the cyclopropano moiety than with the double bond in the same position.
Abstract: A method outlined previously [1] is used to show that in norbornadiene (3) the b2(π) orbital lies above a1(π), as predicted by theory. This indicates that in 3 through-space interaction between the two basis π-orbitals πa and πb is more important than through-bond interaction.
Analysis of the PE.-spectra of 8-isopropylidene-tricyclo[3.2.1.02,4]-octane (13) and the corresponding octene (15) confirms that the π-orbital πc of the exocyclic double bond conjugates more strongly with the symmetric Walsh-orbital es of the cyclopropano moiety than with the π-orbital πa of a double bond in the same position.
91 citations
80 citations
60 citations
TL;DR: The results indicate that triple bonds and cis double bonds inhibit a relatively ordered packing of lipid alkyl chains in the region between unsaturated sites and terminal methyl groups, leaving the hydrophobic region bounded by acyl groups and uns saturated sites unaffected.
Abstract: Cultures of a yeast mutant, deficient in the synthesis of unsaturated fatty acids, were supplemented with either stearolic acid or with any one of three octadecanoic acids having a cis double bond 6, 9, or 11 carbons away from the acyl group. The resulting cells, with lipid alkyl chains well defined with respect to the position and nature of unsaturated sites, were then studied with spin-labeled stearic acids having a N-oxyloxazolidine ring located at 4, 6, 9, or 12 carbons away from the acyl group, and added in vitro to the cellular preparations. Differences in the molecular motion of each spin label were observed, as a function of the unsaturated site, in the intact yeast cells. Characteristic order to disorder phase transitions are inferred from data of temperature dependence. The results also indicate that triple bonds and cis double bonds inhibit a relatively ordered packing of lipid alkyl chains in the region between unsaturated sites and terminal methyl groups, leaving the hydrophobic region bounded by acyl groups and unsaturated sites unaffected.
55 citations
TL;DR: A membrane-bound oleyl coenzyme A desaturase from maturing Carthamus tinctorius seeds specifically catalyzed the conversion of oleyL-CoA to linoleyl- CoA, suggesting that DPNH did not interact directly with molecular oxygen and the desaturases but served only as a source of electrons.
TL;DR: In this paper, the isomerized double bond α,β to the hydro-peroxide group at carbon-13 was determined to be betrans and the complete structures of the major products proved to be 13-hydroperoxy-cis-9,trans-11-deca-decadienoic acid from linoleic and linolenic acids with soybean lipoxygenase.
Abstract: Hydroperoxides produced by oxidation of linoleic and linolenic acids with soybean lipoxygenase were analyzed by nuclear magnetic resonance. The isomerized double bond α,β to the hydro-peroxide group at carbon-13 was determined to betrans. The complete structures of the major products proved to be 13-hydroperoxy-cis-9,trans-11-octa-decadienoic acid from linoleic acid and 13-hydroperoxy-cis-9,trans-11,cis-15-octadecatrienoic acid from linolenic acid. The configuration of the double bonds indicates that oxidation took place through a free radical mechanism as proposed previously by others.
TL;DR: The reason for the instability of simple transition metal alkyls, M(CH2SiMe3) generally is to be sought in the available possible pathways for decomposition reactions of the alkyl chain alkene and/or alkane elimination reactions.
Abstract: On account of the apparent instabilities or difficulties in isolating simple alkyls of transition metals it has commonly been assumed firstly that the bond strength is low and secondly that the presence of it-acid ligands such as CO, R3P, it-C5H5, etc. on the metal are necessary for the existence of stable metal— carbon cr-bonds. Although only a few bond strengths have been estimated, and these in compounds with other ligands present, there is no sound reason for assuming that the metal to carbon bond strengths are low. The reason for the instability of simple transition metal alkyls, M—R, generally is to be sought in the available possible pathways for decomposition reactions of the alkyls such as hydrogen transfer from a or 3-carbon atoms of the alkyl chain alkene and/or alkane elimination reactions, etc. The synthesis of elimination—stabilized alkyls of transition metals in high oxidation states is discussed and illustrated primarily by consideration of trimethylsilylmethyl derivatives, from which alkene elimination is impossible due to the incapacity for forming silicon to carbon double bonds. The chemical properties and structures of compounds M(CH2SiMe3) where M =yIV, Cr', Mo", W" etc., and of other related species are described together with appropriate infrared, nuclear magnetic resonance and electron spin resonance
TL;DR: In this article, α-chloronitrones were introduced as precursors of a new class of reagents that undergo an Ag+-induced reaction with unactivated olefins with great ease to give products considered to result from 1,4-cycloadditions of N-alkyl-N-vinyl-nitrosonium ions to the carbon-carbon double bond.
Abstract: Organic synthesis may be said to be in need of enophiles, i.e. reagents that would undergo cycloaddition reactions with any isolated olefinic double bond, in contrast to most of the classical Diels-Alder or 1,3-dipolar addition reagents which, as a rule, require activated olefins in order to participate smoothly in cycloaddition processes. This paper introduces α-chloronitrones as precursors of a new class of such reagents; they undergo an Ag+-induced reaction with unactivated olefins with great ease to give products considered to result from 1,4-cycloadditions of N-alkyl-N-vinyl-nitrosonium ions to the carbon-carbon double bond (see scheme 2). This process is believed to have a number of synthetic applications, two of them being illustrated in two subsequent communications.
TL;DR: In trifluoroacetic acid, protonation of (2,3,4,5,tetrahapto-cycloheptatrienone)tricarbonyliron is stereoselective and occurs from the exo side of the ring at a coordinated double bond [C(2] as mentioned in this paper.
TL;DR: In this article, the central CC double bond of nucleophilic carbenes is cleaved with β elimination to give open-chain compounds, including CH-acidic compounds and compounds containing NH or OH groups.
Abstract: Proton-active substances react with certain electron-rich olefins with cleavage of the central CC double bond to give compounds that can be formally regarded as insertion products of nucleophilic carbenes. If they satisfy certain structural conditions, they isomerize with β elimination to give open-chain compounds. Both CH-acidic compounds and compounds containing NH or OH groups can undergo this reaction. The mechanisms are discussed, and the importance of the intermediate products to biochemistry (thiamine, tetrahydrofolic acid) is indicated.
TL;DR: In this article, the products from cycloaddition of benzonitrile 4-nitrobenzylide were structurally elucidated to the CN triple bond (ethyl cyanoformate, aryl cyanate), the CN double bond and the CS double bond.
Abstract: Die Cycloaddukte des Benzonitril-[4-nitro-benzylids] (2) an die CN-Dreifachbindung (Cyanameisensaureester, Aryl-cyanat), die CN-Doppelbindung (N-Benzyliden-methylamin) und die CS-Doppelbindung (Dithiobenzoesaureester, Thionbenzoesaureester, Trithiokohlensaureester, Thionkohlensaureester) werden strukturell gesichert. Der Anlagerung an Nitrosobenzol folgt eine Cycloreversion zu Nitron – Nitril. Die bei den Nitril-ylid-Cycloadditionen beobachteten Orientierungen werden mit denen des Diphenylnitrilimins und der Diazoalkane verglichen.
1.3-Dipolar Cycloadditions, 64. Further Reactions of Nitrile Ylides with Hetero-multiple Bonds
The products from cycloaddition of benzonitrile 4-nitrobenzylide (2) to the CN triple bond (ethyl cyanoformate, aryl cyanate), the CN double bond (benzylidenemethylamine) and the CS double bond (methyl dithiobenzoate and thionbenzoate, trithiocarbonic and thioncarbonicester) were structurally elucidated. The addition to nitrosobenzene is followed by a cycloreversion to give nitrone – nitrile. Nitrile ylides, nitrile imines and diazoalkanes are compared in their directions of cycloaddition.
TL;DR: It is suggested that the conformation and structure of the CoA derivatives of these acids is such that they can irreversibly occupy the site on the enzyme responsible for 9,10-desaturation.
Abstract: Four cyclopropene fatty acids, having the double bond of the cyclopropene ring at the 8,9, 9,10, 10,11 and 11,12 positions, respectively, were tested as inhibitors of stearic acid desaturation by the desaturase enzyme system of hen liver. The first three were powerful inhibitors, but the last was not. The cyclopropene acids with the 9,10 and 10,11 double bonds were equally strong inhibitors, while the acid with the 8,9 double bond was less effective. To account for the specificity of those cyclopropene fatty acids in which the C9 or C10 carbon atom is included in the cyclopropene ring, it is suggested that the conformation and structure of the CoA derivatives of these acids is such that they can irreversibly occupy the site on the enzyme responsible for 9,10-desaturation.
TL;DR: In this article, a line shape treatment based on the Bloch formalism has been used to assign sites to methyl groups with the aid of aromatic solvent induced shifts and anisotropy effects.
Abstract: 1, 1-Bis-dimethylaminoethylenes with electron attracting substituents on C2 show rotations around the CC and CN bonds, the rates of which are in most cases measurable by the NMR line shape method. The temperature-dependent four-and eight-site NMR spectra have been analysed and the barriers to rotation around the different bonds have been evaluated by a complete line shape treatment based on the Bloch formalism. Assignment of sites to methyl groups has been made with the aid of aromatic solvent induced shifts and anisotropy effects.
TL;DR: In this paper, the authors demonstrate the mechanistic consequences of level ordering in a given molecule on its reactivity, using the recently synthesized hypostrophene, which contains two CC double bonds in a rigid, cisoid conformation, as an example.
TL;DR: Perfluoroheptylcopper with 1-heptene and 1-dodecene gives mixtures of 1-(perfluorohexene)cycloalkane whereas cyclopentene yields only the olefin this paper.
TL;DR: In this paper, the branching reaction in the radical polymerization of vinyl acetate was studied kinetically, and the chain-transfer constants to the main chain and to the acetoxy methyl group (Cp,1) on the polymer were calculated on the basis of the experimental data described in the preceding paper.
Abstract: The branching reaction in the radical polymerization of vinyl acetate was studied kinetically. Branching occurs by polymer transfer as well as terminal double-bond copolymerization. The chain-transfer constants to the main chain (Cp,2) and to the acetoxy methyl group (Cp,1) on the polymer were calculated on the basis of the experimental data described in the preceding paper giving Cp,2 = 3.03 × 10−4, Cp,1 = 1.27 × 10−4 at 60°C, and Cp,2 = 2.48 × 10−4, Cp,1 = 0.52 × 10−4 at 0°C. Chain transfer to monomer is important with respect to the formation of the terminal double bond. The total values of transfer constants to the α- or β-position in the vinyl group and the acetoxymethyl group in vinyl acetate was determined to be 2.15 × 10−4 at 60°C. The transfer constant to the acetyl group in the monomer (Cm,1) was also evaluated to be 2.26 × 10−4 at 60°C from the quantitative determination of the carboxyl terminals in PVA. These facts suggest that the chain-transfer constant to the α- or β-position in the monomer (Cm,2) is nearly equal to zero within experimental error. Copolymerization reactivity parameters of the terminal double bond were also estimated. In conclusion, it has become clear that the formation of nonhydrolyzable branching by the terminal double-bond reaction can be almost neglected, and hence that the long branching in PVA is formed only by the polymer transfer mechanism. On the other hand, a large number of hydrolyzable branches in PVAc are prepared by the terminal double-bond reaction rather than by polymer transfer.
TL;DR: In this article, the torsional angles about the 1-α single bond and about the α-α double bond in hindered stilbene derivatives were calculated for the ground and for the excited states.
TL;DR: Stereochemical assignments have been made to the cyclopropyl ketones obtained from 3-benzylidenechroman-4-ones by their reaction with dimethylsulphoxonium methylide as mentioned in this paper.
Abstract: Stereochemical assignments have been made to the cyclopropyl ketones obtained from 3-benzylidenechroman-4-ones by their reaction with dimethylsulphoxonium methylide The effect of increasing the steric hindrance at the α-position of the double bond on the course of the reaction has been noted and the predominant formation of one isomer is attributed to the steric effect of a ring carbonyl group having an adjacent anionic centre
TL;DR: In this paper, the crystal structure of all-trans 1,5,9-cyclododecatrienenickel, C12H18Ni, has been determined from three-dimensional X-ray data collected at room temperature by counter methods.
TL;DR: The enaminoid derivatives formed by deprotonation of the olefin-α-chloro-nitrone cycloadducts undergo a beautifully clean cycloreversion at ambient or slightly elevated temperatures.
Abstract: The enaminoid derivatives formed by deprotonation of the olefin-α-chloro-nitrone cycloadducts (see preceding communications) undergo a beautifully clean cycloreversion at ambient or slightly elevated temperatures. The sequence (2+4)-cycloaddition deprotonation (2′+4)-cycloreversion constitutes a potentially useful method for the oxidative cleavage of olefinic double bonds with concomitant extension of the carbon chain at one of the double bond termini (indirect «carboxolytic» cleavage of double bonds; see schemes 1 and 3).