Showing papers on "Cyclohexene published in 1970"

Nuclear Magnetic Resonance Spectroscopy. Carbon-13 Spectra of the Silver(l) Complexes of Cyclopentene and Cyclohexene

Abstract: In recent years, proton magnetic resonance spectroscopy has been utilized to investigate the nature of the species arising when alkenes are dissolved in solutions containing either silver(I) or mercury(II) ions. We report here on the use of high-resolution nmr spectra of ^(13)C (cmr) in natural abundance in examining such complexes.

Tracer studies of acid-catalyzed reactions. Part 10.—Deuterium exchange and isomerization of cyclic olefins over alumina

Abstract: The mechanisms of double-bond migration and the exchange of D2 with the hydrogen atoms of small cyclic olefins (methylenecyclobutane, methylenecyclopentane, cyclopentene, 3-methylcyclopentene, cyclohexene, and bicyclo-(2,2,1)-hepta-2, 5-diene) were investigated over a pure alumina catalyst. At temperatures below 100°, only those hydrogen atoms which were initially vinyl, or which could become vinyl by isomerization of the olefin, underwent exchange. A primary kinetic isotope effect of about 2.8 was found, indicating that cleavage of the C—H bond was probably the slow step in the exchange reaction. Rapid intermolecular scrambling of all vinyl hydrogen atoms was observed, and the presence of the olefins greatly reduced the usually fast rate of H2+ D2 equilibration. Double-bond migration below 100° was sensitive to the geometry of the olefin. Only molecules having a three carbon chain, including the double bond, which could appear concave when viewed from outside the molecule underwent isomerization; those which did not fulfill this requirement did not isomerize. Nearly pure 1,2-cyclopentene-d2 could be prepared, suggesting a dissociative mechanism for the exchange reaction. Hence, exchange and double-bond migration are independent processes, although both reactions may have involved the same sites and may have had a common intermediate. Poisoning experiments using radioactive CO2 indicated an active site density of about 1.4 × 1013 cm–2 for the exchange reaction after 530° pretreatment.

Dimer acid structures: Cyclic structures of clay catalyzed dimers of normal linoleic acid, 9-cis, 12-cis-Octadecadienoic acid

Abstract: The clay catalyzed dimer of linoleic acid has been examined by mass spectrometry of the unhydrogenated, the partially hydrogenated and completely hydrogenated dimer The results show that monocyclic, bicyclic and tricyclic structures are present Monocyclic structures predominate, bicyclic structures are also prominent, and tricyclic structures are relatively minor The monocyclic structure is believed to arise from a Diels-Alder type addition reaction The bicyclic structure may result from a free radical coupling followed by intramolecular ring closure The monocyclic structure in the unhydrogenated dimer appears to be mostly a benzene ring with saturated and unsaturated side-chains It probably is formed by hydrogen transfer from the Diels-Alder cyclohexene structure first formed Little, if any, of the Diels-Alder dimer structure as such is present The catalytic linoleate dimer has a higher ratio of monocyclic to bicyclic dimer than does the noncatalytic (thermal) dimer made from normal (nonconjugated) linoleate, while the thermal dimer of a conjugatedtrans-trans linoleate is exclusively monocyclic It is suggested that the clay catalyzes conjugation and hence favors the Diels-Alder reaction, and then catalyzes hydrogen transfer to aromatize the cyclohexene ring

New synthesis of (±)-cyclohexene-1,3/2,4-tetrol (conduritol-B)

Abstract: 1,4,5,6-Tetra-O-acetyl-myoinositol is reacted with N,N′-thiocarbonyl diimidazole to give 1,4,5,6-tetra-O-acetyl-myoinositol-2,3-thionocarbonate. This is desulfurized with trimethyl phosphite to yie...

Hydrogen–deuterium exchange of medium ring cycloalkenes during deuterogenation with tris(triphenylphosphine)chlororhodium(I)

Abstract: Cyclooctene, and, to a lesser extent, cycloheptene and cyclododecene undergo H–D scrambling during deuterogenation with tris(triphenylphosphine)chlororhodium(I), whereas this catalyst affords clean addition of two deuterium atoms to cyclohexene and 1-octene. Cyclooctene containing up to 0.4 deuterium atoms per molecule has been isolated after 50% reduction and the isotope shown to be randomly distributed about the ring. This unexpected exchange reaction has been accounted for in terms of the medium size ring effect (I-strain) and provides impressive further evidence for the reversible formation of a normally unobserved rhodium–alkyl species as an intermediate in the hydrogenation reaction.

Low‐Energy Electron‐Reflection Spectrometry for Thin Films of Aromatic and Aliphatic Molecules at 77°K

Abstract: Low‐energy electron‐reflection (LEER) spectra have been measured for thin films of pyridine, mesitylene, toluene, aniline, 1‐hexene, cyclohexene, 2‐methylpentane, and cyclohexane at 77°K. Differential plots show clearly defined peaks which appear to correspond to near‐resonant energy losses. For the aromatic molecules these peaks are matched by spectroscopically measured electronic energy levels, including both singlets and triplets. The aliphatic molecules show low‐lying bands in the LEER spectra, indicating states which have not been proposed previously and do not correlate with spectroscopically measured energy levels. For 1‐hexene the two lowest peaks occur at ∼ 3.1 and ∼ 4.6 eV; for cyclohexene at 3.0 and 4.7 eV; for 2‐methylpentane at 3.9 and 4.9 eV; and for cyclohexane at 3.9 and 4.8 eV.

Reaction of Olefin-Palladium(II) Chloride Complexes with n-Butylamine

Abstract: Olefin-palladium(II) chloride complexes reacted with n-butylamine to form Schiff’s bases. N-Ethylidene-n-butylamine was obtained by the reaction of the ethylene complex with n-butylamine, accompanied by reduction of palladium(II) to the metal. A tris(n-butylamine)palladium chloride complex was formed simultaneously by ligand substitution reaction. The yield of N-ethylidene n-butylamine was 15–19mol% (calcd on palladium) in 2.5 hr at 25°C, and decreased at temperatures higher than 60 °C with increasing reduction of palladium(II), owing to conversion of N-ethylidene-n-butylamine into either N-crotylidene-n-butylamine or a tarry polymeric substance by aldol type condensation reaction. The n-butylamine-palladium(II) chloride complex did not react with ethylene at 25°C, but reacted with ethylene at 150°C to form a large amount of tarry polymer and a small amounts of N-ethylidene-n-butylamine and N-crotylidene-n-butylamine. The propylene complex and the cyclohexene complex reacted with n-butylamine to yield bot...

Irradiation of Cyclohexene with 8.4, 10.0, and 11.6–11.8‐eV Photons. Dissociation of Neutral Excited Cyclohexene and Reactions of C6H10+

Abstract: The photolysis of cyclohexene has been investigated at photon energies above (10.0, 10.6–11.8 eV) and below (8.4 eV) its ionization potential (8.9 eV). The ionic processes were studied in a mass spectrometer equipped with a photon source. The parent C6H10+ ion was seen to undergo the following reactions with cyclohexene: C6H10++cyclo‐C6H10→cyclo‐C6H12+C6H8+, k = 0.7 × 10−10cm3/molecule·sec →C12H20+, k = 4.1 × 10−10cm3/molecule·sec. Analysis of the yields of cyclohexane formed in the first of these reactions in the photolysis at 10.0 eV over the pressure range 1–10 torr indicates that in this pressure range the relative importance of the two reactions is the same as in the ion source of the mass spectrometer at a pressure of 10−2 torr. At 11.6–11.8 eV the parent ion also dissociates, mainly to form C5H7+ and CH3. Evidence is presented which indicates that at these energies, the majority of the C6H10+ ions retain a cyclic structure. The neutral, electronically excited cyclohexene molecule dissociates mainly...

Photochemical reaction between acetone and cyclohexene in the liquid phase at 313 nm

Abstract: Seven products (table 1) were isolated from the reaction at 313 nm of which only four have been reported previously. The quantum yields of formation were measured and the variation of yield with concentration and temperature studied. Addition of samarium chloride and piperylene quenched the formation of some products. From their behaviour the products fall into three groups : (a) the addition compounds, (b) dicyclohexene and (c) isopropanol. Isopropanol and part of the dicyclohexene are formed as a result of hydrogen abstraction by triplet acetone from cyclohexene. The addition products are formed by rearrangement of an intermediate complex of triplet acetone and cyclohexene rather than by free radical reactions as suggested previously. The results are partly confirmed by some qualitative studies of the interaction of thermally produced radicals. The quantum efficiency for the formation of triplet acetone is approximately one. Ratios of the rate constants for reaction to deactivation of the triplet state have been determined.

Proton magnetic resonance studies of specifically deuterated cyclohexane compounds. Part I.: Cyclohexane and Methylcyclohexane

Abstract: The preparation of a specifically deuterated cyclohexane and some methyl-cyclohexanes by selective cis-addition of hydrogen to perdeuterated cyclohexene and 1-, 3-, and 4-methylcyclohexene is reported. The deuterium decoupled proton magnetic resonance spectra of these compounds are analyzed. The magnitude of the deuterium isotope effect is determined. The coupling constants show that no ring distortion is caused by the equatorial methyl group. There is an anomalous shift to higher field of the axial ring protons vicinal to the equatorial methyl group. This explains the absorptions at exceptionally high field observed for some di- and tri-methylcyclohexanes.

Photoreaction of Acetoacetate

Abstract: Methyl acetoacetate was irradiated in the presence of cyclohexene to afford methyl 3-cyclohexyl-3-hydroxybutyrate (VIII), methyl 3-cyclohexenyl-3-hydroxybutyrate (IX), two oxetanes (Xa and Xb), and cyclohexene dimers. In contrast to acetylacetone, acetoacetate behaves as a saturated ketone rather than as an α,β-unsaturated ester on photoreaction. We concluded that the n-π* excitation of the enol-form of β-dicarbonyl compound is responsible for photo-cycloaddition, and no effective n–π* excitation is accesisble on irradiaron of the enol-form of acetoacetate, since the enol form of acetoacetate has its n–π* and π-π* absorptions in the same region.

Stereoselektivität diastereogener CC‐Verknüpfungen, I. Die Beeinflußbarkeit der syn‐Stereoselektivität bei Carben‐Additionen an Olefine

Abstract: The syn-anti ratio of 7-(R-substituted)-norcaranes (I, R = Ph F, Cl) formed in the cycloaddn of cyclohexene (II) with PhCH2F, PhCH2Cl, PhCHBrF, PhCHBr2, FCHBr2, ClCHBr2, or CH2Cl and BuLi in various solvents under N was examd with respect to influences on the stereoselectivity II concn was the strongest factor while the nature of org halide, solvent, and Li halide formed influenced the selectivity also: syn-anti ratios 20-400 were obtained for (R = Ph) and 185-246 for I (R = halogen) I (R = Ph) rearranged to 2-benzyl-1-cyclohexene [on SciFinder (R)]

Acid-Catalyzed Oxidation of Olefins with Selenium Dioxide

Abstract: A drastic deviation from the usually accepted reaction path was observed when oxidation of olefins was carried out in acetic acid with selenium dioxide in the presence of concentrated sulfuric acid. Oxidation of cyclohexene gave a mixture of cis- and trans-1,2-diacetoxycyclohexane. It was shown that in the oxidation of cyclohexene the organoselenium intermediate which produced 3-acetoxy-1-cyclohexene on pyrolysis, is not the intermediate in the present reaction. A study on reaction variables, such as effect of molar ratio of cyclohexene to selenium dioxide, amount of sulfuric acid, and water, reaction time and temperature, was undertaken. The reaction was extended to 1-octene and 1-hexene. A general structure for the organoselenium compound produced in the oxidation of terminal olefins in acetic acid without sulfuric acid, has been proposed. On the basis of our data and some previous concepts a reaction scheme has also been given.

Reactions of Some Olefins with N-Chlorourea in the Presence of Acetonitrile

Abstract: A new three-component reaction of N-chlorourea, olefins and acetonitrile is reported. Styrene gives N-(1-ureidoethylidene)-2-choro-1-phenylethylamine, N-(2-chloro-1-phenylethyl)acetamide and 4-phenyl-2-oxazolidone. Addition proceeds in a Markovnikov manner as shown by structural evidence. Cyclohexene gives N-(1-ureiodoethylidene)-2-chlorocyclohexylamine and N-(2-chlorocyclohexyl)acetamide. The stereochemistry of the reaction has been shown to be trans as demonstrated by chemical and physical evidence. Mechanisms for the reaction are proposed.

Liquid Phase Chlorination of Olefins with Cupric Chloride. II. Stereochemistry of the Reactions of 2-Butenes and Cyclohexene

Abstract: Chlorination of cis-and trans-2-butenes with cupric chloride yields a mixture of meso- and dl-2,3-dichlorobutanes with meso/dl ratio of about 60/40, which is almost independent of the starting olefin configuration For cyclohexene, trans-1,2-dichlorocyclohexane is accompanied with the cis-dichloride, the amount of which depends upon the solvent polarities In all cases the starting olefins and the product dichlorides are sufficiently stable under the reaction conditions The results indicate that open ionic intermediates are involved in the chlorination of simple olefins in liquid phase reaction

Pentamethylcyclopentadienyl-rhodium and -iridium halides. Part III. Reactions with cyclohexadienes

Abstract: The dimeric dichloropentamethylcyclopentadienyl-rhodium and -iridium complexes (I) react with both cyclohexa-1,3- and 1,4-diene to give the π-cyclohexa- 1,3-diene-(pentamethylcyclopentadienyl)-rhodium and -iridium complexes. (IV). During this reaction, isomerisation of the uncomplexed cyclohexa-1,4- to the -1,3-diene occurred. The rhodium complex (IV) was a catalyst for the disproportionation of cyclohexa-1,3-diene to cyclohexene and benzene. This reaction was strongly assisted by the presence of the ethanol and base. Mechanisms for the complex formation, isomerisation, and disproportionation are suggested.