Elimination Of Ethane Research Articles

ChemInform Abstract: Cycloaddition of Vinylindoles to Anellated Indole Derivatives. Part 7. New Regio‐ and Stereocontrolled Reactions of 2‐Vinylindoles with CC‐Dienophiles: Diels‐Alder Reactions, Ene Reactions, and Michael Additions.

Abstract2‐Vinylindole (I) reacts with methyl propiolate (II) to give the carbazole (III) via cycloaddition and subsequent elimination of ethylene.

Source of ethane in expirate of rats ventilated with 100% oxygen.

Ethane in alveolar expirate may have its source in organs other than the lung and be transported to the lung for elimination. We determined ethane production rates in rats (group I) ventilated with hydrocarbon-free air (HFA) before and after exsanguination. To determine whether the lung is the source of increased ethane production during exposure to 100% O2, we measured ethane in the expirate of nine exsanguinated, Sprague-Dawley rats (group II) mechanically ventilated with HFA and then with 100% O2. In all nine animals, ethane elimination rates on 100% O2 increased compared with HFA values. In five of the nine rats, HFA ventilation was reinstated after O2 (group III). In all five, ethane elimination fell with HFA ventilation compared with the value on 100%. Six rats with circulation intact were ventilated with HFA and then 100% O2 (group IV). Ethane production rate for group IV animals breathing HFA was not significantly different from the exsanguinated animals in group II while ventilated with HFA. The mean increase in ethane production for the group II animals was not significantly different from the group IV animals. Lung slices from four other rats (group V) were incubated in saline at 37 degrees C with FeCl2 (10 mg) added to enhance free radical formation. Paired lung samples from the same rat were incubated with either HFA or 100% O2. Headspace gas was analyzed chromatographically for ethane at 120 min. Mean ethane in the O2 samples was higher than for HFA. Rat lung tissue is the main source of increased ethane production during 100% O2 exposure.

Ethane production rates and minute ventilation

Ethane quantitated in the expired alveolar gas is a noninvasive measure of free radical activity. This method has been criticized for lack of control of minute ventilation (VE) in spontaneously breathing animals, although ethane, which is poorly soluble in tissues, should not be affected by changes in VE. We measured ethane elimination rates in six strain 13 guinea pigs (GP13) during spontaneous room air breathing and in six room air breathing, pentobarbital-anesthetized, tracheostomized, externally warmed, mechanically ventilated GP13s at various levels of VE. In the ventilated animals, weight0.75/VE (metabolic activity corrected for VE) was a linear function of arterial CO2 tension (PaCO2) drawn from arterial line (r = 0.72, P less than 0.005). However, weight0.75/VE did not correlate with ethane elimination rates (r = 0.12, not significant). The mean (+/- SD) ethane elimination rates in the spontaneously breathing animals was 3.15 +/- 0.96 pmol.min-1.100 g-1 and was not significantly different from the mean rate in the mechanically ventilated animals (3.11 +/- 1.37) over a range of VE's. These data demonstrate that ethane elimination rates are not affected by changes in VE and are unaffected by pentobarbital anesthesia.

Efficient gas phase polymer deposition by infrared laser-photosensitized decomposition of 4-silaspiro[3.4]octane

Laser-induced thermolysis of 4-silaspiro[3.4]octane is an efficient method for the gas phase deposition of organosilicon polymer, which is assumed to arise from 1-methylene-1-silacyclopentane generated upon the elimination of ethene from the parent molecule.

Fragmentation reactions of the enolate ions of 2‐pentanone

AbstractThe reaction of [OH]− with 2‐pentanone produces two enolate ions, [CH3CH2CH2COCH2]− and [CH3COCHCH2CH3]−, by proton abstraction from C(1) and C(3), respectively. Using deuterium isotopic labelling the fragmentation reactions of each enolate have been delineated for collisional activation at both high (8 keV) and low (5–100 eV) collisional energies. The primary enolate ion fragments mainly by elimination of ethene. Two mechanisms operate: elimination of C(4) and C(5) with hydrogen migration from C(5), and elimination of C(3) and C(4) with migration of the C(5) methyl group. Minor fragmentation of the primary enolate also occurs by elimination of propane and elimination of C2H5; the latter reaction involves specifically the terminal ethyl group. The secondary enolate ion fragments mainly by loss of H2 and by elimination of CH4; for the latter reaction four different pathways are operative. Minor elimination of ethene also is observed involving migration of a C(5) hydrogen to C(3) and elimination of C(4) and C(5) as ethene.

Carbon-carbon and carbon-hydrogen bond activation at ditungsten centers supported by alkoxide ligands

Abstract

Mechanism and energetics of reductive elimination of ethane from some tetramethylplatinum(IV) complexes

The new complexes cis-[PtMe4L2], L = MeNC or 2,6-Me2C6H3NC, decompose cleanly in the solid state or in solution to give ethane and cis-[PtMe2L2]. Studies using differential scanning calorimetry give a value of (PtMe)= 133 ± kJ mol–1for the mutually trans PtMe groups, and deuterium-labelling studies show that the reductive elimination step is intramolecular. Kinetic studies show that the reaction occures very largely after ligand dissociation and gives a value of k(PtCH3)/k(PtCD3)= 1.30 ± 0.04. It is suggested that an agostic interaction of one CH3Pt group in the five-co-ordinate intermediate precedes the reductive elimination step and reasons for this proposal are advanced.

Isolation of cis-dimethyl(methoxycarbonyl)(triphenylphosphine)gold(III)

Cis-Dimethyl(methoxycarbonyl)(triphenylphosphine)gold(III) (1) has been prepared by the reaction of carbon monoxide with a mixture of cis-dimethyliodo(triphenylphosphine)gold(III) and sodium methoxide in methanol. Thermolysis of 1 results in the competitive reductive elimination of methyl acetate and ethane

The translational energy distributions for metal atoms and ions produced via visible laser MPD/MPI of group 13 metal alkyls and MPI of aluminum and indium atomic beams

The nascent translational energy distributions of group 13 metal ions produced via multiphoton dissociation and multiphoton ionization (MPD/MPI) of their trimethyl derivatives and via multiphoton ionization of metal atomic beams have been measured using time-of-flight mass-spectroscopy. In all cases the ion production was isotropic and the translational energy distribution was approximately Boltzmann. For ionization of free aluminum and indium atoms translational temperatures of 6K and 4K were measured, corresponding to most probable velocities of 60 and 24 ms−1. From multiphoton dissociation of trimethylaluminum, trimethylgallium, and trimethylindium, translational temperatures of 1800, 700, and 900 K resulted. These correspond to velocities of ∼1000, 400, and 350 ms−1. A photodissociation mechanism involving elimination of ethane followed by dissociation of monomethyl metal intermediates to produce metal atoms is in reasonable agreement with the experimental data. The nascent velocities of metal atoms and ions from the metal alkyl and metal beam sources are used to assess the potential of these sources for microfabrication of metal structures.

A combined field ionization kinetics, collision-induced, and stable isotopic labelling study of the ethene and ethyl (and subsequent) eliminations from the molecular ion of 2-ethylbutanoic acid

It is shown by field ionization kinetics that the ethene elimination from ionized 2-ethyl-butanoic acid is the most dominant channel at molecular ion lifetimes ⩽10 −9 s. This channel, however, becomes rapidly less important with respect to ethyl elimination at molecular ion lifetimes ⪢10 −9 s. Both eliminations occur without any detectable exchange between hydrogen or carbon atoms from different positions as shown by specific 2H- and 13C-labelling. The same observations are made for molecular ions decomposing in the metastable time frame of 10 −6 to 10 −5 s. On the basis of collision-induced dissociation experiments, it is demonstrated that ∼95% of the (MC 2H 5) + ions have the structure of carbonyl oxygen-protonated crotonic acid which, in line with the 2H- and 13C-labelling, are formed by a successive, irreversible hydrogen shift from C-3 to the carbonyl oxygen and cleavage of the C-2C′-3 bond to eliminate ethyl. The remaining ∼5% of the (MC 2H 5) + ions have the structure of carbonyl oxygen-protonated methacryclic acid. In line with the 2H- and 13C-labelling results, these ions are generated by a successive, irreversible hydrogen shift from C-3 to the carbonyl oxygen, migration of the C(OH) 2 group from C-2 to C-3, a hydrogen shift from C-3 to C-2, and eventual cleavage of the C-2C′-3 bond to eliminate ethyl. Further metastable decompositions of the (MC 2H 5) + ions correspond to eliminations of molecules of water, C 2H 2O, and C 2H 4O. The water molecule contains the original hydroxylic hydrogen and one of the hydrogen atoms of C-3. The eliminated C 2H 2O molecule contains the C-1 and C-2 atoms, while the eliminated C 2H 4O molecule contains the C-3 and C-4 atoms. Combined with the obtained 2H-labelling results, strong support, if not evidence, is provided for the intermediacy of ion/molecule complexes during the eliminations of C 2H 2O and C 2H 4O from the (MC 2H 5) + ions.

Reactivity and mechanism in oxidative addition to palladium(II) and reductive elimination from palladium(IV) and an estimate of the palladium methyl bond energy

Oxidative addition of methyl iodide to [PdMe2(bpy)]( bpy = 2,2'-bipyridine) occurs by the SN2 mechanism. Evidence includes the observation of second-order kinetics in acetone solvent, with a large negative value for the entropy of activation, and the observation of a cationic species, [PdMe3(bpy)(CD3CN)]+ in, CD3CN solvent. The reaction occurs more slowly than the analogous reaction of [PtMe2(bpy)], but the same mechanism operates. Reductive elimination from [PdIMe3(bpy)] to give ethane and [PdIMe(bpy)] follows good first order kinetics, occurs more rapidly in polar solvents, and is strongly retarded by added iodide. These observations are interpreted in terms of a mechanism that involves preliminary ionization of iodide followed by reductive elimination from the cation [PdMe3(bpy)]+. Studies by differential scanning calorimetry allow an estimate of the Pd-C bond energy of -130 kJ mo1-l to be obtained, and this value is considerably higher than the activation energy for reductive elimination of ethane from [PdIMe3(bpy)]. The reductive elimination step is therefore concerted, and possible mechanisms, which may involve direct C-C coupling or C-C coupling after an agostic CHPd interaction, are discussed. This work is relevant to catalytic C-C coupling reactions using palladium complex catalysts

HOFMANN ELIMINATION REACTION WITH PHOSPHORUS CONTAINING ALKYLAMMONIUM SALTS

Abstract Ethylammonium phosphite salts, formed by alkyl transfer from dialkyl phosphites to tertiary amines, undergo a Hofmann elimination of ethylene.

IR laser photosensitized decomposition of 1-methyl-1-silacyclobutane. Efficient gas-phase polymer deposition

Laser-induced thermolysis of 1-methyl-1-silacyclobutane is a highly selective method for the gas-phase deposition of organosilicon polymer, which is formed by the elimination of ethene and the major participation of methylsilaethene and dimethylsilylene in the polymerization.

ChemInform Abstract: Kinetics and Mechanism of the Thermal Reactions of endo‐ and exo‐5‐Cyanobicyclo(2.2.2)oct‐2‐ene and Methyl‐Substituted Derivatives in the Gas Phase

The thermal reactions of endo- and exo-5-cyanobicyclo-[2.2.2]oct-2-ene and their trans- and cis-6-methyl-substituted derivatives have been investigated in the gas phase between 518 and 630 K. Each product decomposes by two parallel first-order retro-Diels-Alder reactions, a main one with formation of cyclohexa-1,3-diene and a minor one with elimination of ethene. Slight isomerizations are also observed. The kinetic results can be explained in terms of a biradical mechanism. The rate-determining step is shown to depend on the amount of resonance energy in the biradical. Heats of formation and entropies of the bicyclo[2.2.2]oct-2-enes studied are estimated.

Non-specific hydrogen abstractions in alkane eliminations from ionized ketones. Further evidence that alkane eliminations are ion-neutral complex-mediated

Ionized ketones are shown to eliminate alkanes by processes in addition to the previously characterized 1,2-eliminations of alkyl moieties and an opposite α-hydrogen. Ionized 2-methyl-3-pentanone interchanges α-hydrogen across the carbonyl group by hydrogen transfers interconverting isopropyl radical and propane-containing ion-neutral complexes. In contrast, in ionized 3-pentanone, β- as well as α-hydrogens are abstracted by ethyl, leading to some formation of CH α 2H βCH αCO + upon ethane elimination. This may be due to ion-assisted isomerization of the ethyl radical in the complex [CH 3CH 2CO +·CH 2CH 3] followed by reformation of the 3-pentanone ion prior to decomposition.

Studies on Organoaluminum Precursors OP Aluminum Nitride Fibers

ABSTRACTA melt-spinnable precursor of aluminum nitride fibers derived from triethylaluminum and ammonia contains AlNH, AlNH2 groups, and a small number of AlN units characteristic of aluminum nitride. The molecular weight of a spinnable composition is 070, corresponding to an average molecular weight of 13 organoaluminum groups. Ammonia, a curing agent for the fibers, accelerates elimination of ethane from the material, and decreases its solubility in toluene.

Kinetics and mechanism of the thermal reactions ofendo- andexo-5-cyanobicyclo[2.2.2]oct-2-ene and methyl-substituted derivatives in the gas phase

The thermal reactions of endo- and exo-5-cyanobicyclo-[2.2.2]oct-2-ene and their trans- and cis-6-methyl-substituted derivatives have been investigated in the gas phase between 518 and 630 K. Each product decomposes by two parallel first-order retro-Diels-Alder reactions, a main one with formation of cyclohexa-1,3-diene and a minor one with elimination of ethene. Slight isomerizations are also observed. The kinetic results can be explained in terms of a biradical mechanism. The rate-determining step is shown to depend on the amount of resonance energy in the biradical. Heats of formation and entropies of the bicyclo[2.2.2]oct-2-enes studied are estimated.

ChemInform Abstract: Potential Energy Profile of a Full Catalytic Cycle of Olefin Hydrogenation by the Wilkinson Catalyst.

It is only in the last few years that for elementary reactions of organotransition-metal compounds the transition-state geometry can be optimized and the potential energy profile can be obtained from ab initio molecular orbital calculations. Elementary reactions thus studied include oxidative addition/reductive elimination, olefin insertion/..beta..-elimination carbonyl insertion, thermolysis of ketene complexes, and isomerization of metallacycle to an alkylidene-olefin complex. Despite such success, a study of an entire cycle of a catalytic process, consisting of several elementary reactions, has been a challenge to theoreticians. The authors communicate here the results of the first such study, on homogeneous olefin hydrogenation by the Wilkinson catalyst. They concentrate on the dominant catalytic cycle of the mechanism proposed by Halpern. The model of the cycle they adopted, consists of oxidative addition of H/sub 2/, coordination of ethylene, ethylene insertion, isomerization, and reductive elimination of ethane.

ChemInform Abstract: Multiple Bonds Between Main‐Group Elements and Transition Metals. Part 40. Glycolate and Thioglycolate Complexes of Rhenium and Their Oxidative Elimination of Ethylene and of Glycol.

AbstractThe Criegee and the Sharpless variants of olefin oxidation on MnO4‐ and OsO4‐catalysts, resp., presumably proceed via glycolate complexes as intermediates.

Potential energy profile of a full catalytic cycle of olefin hydrogenation by the Wilkinson catalyst

It is only in the last few years that for elementary reactions of organotransition-metal compounds the transition-state geometry can be optimized and the potential energy profile can be obtained from ab initio molecular orbital calculations. Elementary reactions thus studied include oxidative addition/reductive elimination, olefin insertion/..beta..-elimination carbonyl insertion, thermolysis of ketene complexes, and isomerization of metallacycle to an alkylidene-olefin complex. Despite such success, a study of an entire cycle of a catalytic process, consisting of several elementary reactions, has been a challenge to theoreticians. The authors communicate here the results of the first such study, on homogeneous olefin hydrogenation by the Wilkinson catalyst. They concentrate on the dominant catalytic cycle of the mechanism proposed by Halpern. The model of the cycle they adopted, consists of oxidative addition of H/sub 2/, coordination of ethylene, ethylene insertion, isomerization, and reductive elimination of ethane.