598-61-8Relevant academic research and scientific papers
Mechanisms of Methylenecyclobutane Hydrogenation over Supported Metal Catalysts Studied by Parahydrogen-Induced Polarization Technique
Salnikov, Oleg G.,Burueva, Dudari B.,Kovtunova, Larisa M.,Bukhtiyarov, Valerii I.,Kovtunov, Kirill V.,Koptyug, Igor V.
, (2022/03/15)
In this work the mechanism of methylenecyclobutane hydrogenation over titania-supported Rh, Pt and Pd catalysts was investigated using parahydrogen-induced polarization (PHIP) technique. It was found that methylenecyclobutane hydrogenation leads to formation of a mixture of reaction products including cyclic (1-methylcyclobutene, methylcyclobutane), linear (1-pentene, cis-2-pentene, trans-2-pentene, pentane) and branched (isoprene, 2-methyl-1-butene, 2-methyl-2-butene, isopentane) compounds. Generally, at lower temperatures (150–350 °C) the major reaction product was methylcyclobutane while higher temperature of 450 °C favors the formation of branched products isoprene, 2-methyl-1-butene and 2-methyl-2-butene. PHIP effects were detected for all reaction products except methylenecyclobutane isomers 1-methylcyclobutene and isoprene implying that the corresponding compounds can incorporate two atoms from the same parahydrogen molecule in a pairwise manner in the course of the reaction in particular positions. The mechanisms were proposed for the formation of these products based on PHIP results.
GC/MS SEPARATION AND IDENTIFICATION OF THE C5H10 ISOMERS. APPLICATION TO THE Hg 6(3P1) PHOTOSENSITIZED REACTIONS OF cis-2-PENTENE, 1-PENTENE AND trans-1,2-DIMETHYLCYCLOPROPANE
Mare, George R. De,Termonia, Marc
, p. 155 - 160 (2007/10/02)
The analysis (separation and identification) of eleven C5H10 isomers is performed using coupled GC/MS with a 70 m glass capillary column containing a 2.5 μm thick film of PS225 as stationary phase.Cryogenic CO2 cooling improves the separations.The total analysis time is less than 12 minutes. - Some mechanistic details on the Hg 6(3P1) (hereafter denoted by Hg*) photosensitization of the title compounds are elucidated.Thus the Hg* photosensitization of cis-2-pentene at 20 Torr yields methylcyclobutane with a quantum yield Φ = O.1, not ethylcyclpropane as was previously thought. (Ethylcyclopropane is formed in trace quantities.) The photostationary state for the Hg* sensitization of the 2-pentenes is confirmed to correspond to the concentration ratio / = 1.00.Trans-1,2-dimethylcyclopropane is a product of the Hg* photosensitization of 1-pentene.The major products of the Hg* photosensitization of trans-1,2-dimethylcyclopropane at 80 Torr are 3-methyl-1-butene, trans- and cis-2-pentene and cis-1,2-dimethylcyclopropane which are all formed with quantum yields near 0.1 and in the ratios 1.04 : 1.07 : 1.00 : 1.45.
Synthese von Cyclobutan durch Dehalogenierung von 1,4-Dihalogenbutanen mit Alkalimetalldaempfen. Zur Relation von radikalischen und metallorganischen Reaktionskanaelen
Volnina, S. A.,Avakjan, V. G.,Guselnikov, L. E.,Yaya, A. Al
, p. 1061 - 1072 (2007/10/02)
Gasphase dehalogenation of 1,4-dichloro-, 1-chloro-4-bromo-, 1,4-dibromobutanes and 1,4-dibromopentane by Na/K vapors produces cyclobutane resp. methylcyclobutane with selectivities of 55.5, 46.7, 32.0 and 17 moles/100 moles resp..Side products of the reaction are ethylene and hydrogen, yields of which increase with increasing temperature and rising degree of substitution of chlorine by bromine.A mechanism is discussed in which the initiation step is the generation of halobutyl radicals of the type H2C*-(CH2)2-CH2X (X = Cl, Br) which are reacting further in two ways - by formation of tetramethylenediradical, splitting off the second halogen atom, or by the formation of the metallorganic compound 1-potassium-4-halogenobutane, which further cyclisizes to cyclobutane splitting off KX.Using some methods of theoretical chemistry such as quantumchemical calculations based on ab initio (STO-3G) and semiempirical (AM1) structures, on the relative energies of conformers of halogenobutylradicals and on models of the metallorganic intermediates, but also by conformation calculations of the content of rotation isomers of the intermediate formed, the correlation between the two reaction channels depending on the type of halogen was estimated.The calculations showed that only about 20 percent of cyclobutane are generated by the radical pathway.The high predominance of the metallorganic channel in the case of 1,4-dichlorobutane is caused by the high lifetime of chlorobutyl radicals in comparison with its bromoanalogues.
The Kinetics and Mechanism of Ring Opening of Radicals containing the Cyclobutylcarbinyl System
Beckwith, Athelstan L. J.,Moad, Graeme
, p. 1083 - 1092 (2007/10/02)
The kinetic parameters of β-fission of radicals containing the cyclobutylcarbinyl system have been determined by analysis of the mixtures obtained when suitable chloro-compounds are treated with tributylstannane.Under these conditions ring opening is irreversible and in the rigid bicyclic system (4) is under stereoelectronic control.For ring opening of cyclobutylcarbinyl radical (8) kf = 4.3 x 103 s-1 at 60 deg C, and the best values of the activation parameters appear to be ΔH(excit.) = 12.2 kcal mol-1 and ΔS(excit.) = -7.4 cal mol-1 K-1.Monocyclic systems undergo preferential fission of the more substituted βγ-bond.Methyl substituents at the α-, β-, or δ-positions have little effect but γ-substitution strongly enhances the rate of ring opening.The transition state is reactant-like and has a similar disposition of centres to that (1) for homolytic addition.
