42843-17-4Relevant academic research and scientific papers
Differences in Mechanism and Rate of Zeolite-Catalyzed Cyclohexanol Dehydration in Apolar and Aqueous Phase
Chen, Feng,Shetty, Manish,Wang, Meng,Shi, Hui,Liu, Yuanshuai,Camaioni, Donald M.,Gutiérrez, Oliver Y.,Lercher, Johannes A.
, p. 2879 - 2888 (2021/03/09)
The rate of acid-base-catalyzed dehydration of alcohols strongly depends on the solvent and the environment of the acid sites. We find that Br?nsted acidic sites in large-pore zeolites, but not in medium-pore zeolites, catalyze cyclohexanol dehydration in decalin at significantly higher rates than hydrated hydronium ions in aqueous phase. Specifically, the difference in turnover rates between the two solvents amounts to 2-3 orders of magnitude on H-BEA and H-FAU, while being very modest (within a factor of 2) for H-MFI. Combining kinetic, isotopic tracer, and 2H NMR measurements, it is established that cyclohexanol dehydration generally follows an E1-elimination pathway in decalin. A notable exception is the monomer dehydration route on H-MFI, which exhibits a much lower activation energy and a substantially negative activation entropy that appear to be associated with an E2-type mechanism. The C-O bond cleavage displays a dominant degree of rate control in decalin, which stands in contrast to deprotonation (C-H cleavage) being rate-limiting in aqueous-phase dehydration.
Rhodium(II)-Catalyzed CH Insertions with imino>phenyl-λ3-iodane
Naegeli, Ivo,Baud, Corine,Bernardinelli, Gerald,Jacquier, Yvan,Moran, Mary,Mueller, Paul
, p. 1087 - 1105 (2007/10/03)
The catalyzed decomposition of imino>phenyl-λ3-iodane (NsN=IPh) resulted in formal insertions into CH bonds, activated by phenyl or vinyl groups, or by O-substituents.Scope and limitations of the reaction were investigated.Yields of up to 84percent were achieved in the most favorable cases.Yields were enhanced by electron-releasing substituents and decreased by steric hindrance.Aziridination competed with allylic insertion with olefinic substrates.The insertion reaction proceeded with retention of configuration.With chiral RhII catalysts, a modest asymmetric induction was observed.A mechanism involving direct insertion by a Rh-complexed nitrene into the CH bond is proposed.
Low-Temperature Hydrogenation of Cyclohexene by Energetic Forms of Hydrogen on the Ni(100) Surface
Son, Kyung-Ah,Mavrikakis, Manos,Gland, John L.
, p. 6270 - 6272 (2007/10/02)
Adsorbed cyclohexene can be hydrogenated at cryogenic temperatures by both incident gas phase atomic hydrogen and desorbing bulk hydrogen in the presence of adsorbed surface hydrogen on a Ni(100) surface.In both cases, no C-C bond activation is observed, and cyclohexane is the only hydrogenated product.Cyclohexene desorbs without significant reaction from the Ni(100) surface in the presence of coadsorbed surface hydrogen.Selective hydrogenation of adsorbed cyclohexene by bulk hydrogen is observed at 178 K in the leading edge of the bulk hydrogen desorption peak.Hydrogenation of adsorbed cyclohexene by gas phase atomic hydrogen is observed below 140 K.Isotope studies of the hydrogenation mechanism suggest that the hydrogenation of adsorbed cyclohexene by gas phase atomic hydrogen is a sequential process with the first hydrogen adding from the gas phase and the second from the surface.The small amount of benzene observed from adsorbed cyclohexene monolayers indicates that gas phase atomic hydrogen also causes some hydrogen abstraction.
γ-Silicon Stabilization of Carbonium Ions in Solvolysis. 4. Solvolysis of cis- and trans-3-(Trimethylsilyl)cyclohexyl and -3-tert-Butylcyclohexyl p-Bromobenzenesulfonates
Shiner, V.J.,Ensinger, Mark W.,Kriz, George S.,Halley, Karen A.
, p. 653 - 661 (2007/10/02)
The solvolyses of cis- and trans-3-(trimethylsilyl)cyclohexyl and -3-tert-butylcyclohexyl p-bromobenzenesulfonates (1-4) have been examined in several ethanol- and trifluoroethanol-water solvent mixtures.The α- and β-deuterium kinetic isotope effects have
Photochemistry of Alkyl Halides. 11. Competing Reaction via Carbene and Carbocationic Intermediates
Kropp, Paul J.,Sawyer, Joy A.,Snyder, John J.
, p. 1583 - 1589 (2007/10/02)
Isotopic analysis of the unsaturated products 6 and 15 resulting from irradiation of the labeled iodides 1-1,1-d2, 1-2,2-d2, and 13-1-d has revealed that they are formed substantially, but not exclusively, via α elimination.The unsaturated products thus arise via competing pathways involving carbene intermediates as well as the previously recognized radical and carbocationic intermediates.Irradiation of iodide 22 in methanol-d afforded ether 23 with partial incorporation of deuterium, but the accompanying ether 24 was formed with no detectable incorporation.Thus, ether 23 is formed via competing pathways involving the carbene 28 and the carbocation 25, whereas ether 24 is formed exclusively via the carbocationic pathway.A mechanism involving formation of the carbene intermediates via either α-hydrogen atom or α-proton transfer within the previously proposed intervening radical and ion pairs is suggested.One iodide studied, 17-2-d, exhibited no detectable α elimination.
