1202-74-0Relevant academic research and scientific papers
Efficient and selective oxidation of methyl substituted cycloalkanes by heterogeneous methyltrioxorhenium-hydrogen peroxide systems
Bianchini, Gianluca,Crucianelli, Marcello,Canevali, Carmen,Crestini, Claudia,Morazzoni, Franca,Saladino, Raffaele
, p. 12326 - 12333 (2007/10/03)
Polymer-supported methyltrioxorhenium (MTO) systems are efficient catalysts for the oxidative functionalisation of cyclohexane and cyclopentane derivatives with H2O2 as oxygen donor. Using poly(4-vinyl)pyridine and poly(4-vinyl)pyridine-N-oxide as MTO supports, cycloalkanol, cycloalkanediol, cycloalkanone and ω-hydroxy methyl ketone derivatives were obtained in different yields depending on the experimental conditions. Interestingly, cycloalkane dimers were selectively recovered in acceptable to good yields when the oxidation was performed with polystyrene-microencapsulated MTO catalyst. The EPR investigation suggests that the homolytic cleavage of the CH3-Re bond with formation of CH3{radical dot} radicals occurs inside the polystyrene capsule, indicating a possible role of methyl radical in the cycloalkane dimerisation pathway.
Absolute rate constants for the addition of atomic hydrogen to monosubstituted and trisubstituted olefins
Tanner, Dennis D.,Zhang, Liying,Kandanarachchi, Pramod
, p. 11319 - 11324 (2007/10/03)
A mechanism is established for the formation of the products resulting from the solution phase regioselective addition of atomic hydrogen to 1-methylcyclohexene. From this data and new data for the reactions of 1-octene, the absolute rates and activation parameters for the addition of hydrogen atom to an olefin can be extracted. A method was established to determine the absolute rate of addition of a hydrogen atom to a terminal olefin in the solution phase. The addition rate constants, ka (25°C), to 1-octene [ka = (4.2 ± 3.6) × 109 M-1 s-1] and 1-methylcyclohexene [ka = (4.6 ± 0.8) × 106 M-1 s-1, -78°C] are found to be in reasonable agreement with the published values for the vapor phase rate of addition to ethylene. The large rate constants are supported by the observation that the activation parameters (Ea = 5.3 ± 2.9 kcal/mol and log A = 14 ± 3.5 M-1 s-1 for 1-octene) are consistent with the values expected for this fast reaction.
Formation of three-membered rings by SHi displacement. Reverse of cyclopropyl ring opening
Tanner, Dennis D.,Zhang, Liying,Hu, Li Qing,Kandanarachchi, Pramod
, p. 6818 - 6824 (2007/10/03)
The general methods, photoinitiated or peroxide-initiated free radical chain additions of halomethanes to olefins, yield 1,2-addition products at temperatures ranging from 20 to 100°C. At lower temperatures, -42 to -104°C, a competitive reaction, subsequent to the addition of CCl2X., yields alkylcyclopropanes. The reactions of 1-octene or 1-hexene and 1-methylcyclohexene with atomic hydrogen carried out in the presence of several transfer agents (CCl4, CCl3Br, CCl2Br2) initiate a radical chain addition of CCl2X. and yield cyclized materials resulting from the SHi displacement of halogen by a carbon-centered radical. The radical displacement of a halogen on carbon, the reverse of homolytic displacement on cyclopropyl carbon, is dominant at low temperatures. The rate constants for cyclization (kc) vs transfer with halomethane (kt) showed isokinetic temperatures of -46°C (CCl4, 1-hexene); -35°C (CCl4, 1-methylcyclohexene). The isokinetic temperatures for the reactions of the two substrates carried out in the presence of BrCCl3 were calculated as -204 °C (1-octene) and -109°C (1-methylcyclohexene).
