- Alkene oligomerization process
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A process for oligomerising alkenes having from 3 to 6 carbon atoms which comprises contacting a feedstock comprising a) one or several alkenes having x carbon atoms, and, b) optionally, one or several alkenes having y carbon atoms, x and y being different, with a catalyst containing a zeolite of the MFS structure type, under conditions to obtain selectively oligomeric product containing predominant amounts of certain oligomers. The process is carried out at a temperature comprised between 125 and 175° C. when the feedstock contains only alkenes with 3 carbon atoms and between 140 and 240° C., preferably between 140 and 200° C. when the feedstock contains comprises at least one alkene with 4 or more carbon atoms.
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- Complexation of a Singlet Carbene by a Fluoroalkane. Modification of 1:CHCO2Et Selectivity in Perfluorohexane Solution and ab Initio Calculations
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We have compared product distribution from reactions of 1:CH2 with 2,5-dimethylhexane and 1:CHCO2Et with 2,3-dimethylbutane in alkane vs 1:1 pentane-perfluorohexane solution.A solvent effect was observed in the reaction of 1:CHCO2Et, but not 1:CH2.The preference for tertiary/primary C-H insertion by 1:CHCO2Et is 3.97 +/- 0.04 in 2,3-dimethylbutane solution and 4.48 +/- 0.09 in 1:1 pentane-perfluorohexane solution.There is no change in the stereospecificity of 1:CHCO2Et addition to cis-2-pentene in pentane vs 1:1 pentane-perfluorohexane solution, indicating that the observed change in selectivity is probably not due to intersystem crossing to 3:CHCO2Et.Ab initio calculations provide evidence for a possible origin of the solvent effect via formation of carbene-fluoroalkane complexes.At the RHF/3-21G level, 1:CHCO2Me forms bound complexes with CH3F and CF4 with binding energies ranging from 5.7-19.6 kcal/mol.These complexes are 1.3-1.7 times more strongly bound than complexes formed between 1:CH2 and the same fluoroalkanes.
- Swanson, Judith M.,Dvorak, Curt A.,DeLuca, JoAnn, P.,Standard, Jean M.
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p. 3026 - 3032
(2007/10/02)
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- A solvent effect in reactions of singlet methylene
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The effect of several solvents on the selectivity of singlet methylene (1:CH2) was investigated. It was found that product ratios from reactions in pentane, ethyl ether and cyclohexene solutions were identical; however, product ratios from reactions carried out in benzene were slightly different.
- Neugebauer,DeLuca
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p. 7169 - 7172
(2007/10/02)
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