- Coordinated olefins as incipient carbocations: Catalytic codimerization of ethylene and internal olefins by a dicationic Pt(II)-ethylene complex
-
The coordinated ethylene molecule in the dicationic complex [(PNP)Pt(CH2=CH2)](BF4)2 (PNP = 2,6-bis(diphenylphosphinomethyl)pyridine) undergoes nucleophilic attack by free internal alkenes, giving the isolable c
- Hahn, Christine,Cucciolito, Maria E.,Vitagliano, Aldo
-
-
Read Online
- Thermal Reaction of Azoisopropane in the Presence of (E)-CH3CH=CHCH3: Reactions of the Radical 2-C3H7(.)
-
The azoisopropane-initiated thermal reaction of (E)-CH3CH=CHCH3 has been studied in the temperature range 489.5-542.0 K.For the reactions (CH3)2CHN=NCH(CH3)2 --> 2 2-C3H7(.) + N2 (1) 2-C3H7(.) + (E)-CH3CH=CHCH3 --> C3H8 + (E)-C4H7(.) (4) --> (CH3)2CHCH(CH3)CH(CH3)(.) (5) 2 2-C3H7(.) --> (CH3)2CHCH(CH3)2 (2) the following Arrhenius parameters were determined: log(k1/s-1) = (16.42 +/- 0.30) - (201.9 +/- 3.0) kJ mol-1/θ log4/k21/2)/dm3/2 mol-1/2 s-1/2> = (3.64 +/- 0.40) - (46.9 +/- 2.1) kJ mol-1/θ log5/k21/2)/dm3/2 mol-1/2 s-1/2> = (2.53 +/- 0.60) - (39.5 +/- 2.4) kJ mol-1/θ where θ = RT in 10.For the croos-combination ratios of the radicals 2-C3H7(.) and (Z)-C4H7(.), Φt = 2.12 +/- 0.10 was obtained, where the subscript t refers to the terminal combination.Formation of certain characteristic products was observed in various addition/isomerization/dissociation processes. 2-C3H7(.) addition to (E)-CH3CH=CHCH3 is suggested as the rate-determining step, followed by 1,4- and 1,5-H-atom shifts.
- Seres, Laszlo,Fischer, Ronald,Scherzer, Klaus,Goergenyl, Miklos
-
p. 1303 - 1312
(2007/10/02)
-
- CYCLIZATION OF C7-ALKANES OVER Pt BLACK CATALYST
-
C6-and C5-cyclization of heptane isomers (and also, olefin formation as a related process) over Pt-black have been studied in pulse and circulation systems.Hydrogendeficient conditions favour aromatization, via presumably terminal olefins.C5-Cyclization in the presence of more hydrogen is accompanied by internal olefin formation.Relative reactivities of all heptane isomers have been measured; this shows that cyclization is easier between terminal methyl groups.Optimum hydrogen pressures for both types of cyclization have been determined (and compared with hydrogenolysis, too).Earlier mechanism suggestion for aromatization and cyclopentane formation have been confirmed; the distinction between two types of bond shift mechanisms producing aromatics (from substituted pentanes) and saturated isomers, respectively, has recieved additional support facilitating the identification of these two reactions with mechanisms proposed in the literature.
- Zimmer, H.,Paal, Z.,Tetenyi, P.
-
p. 513 - 532
(2007/10/02)
-