Kinetic isotope effect for the thermally-induced migration of hydrogen in cyclopentadienes

1969 ◽  
Vol 47 (9) ◽  
pp. 1555-1559 ◽  
Author(s):  
Stewart McLean ◽  
C. J. Webster ◽  
R. J. D. Rutherford
Keyword(s):  
Transition State ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Hydrogen Transfer ◽  
Arrhenius Parameters ◽  
Thermally Induced ◽  
Methyl Group ◽  
Hydrogen Migration ◽  
Kinetic Isotope ◽  
Non Linear

The Arrhenius parameters have been obtained for the rearrangement of 5-methylcyclopentadiene by a 1,2-hydrogen migration and for the corresponding rearrangement of 5-methylpentadeuteriocyclopentadiene. The results, taken in conjunction with those reported previously, allow the effect of the methyl group on the rate of hydrogen migration to be assessed. The kinetic isotope effect is of particular interest because the hydrogen transfer takes place through a transition state that is unequivocally non-linear.

Quantum Mechanical Tunneling in Homodienyl Sigmatropic [1,5]-Hydrogen Shifts of (Hydroxymethyl)styrylcyclopropanes

1990 ◽  
Vol 43 (6) ◽  
pp. 1071 ◽  
Author(s):  
GG Pegg ◽  
GV Meehan
Keyword(s):  
Low Temperature ◽  
Temperature Dependence ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Natural Compounds ◽  
Quantum Mechanical ◽  
Strong Temperature Dependence ◽  
Quantum Mechanical Tunneling ◽  
Hydrogen Migration ◽  
Kinetic Isotope

The strong temperature dependence of the deuterium kinetic isotope effect observed for homodienyl [1,5]-hydrogen migration of [hydroxy (D)methyl] styrylcyclopropanes (1c,d) in hexane solvent is suggestive of a significant tunnelling contribution to the mechanism. While the hydroxy substituent at the migration origin appears to influence the thermolytic behaviour of these molecules, attempts to promote oxy anionic homodienyl rearrangement in the isotopically natural compounds (1a,b) at low temperature were unsuccessful.

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