Carbon-13 kinetic isotope effects. IV. The effect of temperature on k12/k13 for benzyl halides in bimolecular reactions

1968 ◽  
Vol 46 (11) ◽  
pp. 1825-1829 ◽  
Author(s):  
Jan Bron ◽  
J. B. Stothers
Keyword(s):  
Temperature Dependence ◽  
Temperature Effect ◽  
Isotope Effects ◽  
Benzyl Bromide ◽  
Kinetic Isotope Effects ◽  
Effect Of Temperature ◽  
Large Temperature ◽  
Bimolecular Reactions ◽  
Kinetic Isotope ◽  
Benzyl Halides

The temperature dependence of the 13C kinetic isotope of the α-carbon in benzyl bromide (1) and in 1-bromo-1-phenylethane (2) has been measured for reaction with alkoxide ion. For these bimolecular displacements, a relatively large temperature effect was found, comparable to that reported for other SN2 processes. A reexamination of the reaction of 2 with EtO− has shown an earlier value for k12/k13 to be in error.

CARBON-13 KINETIC ISOTOPE EFFECTS IN BIMOLECULAR REACTIONS

1962 ◽  
Vol 40 (10) ◽  
pp. 2007-2011
Author(s):  
J. B. Stothers ◽  
A. N. Bourns
Keyword(s):  
Isotope Effects ◽  
Benzyl Bromide ◽  
Kinetic Isotope Effects ◽  
Bimolecular Reaction ◽  
Alcohol Solution ◽  
Ionic Character ◽  
Compound I ◽  
Bimolecular Reactions ◽  
Kinetic Isotope ◽  
Methoxide Ion

Carbon-13 kinetic isotope effects have been measured for the bimolecular reaction of 1-phenyl-1-bromoethane (I) and benzyl bromide (II) with alkoxide ion in alcohol solution. Compound I gave an effect, k12/k13, of 1.0032 ± 0.0005 for reaction with ethoxide ion in ethanol, while II gave k12/k13 = 1.0531 ± 0.0004 for reaction with methoxide ion in methanol. These surprisingly different effects are tentatively interpreted in terms of a model for the transition state having varying degrees of ionic character.

DEUTERIUM KINETIC ISOTOPE EFFECTS: V TEMPERATURE DEPENDENCE OF β-DEUTERIUM EFFECTS IN WATER SOLVOLYSIS OF ISOPROPYL COMPOUNDS

1961 ◽  
Vol 39 (10) ◽  
pp. 1989-1994 ◽  
Author(s):  
K. T. Leffek ◽  
R. E. Robertson ◽  
S. E. Sugamori
Keyword(s):  
Temperature Dependence ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Zero Point ◽  
Kinetic Isotope Effects ◽  
Methyl Groups ◽  
Deuterium Isotope Effect ◽  
Point Energy ◽  
Kinetic Isotope ◽  
Enthalpy Of Activation

The secondary β-deuterium isotope effect (kH/kD) has been measured over a range of temperature for the water solvolysis reactions of isopropyl methanesulphonate, p-toluenesulphonate, and bromide. In these cases the isotope effect is due to a difference in entropies of activation of the isotopic analogues rather than a difference in the enthalpies of activation. It is suggested that the observed isotope effect is due to internal rotational effects of the methyl groups in the isopropyl radical, and the lack of an isotope effect on the enthalpy of activation is accounted for by a cancellation of an effect from this source and one from zero-point energy.

Temperature Dependence and Deuterium Kinetic Isotope Effects in the CH (CD) + C2H4(C2D4) Reaction between 295 and 726 K

2001 ◽  
Vol 105 (22) ◽  
pp. 5393-5401 ◽  
Author(s):  
Holger Thiesemann ◽  
Eileen P. Clifford ◽  
Craig A. Taatjes ◽  
Stephen J. Klippenstein
Keyword(s):  
Temperature Dependence ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope
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