Croatica Chemica Acta, Vol. 49 No. 4, 1977.
Original scientific paper
n-Participation in Solvolysis and Secondary Deuterium Isotope Effects. Octahydrodimethanonaphthalene System
R. Malojčić
; Faculty of Pharmacy and Biochemistry University of Zagreb, 41000 Zagreb
S. Borčić
; Faculty of Pharmacy and Biochemistry University of Zagreb, 41000 Zagreb
D. E. Sunko
; Faculty of Pharmacy and Biochemistry University of Zagreb, 41000 Zagreb
Abstract
Specifically deuterated brosylates of unsaturated carbinols with
endo-, exo-fused norbornanes structure 4-0H were prepared and
their acetolysis rates measured at 25.0 °c. A secondary a-deuterium
isotope effect of kH/kn = 1.20 was obtained which is close to the
characteristic maximum for solvolysis of sulfonate esters. This result
is rationalized in terms of an exponential correlation between the
magnitude of the a-d effect and the bond order to incoming and
leaving groups. The conclusion is reached that even large rate
accelerations may indicate extensive charge delocalization occurring
at large internuclear distances between the neighboring group and
the reaction center in the transition state. Acetolysis of the compound
with deuterated double bond (4-0Bs-d6) proceeds with an
inverse isotope effect (kH/kn = 0.93) which is analogous to other
cases of n-participation.
Keywords
Hrčak ID:
196146
URI
Publication date:
26.4.1978.
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