Page 307 - Mechanism and Theory in Organic Chemistry

results are shown in Equation 6.32, in which the numbers at the carbons of'the
products refer to the percent 14C found at that position in that product.76

A set of rapidly equilibrating carbenium iocs might account for the rearrange-
ments and the label scrambling; but this cannot be the correct explanation, for
cyclopropylcarbinyl, cyclobutyl, and allylcarbinyl systems all solvolyze much
more rapidly than would be expected from model compounds. Thus, for example,
the rate of solvolysis of cyclopropylcarbiny1 tosylate is lo6 times that of the solvent-
assisted solvolysis of isobutyl t~sylate.~~ Cyclobutyl tosylate solvolyzes 1 1 times

Relative rate: 1 O8 1
And
more rapidly than cyclohexyl to~ylate.~~ allylcarbinyl tosylate in 98 percent

Relative rate: 11 1
HCOOH solvolyzes 3.7 times faster than its saturated analog, in spite of the
electron-withdrawing effect of the double bond.79
-0~s -0~s
Relative rate: 3.7 1
Roberts suggested that a set of charge-delocalized, rapidly egilkatmg
carbon&m ions, wh~ch he caiied bicyc~~~orn, ----- first-formed -
--
ions
from
are
the
--
.
.
anthree ~ ~ ~ ~ m ~ ~ ~ ~ ~ & h t ~
the hamination - -.-. 14C-labeled - cyclopropylcarbinyl amine (Eggion 6.32).
of
--- -- A --
According to Roberts, _th_ere-w_&XTe two equivalent first-formed carbaniurn
ions: - A three-center bond could be formed from the develo- e
op C1 andZh-eT%;Gtals on C, and C, (path a) or orbiislion C, a s
---_
b). Once these carbonium ions were farmed, they ~o~ldb~mverte&te-ei+y
of
3*
the~~hsSSinnScheme Equilibration arrows should be shown
between all the structures, but their inclusion would further confuse this already
conceptually difficult scheme. Figure 6.8 shows an orbital representation of
bicyclobutonium ion (64).
78 See note 74, p. 293.
77 D. D. Roberts, J. Org. Chem., 29, 294 (1964); 30, 23 (1965).
H. C. Brown and G. Ham, J. Amer. Chem. Soc., 78, 2735 (1956).
79 See note 75, p. 293.