Page 339 - Mechanism and Theory in Organic Chemistry

H3C CH3

inversion
N-H
I
H H
128

126
127
relative yields change drastically. Table 6.2 gives the data. (Bromine, a "heavy
atom," is known to catalyze singlet-triplet conversions-see Section 13.1, p. 687.)
Thus in bromoform-methanol the ratio (126 + 127)/128 is only 0.02. This
experiment indicates that a nitrenium ion must exist as a discrete intermediate-
with a long enough lifetime to undergo spin inversion.
Nitrenium ions can also be generated by solvolyzing esters of N,N-di-
alkylhydroxylamines. 3,5-Dinitrobenzoates (129) were found to be the most
useful hydroxylamine derivatives.171

Table 6.2 PRODUCTS FROM SOLVOLYSIS 125
OF
Percent yield
Solvents 126 + 127
126 127 128 128

SOURCE: G. Gassman, Accts. Chem. Res., 3, 26 (1970). Reprinted by permission of the American
P.
Chemical Society.

171 P. G. Gassman and G. D. Hartman J. Amr. Chem. Soc., 95, 449 (1973).