Addition to Carbon-Carbon Double Bonds
atoms in the resultant glycol becoming labelled, i.e. both are derived
from the permanganate and neither from the solvent.
O
II
If alkenes are oxidised by peracids, R—C—O—OH, the result is
an alkylene oxide or epoxide (XXV):
\y o \y ov
c «+X_X c\ \
II—»o c—R ;o c-
c*H c/ |
/\ H *0 /\. H-O
(XXV)It is possible, however, that in polar solvents the reaction may be
initiated by addition of ®OH obtained by breakdown of the peracid.
The epoxides may be isolated (cf. p. 70) and then undergo acid or
base-catalysed hydrolysis (a nucleophilic reaction) to yield the
1,2-diol. As attack must be 'from the back* on the cyclic epoxide,
inversion of configuration will take place at the carbon atom attacked
so that the ovfn^gmddition reaction to yield the 1,2-diol will be
tr
R R'
HO©—
N
o/ \
R R'R R'
\ /
HAO—>C
\e
OHAttack on only one carbon atom has'been shown above, but
equally easy attack on the other will lead to the mirror image of