Synthesis of m-nitromethylbenzoate
Purpose:
To synthesize a disubstituted benzene ring by electrophilic aromatic substitution
Background:
The addition of a nitro group to a benzene ring is indicative of a type of reaction called
“electrophilic aromatic substitution”. When there is a group attached to the benzene ring in which the
atom directly attached to the ring bears positive character then the second group being added to the ring
will add in the meta position. In the nitration of methylbenzoate the carbon atom of the carbonyl bears
positive character. The first step of this mechanism is the generation of NO2+. This takes place by reacting
nitric acid HNO3 with sulfuric acid H2SO4 (Scheme 1). The addition step results from a pair of electron on
the benzene ring attacking the nitro group resulting in the formation of an allylic cation. Sulfate, which
was generated in the formation of the nitro group (Scheme 1), pulls off a proton from the benzene ring to
rearomatize the ring (Scheme 1).
HNO3+ 2H2SO4NO2
++ 2HSO4
-+ H3O+
CH
3
CO
O
NO2
+
CH
3
CO
O
NO
2
H
HSO4
-
CH
3
CO
O
NO
2
