Nitration of p-anisic acid in clay microenvironment yields 2,4-dinitro
anisole in about 40-60% yield, in addition to the conventional nitrati
on product, namely 3-nitro-4-methoxybenzoic acid. While clay directed
nitration of p-methoxyacetophenone gives only 3-nitro-4-methoxy-acetop
henone, with m-nitrobenzoic acid, nitrodecarboxylation yielding m-dini
trobenzene is the only reaction course. The observed greater ipso-nitr
ation facilitated by a nitro group may be attributed to the greater ea
se with which the Wheland intermediate may decompose via a cyclic six-
membered transition state.