Abstract
Rate and equilibrium results for the reactions of 2-chloro-3,5-dinitropyridine and 2-ethoxy-3,5-dinitropyridine with a series of
p
-substituted anilines in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) were studied in DMSO. The reactions yielded 2-anilino-3,5-dinitropyridine derivatives, and no accumulation of intermediates could be detected spectrophotometrically. The rates were compatible with a two-step mechanism involving initial nucleophilic attack followed by either base-catalysed or uncatalysed conversion to the product. The base-catalysed pathway was likely to involve rate-limiting proton transfer from the zwitterionic intermediate to the base to yield the anionic
σ
-adduct. Plots of log
K
1
k
DABCO
against p
K
a
values gave good straight lines at 25 °C, with slopes of 0.42 for 2-chloro- and 0.45 for 2-ethoxy-3,5-dinitropyridine. The results were compared with those for the reactions of 2-phenoxy-3,5-dinitropyridine with substituted anilines.
Graphical abstract