Rapid Scan UV Spectroscopic and Kinetic Studies of the Reaction of Methyl 4-Methoxy-3,5-dinitrobenzoate with Pyrrolidine in Dimethyl Sulfoxide

Article abstract of DOI:10.1021/jo00205a018

An intermediate complex in the aromatic nucleophilic substitution reaction of methyl 4-methoxy-3,5-dinitrobenzoate with pyrrolidine in dimethyl sulfoxide has been observed by rapid scan UV spectroscopy, and kinetic and equilibrium constants have been obtained for its formation and decomposition.The observable intermediate is the conjugate base (I^-) of the zwitterionic form (IH).The formation of I^- is base catalyzed and the decomposition of I^- is first order in pyrrolidine hydrochloride.The possible mechanism is that proton transfer between IH and I^- is not more rapid than the k_-1 step and that general acid catalyzed leaving group departure from I^- is rate limiting.