Proton transfer reactions aryl nitroalkanes

Several papers dealing with computations of proton transfer reactions of nitroalkanes and aryl nitroalkanes have dealt with the energetics of the processes without finding any reaction intermediates and all resulted in support for the single-step mechanism. ... 

PROTON TRANSFER REACTIONS OF SIMPLE AND ARYL NITROALKANES IN SOLUTION AND IN THE GAS PHASE... 

The clearest example of the danger in using a as a measure of transition state structure is illustrated in the work of Bordwell et al. (1969, 1970, 1975). In the rate-equilibrium relationship for the deprotonation of a series of nitroalkanes the unprecedented Br nsted slopes of 1 61 for l-aryl-2-nitropropanes and 1-37 for 1-arylnitro-ethanes were obtained. The simple exposition of the mechanistic significance of a disallows values greater than 1. This, coupled with the fact that the transition state for the proton transfer is not product-like (as established by alternative criteria) indicates at best that, in at least some cases, a does not reflect the selectivity of a particular reaction. Several attempts to rationalize these anomalous results have been made. 

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