The identity carbon-to-carbon proton transfers between nitromethane and nitromethide anion and between oxygen protonated nitromethane and aci-nitromethane have been studied by ab initio methods. Group charges calculated by Mulliken and NPA methods as well as geometrical parameters such as pyramidal angles and C-N bond lengths indicate that the transition states of these reactions are strongly imbalanced. Further evidence for the imbalance comes from a consideration of the relative energies of the various corners representing hypothetical intermediates on More O’Ferrall-Jencks diagrams. Our results for the CH3NO2/CH2=NO2- system, in conjunction with previous findings on other CH3Y/CH2=Y- systems, indicate an increase in the imbalance in the order CN much less than CH=O less than or equal to CH=CH2 less than or equal to NO2 consistent with the notion that imbalances increase with pi-acceptor strength of Y. However, when comparing the CH3N+O2H/CH2=NO2H system with the CH3NO2/CH2=NO2- system, the results are somewhat ambiguous as to whether the stronger pi-acceptor (N+O2H) leads to a stronger imbalance. In contrast to numerous observations in solution reactions, there is no simple relationship between reaction barrier and imbalances in the gas phase, as becomes apparent when comparing our results with those for the systems CH3CH=O/CH2=CHO-, CH3CH=O+H/CH2=CHOH, CH3CN/CH2CN-, and CH3CH=CH2/CH2=CHCH2- reported in the literature. It is shown that the dependence of the barriers on the pi-acceptor is the result of a complex interplay among resonance/ imbalance effects, inductive/field effects, and electrostatic/hydrogen bonding effects.