We report the atmospheric pressure gas phase ion-molecule chemistry of the N2O2H- (m/z = 61) anion which is formed when certain hydrogen atom containing molecules are added to an N2O/Ar mixture in an atmospheric pressure ionization mass spectrometer (Ni-63-APIMS) source at pressures of similar to 1 atm and temperatures ranging from 373 to 600 K. By using the bracketing method, the gas phase acidity of N2O2H2 is found to be about the same as that of m-nitrotoluene Delta H-acid(g(degrees)) less than or equal to 365 kcal/mol. The rate constant for proton abstraction from nitromethane is comparable to other proton transfer reactions, k(t) = (2 +/- 0.4) x 10(-10) cm(3) molecule(-1) s(-1). N2O2H- reacts with aliphatic alcohols to form esters rather than by proton abstraction. The rate constant for esterification is 10-100 times lower than the rate constant for proton abstraction from nitromethane. SCF-MO calculations show that there are at least six local minima in the potential energy surface involving N2O2-. The structure with two oxygens bound to one nitrogen with a C-2 nu geometry, NNO2, corresponds to the global minimum. It is the only form with a calculated vertical electron affinity which is greater than 3.49 eV and will not undergo photodetachment at that energy as has been observed experimentally. Similar results are obtained for N2O2H-. The calculated heat of formation of the C-2 nu form of N2O2H- is -37.32 kcal/mol.