Gas phase basicity of X(CH2)3Y(X, Y = OH, NH2) by the thermokinetic method

Gas phase basicity of three homologuous bidentate bases: 1,3-propanediamine, 1, 1,3-propanolamine, 2, and 1,3-propanediol, 3, has been determined by Fourier transform ion cyclotron resonance mass spectrometry. Both, the equilibrium and the thermokinetic methods were used and the results were compared with previous experimental and theoretical determinations. An excellent agreement is generally found between the gas phase basicities given by all the methods if corrections due to entropy variations are taken into account. In particular it is shown that a correction given by the term ΔGa°=−(T−298)[〈ΔpS298°(Bi)〉−ΔpS298°(M)], where T is an “effective temperature” and ΔpS° the protonation entropy of the considered species, should be applied to the thermokinetic determination.