Cluster structures determined by ion-molecular interactions: preferential solvation and acid-base neutralization

The neutralization of CH3COOH by NaOH in water has been studied by the mass spectrometric analysis of clusters generated via fragmentation of liquid droplets. In water, CH3COOH molecules form self-association clusters at higher acid concentrations like the molar ratio of CH3COOH:H2O=1:10. At these concentrations, the neutralization takes place via interaction between the CH3COOH clusters and NaOH to afford Na+(CH3COOH)a(CH3COONa)b clusters. Furthermore, Na+ is preferentially solvated by CH3COOH in water to form Na+(CH3COOH)α clusters. In consideration with these cluster structure, the reaction mechanism in solution can be realized more precisely.