Ionic assemblies of acetic acid and water form unlimited hydrogen bond networks. The stabilities of the networks correlate with the intrinsic acidities of the components, leading to strong CH3COO-âââHOOCCH3 bonds and weak CH3COO-âââH2O bonds. These relations apply from strong bonds in small aggregates to weak bonds in large assemblies, and affect the energies of acid dissociation and self-assembly. Partial solvation of CH3COO- by four H2O molecules facilitates acid dissociation and decreases the CH3COO--H+ bond dissociation energy by 332 kJ/mol (80 kcal/mol). The stabilites of the hydrogen bond networks increase with CH3COOH content, and aggregation decreases further the acid dissociation energy by forming strong CH3COO-âââHOOCCH3 bonds about the ions and by stabilizing the released protons in (CH3COOH)m(H2O)nH+ assemblies. The combination of strong CH3COO-âââHOOCCH3 bonds and weak CH3COO-âââH2O bonds makes self-assembly with solvent displacement particularly favorable for carboxylic acids, explaining their assembly in bilayers and membranes. Ab initio calculations show that isomeric assemblies with directly bonded and solvent-bridged structures have similar energies. As well, the solvent-bridged species CH3COO-âââH2OâââHOOCCH3 has similar energy to its cation-bridged isomer CH3COO-âââH3O+âââ-OOCCH3. In this transition state the adjacent anions stabilize the central cation, providing low-energy pathways for proton transfer between carboxylic groups.