Most organic reactions occur in solution, and particularly in the case of ions, one must consider non-bonded interactions with neighboring molecules. Non-bonded interactions, including hydrogen-bonding, also determine such physical properties as boiling point. For the most part these interactions may be understood in terms of electrostatics and polarizability. Artificial or natural ion carriers (ionophores) can be tailored to bind specific ions. Energetically the ionic dissociation of water in the gas phase is prohibitively expensive.