In the gas phase, for the case of equation ( ), we can use the example of A being diethyl ether and M being CHCA to illustrate the tendency toward neutralization via proton transfer. The equilibrium constant is -613 kJ/mol or 10 32 when the pKa of 737 kJ/mol for protonated diethyl ether is used for AH + , pKa of 1350 kJ/mol of carboxylic acid is used for M, and the plume temperature is assumed to be 1,000 K. For the case of equation ( ), under the same assumptions for equation ( ) but with the counter anion being X -and with X -being hydrogen sulfate, the equilibrium constant is -457 kJ/mol or 10 . For the case of equation ( ), we can use the example of A being 15-crown-5 and Met + being Na + . The identity of X -is insignificant here. The equilibrium constant for the formation of A⁞Met + is 159 kJ/mol 51 or 10 8 favoring the A⁞Met + assuming the plume temperature is 1,000 K. In this case, neutralization via proton transfer in the gas phase cannot occur. Neutralization via ion pair formation to give A⁞Met + ⁞X -is similar as discussed earlier. At 2,200 K, the numbers become -606 kJ/mol or 10 14 for the case of equation ( ), and -445 kJ/mol or 10 10 for the case of equation (13).