Thermolysis of NH4HCO3—A Simple Route to the Formation of Free Carbonic Acid (H2CO3) in the Gas Phase

“Carbonic acid cannot exist in the free state. ” Now, a surprisingly simple experiment has shown that this statement is wrong. Thermolysis of NH 4 HCO 3 affords, among other products, H 2 CO 3 , which is stable as both the neutral molecule and the radical cation. This finding also confirms the results of detailed ab initio and semiempirical calculations, which show that H 2 CO 3 should be stable in the gas phase because the activation energy for its decomposition is large.