We find that formic acid (FA) is very effective at facilitating diol formation through its ability to reduce the barrier for the formaldehyde (HCHO) hydrolysis reaction. The rate limiting step in the mechanism involves the isomerization of a prereactive collision complex formed through either the HCHO center dot center dot center dot H2O + FA and/or HCHO + FA center dot center dot center dot H2O pathways. The present study finds that the effective g barrier height, defined as the difference between the zero-point vibrational energy (ZPE) corrected energy of the transition state (TS) and the HCHO center dot center dot center dot H2O + FA and HCHO + FA center dot center dot center dot H2O starting reagents, are respectively only similar to 1 and similar to 4 kcal/mol. These barriers are substantially lower than the similar to 17 kcal/mol barrier associated with the corresponding step in the hydrolysis of HCHO catalyzed by a single water molecule (HCHO + H2O + H2O). The significantly lower barrier heights for the formic acid catalyzed pathway reveal a new important role that organic acids play in the gas phase hydrolysis of atmospheric carbonyl compounds.