A density functional theory computational chemistry exercise on the structure and vibrational spectrum of the carbene hydroxymethylene is presented. The potential energy curve for the decomposition reaction of the carbene to formaldehyde and the geometry of the transition state are explored. The results are in good agreement with recent experimental studies on the synthesis and trapping of hydroxymethylene in low-temperature, rare-gas matrices. The calculations are easy to perform and increase student understanding of a variety of important concepts in the undergraduate chemistry curriculum such as the octet rule, formal charge, VSEPR theory, bonding, vibrational spectroscopy, tunneling, transition states, and potential energy curves. The exercise nicely illustrates the power and versatility of computational chemistry methods. (Contains 3 tables and 1 figure.)