2,4-Pentanedione, also called acetylacetone (Hacac) is a precursor that has been considered for copper etching, or as a carrier for copper in copper deposition. Generally, 2,4-pentanedione is less effective than other similar molecules. In this article, temperature-programmed desorption was used to examine the decomposition of acetylacetone adsorbed on clean and oxygen precovered Cu (210) to see if we could understand how the chemistry of 2,4-pentanedione is different than that of another species, hexafluoroacetylacetone. On the clean surface, several reaction pathways were found including decomposition and desorption of 2,4-pentanedione. Most notable was that 2,4-pentanedione lost a methyl group below 300 K. By comparison hexafluoropentanedione is stable on an oxidized copper surface to 600 K. These results show that 2,4-pentanedione decomposes at temperatures below that for formation of volatile copper species. In contrast, hexafluoropentanedione is stable to temperatures above where the volatile copper species desorbs. We suggest that the difference in stability of the two molecules leads to the difference in etching characteristics that has been observed previously.