Reaction paths for the chemical vapor deposition (CVD) of copper from (hfac)Cu(vtms), Cu(hfac)(2), and Cu(fod)(2) were studied using mass spectrometric analysis of the reaction products. Cu(hfac)(2) was identified as one of the products when (hfac)Cu(vtms) reacts with or without hydrogen at temperatures from 130 to 235 degrees C in a hot-wall batch reactor. Therefore, the route to copper formation is a disproportionation reaction which we found to be reversible under all operating conditions. The reverse reaction regenerates the precursor, (hfac)Cu(vtms). Our experiments show that Cu(hfac)(2) reacts very slowly with H-2 at temperatures below 250 degrees C, which typically are used for (hfac)Cu(vtms). Therefore, below 250 degrees C, the deposition rate of copper from (hfac)Cu(vtms) is not increased by the reaction of its product, Cu(hfac)(2), with hydrogen. For CVD using Cu(hfac)(2) and Cu(fod)(2) with hydrogen, Hhfac and Hfod are the reaction products.