The thermal decomposition of twenty-five cupric carboxylates was studied by mass spectrometry. In eleven cases volatile cuprous carboxylates (many of which have not been previously reported) were detected amongst the decomposition products. The cuprous carboxylates fromacetic, propionic, 11-butyric, isobutyric, difluoroacetic, trifluoroacetic, benzoic, p-fluorobenzoic, p-chlorobenzoic, o-chlorobenzoic, and pentafluorobenzoic acids were all found to be dimeric in the vapor phase. Two basically different fragmentation pathways can be proposed depending upon whether the copper salt is formed from an alkyl-or aryl-carboxylic acid. For the former, the spectra are dominated by even-electron fragment ions formed by initial loss of RCO2. from the molecular ion. For the latter, a parallel fragmentation pathway initiated by loss of COz from the molecular ion and migration of the aryl group to the metal is also present.La dCcomposition thermique de 25 carboxylates cupriques a CtC CtudiCe i I'aide de la spectrometric de masse. Dans 1 I cas, on a pu dCtecter la prisence de carboxylates cuivreux volatils (plusieurs de ceux-ci n'ont pas dCji Ct6 dCcrits) parmi les produits de decomposition. Les carboxylates cuivreux des acides acttique, propionique, 11-butyrique, iso-butyrique, difluoroacktique, trifluoroacetique, benzoi'que,p-fluorobenzoi'que, p-chlorobenzo'ique, o-chlorobenzoi'que et pentafluorobenzoi'que, se prCsentent tous sous forme dimerique en phase vapeur. Deux processus fondamentalement diffkrents de fragmentation peuvent ttre proposes selon que le sel de cuivre est form6 a partir d'un acide carboxylique alcoyle ou aryle. Pour le premier cas, les spectres se composent surtout de fragments ioniques comportant un nombre pair d'Clectrons qui proviennent de la perte initiale de RCOz . de I'ion molCculaire. Pour le second cas, un processus de fragmentation parallkle issu de la perte de COz de l'ion molCculaire et de la migration du groupe aryle au metal est aussi prCsent.[Traduit par le journal]