Deuterium NMR spectroscopy has been used in conjunction with mass spectrometry to study the exchange reaction of the ketones acetone, butan-2-one and cyclopentanone over a variety of supported metal catalysts. In many of the experiments simple, random, stepwise exchange was prevalent. However, in certain instances multiple exchange occurred. For butan-2-one and cyclopentanone this multiple exchange was essentially limited to the ...