The McLafferty rearrangement: A personal recollection

In this article, dedicated to Professor Fred McLafferty, I wish to recollect early observations with regard to the rearrangement named after him for 1-nitropropane and the methyl ester of gamma-nitrobutyric acid. This rearrangement occurs for both cases clearly in a stepwise fashion, although for the ester, it occurs as a hidden rearrangement that catalyzes the tautomerization of the nitro group into its aci-form. (C) 2004 American Society for Mass Spectrometry.