Structurally diagnostic ion/molecule reactions: class and functional-group identification by mass spectrometry.

This article discusses the application of gas-phase ion/molecule reactions for fine structural elucidation in mass spectrometry. This approach is illustrated via a representative collection of class- and functional group-selective reactions, a few of historical relevance as well as by more recent and instructive examples, and their applications. The focus is on reactions performed under well-controlled conditions of sequential mass spectrometry, discussing key mechanistic details and potential applications. Recent and innovative strategies that allow these reactions to be performed under ambient conditions, making this fast, selective and sensitive approach for structural investigation much more generally applicable, are also discussed.