Reaction intermediates in organic chemistry — The “big picture”1

An overview of the discovery of reaction intermediates and associated concepts in physical organic chemistry is presented. Particular attention is paid to chronology of ideas, frequency of occurrence of reaction intermediates in the library of organic reactions used in organic synthesis, and the lexicon of scientific terms used in the language of physical organic chemistry. General logic decision trees are presented for the unique or near unique identification of reaction intermediates based on experimental techniques and common patterns of reactivity documented in the literature over the last century. Contributions made by scientists working in laboratories at Canadian universities and at the National Research Council of Canada are noted throughout.