Term: tetrahedral intermediate
https://doi.org/10.1351/goldbook.T06289

Definition:
A reaction intermediate in which the bond arrangement around an initially double-bonded carbon atom (typically a carbonyl carbon atom) has been transformed from trigonal to tetrahedral. For example, aldol in the condensation reaction of acetaldehyde (but most tetrahedral intermediates have a more fleeting existence).

Related Terms:
1) intermediate (http://doi.org/10.1351/goldbook.I03096).
2) condensation reaction (http://doi.org/10.1351/goldbook.C01238).

Source: PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1173 (https://doi.org/10.1351/pac199466051077)

Citation: 'tetrahedral intermediate' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.T06289

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