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The Bürgi-Dunitz angle describes the oblique approach of a nucleophile toward a carbonyl carbon, conventionally measured relative to C=O. A typical trajectory is near $107^{\circ }$, with the optimum depending on the system.

Hans-Beat Bürgi coauthored the structural-correlation work associated with the Bürgi-Dunitz trajectory. Comparing close nucleophile-carbonyl contacts in crystal structures helps identify a preferred oblique approach to a carbonyl carbon.

The characteristic Bürgi-Dunitz angle connects three-dimensional geometry with orbital overlap and repulsion. It is a useful trend for understanding nucleophilic addition, while steric constraints and molecular environment can change the accessible path.^[ref]