The Burgi-Dunnitz Angle:

Note: to see and manipulate the 3-dimensional images in this tutorial you must have the chime plug-in.

The Burgi-Dunitz angle describes the approach of a nucleophile (Nu) to a electrophilic carbon that is either part of a carbonyl or an enolate. It is defined as the Nu-C=0 angle for carbonyl electrophiles (ketones, aldehydes, etc) and the Nu-C=C angle for enolates and related electrophiles.
Burgi, Dunitz, Lehn, Wipff Tetrahedron,1974,30, 1563.

You can use the chime plugin to measure the angles in the 3-D moleucles below. From the chime menu choose Select: Mouse Click Action: Angle and you can select the atoms to determine the angles.

Symmetrical Ketone: Addition of OH- to Acetone
The Burgi-Dunitz angle
End-on View
3-D Model

Aldehyde or Unymmetrical Ketone: Addition of OH- to Acetaldehyde
The Burgi-Dunitz angle
End-on View
3-D Model

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Created February 28, 2001. KC Russell, University of Miami
© 2001 KC Russell