The Burgi-Dunnitz Angle:
The Burgi-Dunitz angle describes the approach of a nucleophile (Nu) to an 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 jmol plugin to measure the angles in the 3-D moleucles below. Double-click on the first atom, single-click on the second, and double-click ont the third.
Symmetrical Ketone: Addition of OH- to Acetone
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Aldehyde or Unymmetrical Ketone: Addition of OH- to Acetaldehyde
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