Barrier to Rotation (ΔG‡)
Free-energy barrier that separates enantiomeric conformers/atropisomers.
Context: Determines isolability of atropisomers and labeling requirements.
Example: ΔG‡ > ~25 kcal/mol gives isolable atropisomers at room temperature.
Related Terms: Atropisomerism, Enantiomerization.
Reference: Eliel & Wilen (1994).
Bioactive Conformation
The conformation adopted by a ligand when bound to its target.
Context: Guides conformational constraint strategies to improve selectivity.
Example: Locked isostere mimicking bound pose.
Related Terms: Conformation, Pharmacophore.
Reference: Silverman (2014).
Bite Angle
Angle between donor atoms of a bidentate ligand at the metal center.
Context: Modulates enantioselectivity and reactivity in catalytic cycles.
Example: Wide-bite vs narrow-bite diphosphines.
Related Terms: Quadrant Model, Chiral Ligand.
Reference: van Leeuwen, Coordination Chemistry Reviews (1999).
Bürgi–Dunitz Angle
Preferred trajectory (~107°) of nucleophile approach to a carbonyl.
Context: Rationalizes facial selectivity and reaction rates.
Example: Hydride addition to ketones.
Related Terms: Felkin–Anh, Cram’s Rule.
Reference: Bürgi & Dunitz, JACS (1973).