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Journal of Computer-Aided Molecular Design

, Volume 10, Issue 3, pp 247–254 | Cite as

Comparison of conformer distributions in the crystalline state with conformational energies calculated by ab initio techniques

  • Frank H. Allen
  • Stephanie E. Harris
  • Robin Taylor
Research Paper

Summary

The conformational preferences of 12 molecular substructures in the crystalline state have been determined and compared with those predicted for relevant model compounds by ab initio molecular orbital calculations. Least-squares regression shows that there is a statistically significant correlation between the crystal-structure conformer distributions and the calculated potential-energy differences, even though the calculations relate to a gas-phase environment. Torsion angles associated with high strain energy (>1 kcal mol-1) appear to be very unusual in crystal structures and, in general, high-energy conformers are underrepresented in crystal structures compared with a gas-phase, room-temperature Boltzmann distribution. It is concluded that crystal packing effects rarely have a strong systematic effect on molecular conformations. Therefore, the conformational distribution of a molecular substructure in a series of related crystal structures is likely to be a good guide to the corresponding gas-phase potential energy surface.

Keywords

Ab initio Cambridge Structural Database Conformational energy 

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Copyright information

© ESCOM Science Publishers B.V 1996

Authors and Affiliations

  • Frank H. Allen
    • 1
  • Stephanie E. Harris
    • 2
  • Robin Taylor
    • 1
    • 3
  1. 1.Cambridge Crystallographic Data CentreCambridgeUK
  2. 2.Department of Pharmaceutical SciencesUniversity of AstonBirminghamUK
  3. 3.Zeneca AgrochemicalsJealott's Hill Research StationBracknellUK

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