Solid state and theoretical evaluation of beta-fluoroethyl esters indicate a fluorine-ester gauche effect

C R S Briggs, D O'Hagan, H S Rzepa, A M Z Slawin

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)

Abstract

Single crystal X-ray diffraction studies and a theoretical analysis indicate a preferred conformation for O-beta-fluoroethyl esters, where the C-F and C-O(CO) bonds are gauche rather than anti to each other. The O-C-C-F dihedral angles for three compounds and five independent structures indicate a range of only 63.4-69.6degrees. Evaluation of a rotational energy profile around this bond in a model system (beta-fluoroethyl acetate) predicted a similar dihedral angle and the gauche conformation to be the minimum on the rotational energy profile. High level ab initio calculations measured the gauche conformer to be 0.95 kcal mol(-1) lower in energy than the anti conformer and application of a solvation model further increased this differential to 1.6 kcal mol(-1), consistent with a previous solution state (NMR) evaluation of this system. (C) 2003 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)19-25
Number of pages7
JournalJournal of Fluorine Chemistry
Volume125
DOIs
Publication statusPublished - 1 Jan 2004

Keywords

  • gauche effect
  • beta-huoroethyl ester
  • stereoelectronic effects
  • X-ray crystal structure
  • ab initio calculations
  • 1,2-DIFLUOROETHANE
  • BOND
  • BARRIERS
  • ROTATION

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