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<p>Cyclopropane is introduced in this computational study as a framework for obtaining contracted carbon–chlorine and carbon–bromine bond lengths, utilizing the M06-2X/aug-cc-pVTZ method/basis set combination. For chloro- and bromocyclopropane, placing a nitro group on the same carbon as the chlorine or bromine and two fluorines in the 2 and 3 positions closest to the larger halogen leads to three 1,4-intramolecular interactions with the chloro and bromo substituents, with computed C–Cl and C–Br bond lengths of 1.711 and 1.872&#xa0;Å, respectively. Adding more fluorines to this framework does not lead to shorter carbon–chlorine or carbon–bromine bond lengths because of what has been labeled the “Teflon effect”; as more fluorines are added, they become less negative or even positive. The Coulombic interpretation of the above-mentioned bond contractions is supported by computed electrostatic potentials.</p>

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Short halogen-carbon bonds in 1-chloro- and 1-bromo-1-nitro-2,3-difluorocyclopropanes: Synergistic 1,4-intramolecular interactions?

  • 期刊论文

  • 发表日期：

    2025年10月22日

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  • Ponnadurai Ramasami,
  • Goedele Roos,
  • Jane S. Murray

摘要

Cyclopropane is introduced in this computational study as a framework for obtaining contracted carbon–chlorine and carbon–bromine bond lengths, utilizing the M06-2X/aug-cc-pVTZ method/basis set combination. For chloro- and bromocyclopropane, placing a nitro group on the same carbon as the chlorine or bromine and two fluorines in the 2 and 3 positions closest to the larger halogen leads to three 1,4-intramolecular interactions with the chloro and bromo substituents, with computed C–Cl and C–Br bond lengths of 1.711 and 1.872 Å, respectively. Adding more fluorines to this framework does not lead to shorter carbon–chlorine or carbon–bromine bond lengths because of what has been labeled the “Teflon effect”; as more fluorines are added, they become less negative or even positive. The Coulombic interpretation of the above-mentioned bond contractions is supported by computed electrostatic potentials.