The difluoromethylene (CF2) group in aliphatic chains: synthesis and conformational preference of palmitic acids and nonadecane containing CF2 groups

Yi Wang, Ricardo Callejo, Alexandra M. Z. Slawin, David O'Hagan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

The syntheses of palmitic acids and a nonadecane are reported with CF2 groups located 1,3 or 1,4 to each other along the aliphatic chain. Specifically 8,8,10,10- and 8,8,11,11-tetrafluorohexadecanoic acids (6b and 6c) are prepared as well as the singly modified analogue 8,8-difluorohexadecanoic acid (6a). Also 8,8,11,11-tetrafluorononadecane (27) is prepared as a pure hydrocarbon containing a 1,4-di-CF2 motif. The modified palmitic acids are characterized by differential scanning calorimetry (DSC) to determine melting points and phase behaviour relative to palmitic acid (62.5 degrees C). It emerges that 6c, with the CF2 groups placed 1,4- to each other, has a significantly higher melting point (89.9 degrees C) when compared to the other analogues and palmitic acid itself. It is a crystalline compound and the structure reveals an extended anti-zig-zag chain. Similarly 8,8,11,11-tetrafluorononadecane (27) adopts an extended anti-zig-zag structure. This is rationalized by dipolar relaxation between the two CF2 groups placed 1,4 to each other in the extended anti-zig-zag chain and suggests a design modification for long chain aliphatics which can introduce conformational stability.

Original languageEnglish
Pages (from-to)18-25
Number of pages8
JournalBeilstein Journal of Organic Chemistry
Volume10
DOIs
Publication statusPublished - 6 Jan 2014

Keywords

  • Difluoromethylene
  • Fatty acids
  • Fluorination
  • Organic fluorine chemistry
  • Organo-fluorine
  • Palmitic acid
  • C-F Bbond
  • Organofluorine chemistry
  • Organic-compounds
  • Flourine
  • Derivatives
  • Reagents

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