Publication Date:
2014-01-08
Description:
The syntheses of palmitic acids and a nonadecane are reported with CF 2 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-CF 2 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 °C). It emerges that 6c , with the CF 2 groups placed 1,4- to each other, has a significantly higher melting point (89.9 °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 CF 2 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. Beilstein J. Org. Chem. 2014, 10, 18–25. doi:10.3762/bjoc.10.4
Keywords:
difluoromethylenefatty acidsfluorinationorganic fluorine chemistryorgano-fluorinepalmitic acid
Electronic ISSN:
1860-5397
Topics:
Chemistry and Pharmacology
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