X-Ray diffraction study of sodium soaps of monounsaturated and polyunsaturated fatty acids

X-Ray powder diffraction patterns of the sodium soaps of 14 monounsaturated and polyunsaturated fatty acids were obtained at room temperature. The patterns of the soaps of 9,12-trans,trans-octadecadienoic acid, 11,14-cis,cis-eicosadienoic acid 11,14,17-allcis-eicosatrienoic acid and 5 monounsaturated fatty acids were typical of the crystalline lamellar phase. The patterns of the soaps of 9,12-cis,cis-octadecadienoic, allcis-9,12,15-octadecatrienoic, allcis-8,11,14-eicostrienoic, allcis-5,8,11,14-eicosatetraenoic, allcis-5,8,11,14,17-eicosapentaenoic and allcis-4,7,10,13,16,19-docosahexaenoic acids were indicative of the less ordered forms reported for sodium oleate at elevated temperature. The diffraction data from the less ordered soaps are consistent with the melted form of the hydrocarbon chains of the unsaturated acids at room temperature.