Sodium decanoate mixtures

The SANS external contrast-matching technique (see Section 9.10) was employed also by Caponetti et al. [89], who concluded that a mixture of sodium per-fluorooctanoate and sodium decanoate form mixed micelles having the same composition and a very narrow size distribution. Clapperton et al. [94] examined binary mixtures of ammonium perflurooctanoate and ammonium decanoate by a combination of H- and F-NMR spectroscopy. The mixtures were buffered at pH 9.0 in NH4OH-NH4CI solutions at an ionic strength of 0.1. The chemical shift data indicated nonideal, unfavored mixing of the hydrocarbon and fluorocarbon surfactants in the micelle. 

By increasing the molar proportion of the monocarboxylic acid, the yield of (II) is improved. Thus electrolysis of a mixture of decanoic acid (n-decoic acid capric acid) (V) (2 mols) and methyl hydrogen adipate (VI) (1 mol) in anhydrous methanol in the presence of a little sodium methoxide gives, after hydrolysis of the esters formed, n-octadecane (VII), tetradecanoic or myristic acid (VIH) and sebacic acid (IX) ... 

Myristic acid (from decanoic acid and methyl hydrogen adipate). Dissolve 55-2 g. of pure decanoic acid (capric acid decoic acid), m.p. 31-32°, and 25 -6 g. of methyl hydrogen adipate in 200 ml. of absolute methanol to which 0-25 g. of sodium has been added. Electrolyse at 2-0 amps, at 25-35° until the pH of the electrolyte is 8-2 (ca. 9 hours). Neutralise the contents of the electrolytic cell with acetic acid, distil off the methanol on a water bath, dissolve the residue in about 200 ml. of ether, wash with three 50 ml. portions of saturated sodium bicarbonate solution, and remove the ether on a water bath. Treat the residue with a solution of 8 0 g. of sodium hydroxide in 200 ml. of 80 per cent, methanol, reflux for 2 hours, and distil off the methanol on a water bath. Add about 600 ml. of water to the residue to dissolve the mixture of sodium salts extract the hydrocarbon with four 50 ml. portions of ether, and dry the combined ethereal extracts with anhydrous magnesium sulphate. After removal of the ether, 23-1 g. of almost pure n-octadecane, m.p. 23-24°, remains. Acidify the aqueous solution with concentrated hydrochloric acid (ca. 25 ml.), cool to 0°, filter off the mixture of acids, wash well with cold water and dry in a vacuum desiccator. The yield of the mixture of sebacic and myristic acids, m.p. 52-67°, is 26 g. Separate the mixture by extraction with six 50 ml. portions of almost boiling light petroleum, b.p. 40-60°. The residue (5 2 g.), m.p. 132°, is sebacic acid. Evaporation of the solvent gives 20 g. of myristic acid, m.p. 52-53° the m.p. is raised slightly upon recrystallisation from methanol. 

We can proceed in the opposite direction too. Consider, for example, a mixture of 1-decanol and decanoic acid. 1-Decanol is not soluble in water and does not react with sodium hydroxide. However, decanoic acid reacts with sodium hydroxide and thus dissolves in the basic solution. 

Sharma, R., R. Pyter, P. Mukerjee, Spectrophotometric determination of perfluorocarboxylic acids (heptanoic to decanoic) and sodium perfluorooctanoate and decyl sulfate in mixtures by... 

---