Summary
Complete binary freezing-point data have been obtained for each of the polymorphic modifications of acetamide with alpha-eleostearic acid and beta-eleostearic acid and for alpha-eleostearic acid with beta-eleostearic acid. In the light of previously published data the fact that all of these systems are of the simple eutectic type suggests that the tendency of the long-chain fatty acids to form 1∶1 molecular compounds with acetamide and with each other decreases as the degree of unsaturation increases.
The fact that the heat of fusion of beta-eleostearic acid, 13.2 kcal. per mole, calculated from the freezing-point data is greater than that for the alpha acid, 10.5 kcal. per mole, corroborates the conclusion that the beta acid is the trans-trans-trans modification. Calculations of heats of fusion have been made, based upon all the available freezing-point data in the literature for binary systems between pairs of C18 fatty acids of different degrees of unsaturation, and certain trends have been dsicussed.
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One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U.S. Department of Agriculture.
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Mod, R.R., Skau, E.L. & Planck, R.W. Binary freezing-point diagrams for alpha- and beta-eleostearic acids with each other and with acetamide. J Am Oil Chem Soc 30, 368–371 (1953). https://doi.org/10.1007/BF02633772
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DOI: https://doi.org/10.1007/BF02633772