A simplified method for the preparation of α‐ and β‐eleostearic acids and a revised spectrophotometric procedure for their determination

Abstract

SummarySimplified methods for the preparation of pure α‐ and β‐eleostearic acids are described. These procedures involve saponification of α‐ and β‐tung oils under mild conditions, followed by direct crystallization of the liberated acids at −20°C. from ethanolic solution. Only one recrystallization from ethanolic solution at +5°C. was required to produce the pure acids.Absorptivities obtained from measurements of the ultraviolet absorption revealed α‐eleostearic acids of from 3–4% higher purity than those used in obtaining the equations previously recommended for the simultaneous determination of α‐ and β‐eleostearic acids. This has necessitated a revision of these equations. Equations for the determination of each isomer from both cyclohexane and ethanol are reported. Equations are also given for an independent determination of total eleostearic acid, and for the determination of one isomer in the absence of the other.Infrared absorption spectra in the rock salt region from 2–15 microns have been measured from potassium bromide discs. These solid‐state or crystalline spectra reveal, in addition to the prominent bands assigned to characteristic groupings of the eleostearic acid molecule, the progression bands by means of which carbon chain length can be computed.