Robert T. O’Connor

Application of infrared spectrophotometry to fatty acid derivatives

D URING the last four years the technical literature of fats and oils has included a number of papers dealing with the use of infrared spectroscopy as a tool for qualitative identification, quantitative determinations, and the elucidation of chemical structures of fat ty acid materials. A chronological listing of the most important dates in the history of the development of the applications of infrared absorption spectroscopy to fat ty acid derivatives has been prepared to illustrate the phenomenal growth in this development, particularly since 1950 (Table i) .

The aldehydes produced during the autoxidation of cottonseed oil

SummarySpectrophotometric evidence was obtained that Δ2 and Δ2:4 aldehydes are produced during the autoxidation of cottonseed oil.The unsaturated carbonyls were converted into semicarbazones and 2,4-dinitrophenylhydrazones whose characteristics indicated that the oxidation of cottonseed oil produces Δ2:4-decadienal, Δ2-octenal, and hexanal.Although the exact mechanism of their formation has not been established, these aldehydes are believed to result from the decomposition of the isomeric hydroperoxides of linoleic acid, the principal fatty acid constituent of cottonseed oil.

The infrared spectra of saturated fatty acids with even number of carbon atoms from caproic, C6 (Hexanoic), to stearic, C18 (Octadecanoic), and of their methyl and ethyl esters

SummaryInfrared spectra from 1 to 12 microns have been obtained for 7 of the homologous series of monobasic, straight-chain, saturated fatty acids of even carbon atom content from C6 to C18 and of their methyl and ethyl esters.Infrared data are presented as plots of the percentage transmission against the wavelength in microns on a linear wavelength scale for each compound, and the exact wavelength positions of maxima of the 11 most prominent bands are tabulated.Correlations of each of these bands with molecular structure are given.Methods for distinguishing the acids from the esters and of differentiating an ethyl ester from a methyl ester by observation of infrared spectra are described.An explanation, supported by earlier work with deuterium-substituted compounds, is given to account for the nonappearance, in the spectra of the fatty acids of any absorption attributable to either the free O—H group or the bonded O—H... O group.Evidence has been accumulated which indicates an association of some sort of the esters and that this association probably involves the carbonyl and the methyl groups.Data are presented to show which of the bands in the infrared spectra do and which do not follow Beer’s law.

Recent progress in the applications of infrared absorption spectroscopy to lipid chemistry

Scores of other applications of infrared spectra to problems of lipid chemistry could be cited. No useful purpose would be served by a somewhat repetitious listing of the many applications which have been reported. An attempt has been made to select applications that would represent the various ways in which infrared absorption spectroscopy is being used for and by the fatty acid chemist. A review of this nature a decade ago could easily have included a complete bibliography with reference to all papers which appeared within the period covered. This is no longer practical as infrared spectroscopy has become a major tool of the lipid chemist. In this review the reports by several workers of very excellent research contributions have not been included.ConclusionsScores of other applications of infrared spectra to problems of lipid chemistry could be cited. No useful purpose would be served by a somewhat repetitious listing of the many applications which have been reported. An attempt has been made to select applications that would represent the various ways in which infrared absorption spectroscopy is being used for and by the fatty acid chemist. A review of this nature a decade ago could easily have included a complete bibliography with reference to all papers which appeared within the period covered. This is no longer practical as infrared spectroscopy has become a major tool of the lipid chemist. In this review the reports by several workers of very excellent research contributions have not been included.During the past five years several review papers have appeared. In the second edition of Markley’s “Fatty Acids” the subject of infrared absorption is covered to about 1958 (95). In German and excellent review has been written by Kaufmann, Volbert, and Mankel (60), including 249 literature references and again covering the period through about 1958.

Atomic absorption spectroscopy

Atomic absorption spectrophotometry has been used for the rapid determination of various metallic and nonmetallic elements in crude and refined vegetable oils and in animal fats, many present in levels of parts per million. Various types of crude and refined vegetable oils were analyzed for Ca, Cu, Fe, Mg, Mn, P and Zn. This method of analysis has proven to be less time consuming, as accurate and more convenient than other spectroscopic techniques for elemental analyses.A method and apparatus for carrying out atomic spectroscopy, and particularly atomic absorption and atomic fluorescence spectroscopy. The method involves passing the emission spectrum of a light source through an atomized sample, changing the relationship between a selected emission line of the emission spectrum and a corresponding absorption line of the atoms of interest and measuring the absorption of that emission line by the sample before and after the aforementioned change in relationship. The change in emission and absorption line relationship can be effected by application of the Zeeman Effect, Stark Effect, or Doppler Effect. The apparatus, in one form, includes an electro-magnet operative to apply a magnetic field to the atomized sample and thereby cause splitting and shifting of the aforementioned absorption line, and the magnet is modulated to effect periodic variation of the spectral line relationship.

Improved method for determining gossypol in crude cottonseed oils

SummaryThe p-anisidine method for the determination of gossypol in crude cottonseed oils has been reinvestigated and modified to make it applicable to all crude oils obtained by the newer methods of processing cottonseed. The modifications included a change in the composition of the solvent, a higher reaction temperature, and the use of a more concentrated panisidine reagent. The modified method was found satisfactory where different colorimeters and spectrophotometers were used for measuring the color developed.Comparison of aniline and p-anisidine as reagents for the analysis of gossypol pigments showed that the presence of modified gossypol in some crude oils resulted in an over-correction for background absorption and led to significant errors when aniline was used as the color development agent.

The reaction of acrylonitrile and fumaronitrile with alpha-and beta-eleostearates. Plasticizer properties of the n-butyl esters of the adducts

SummaryAcrylonitrile and fumaronitrile have been employed as dienophiles in the Diels-Alder reaction with butylalpha- andbeta-eleostearates, and infrared and ultraviolet spectra determined for the addition product as well as for the dienophiles.The adducts have been tested as primary plasticizers for vinyl resins and compared with dioctyl phthalate. The fumaronitrile adducts were found superior to the acrylonitrile adducts with regard to compatibility; however the latter are satisfactory as secondary plasticizers. By incorporating the acrylonitrile adducts with DOP or TCP, it is possible to achieve either a reduction in volatility of DOP plasticized stocks or an improvement in the modulus and low-temperature performance of TCP plasticized stocks. This does not entail any sacrifice in the desirable plasticizing characteristics of DOP or TCP.

Ultraviolet absorption spectroscopy

ConclusionsIn a single lecture on a subject as big as ultraviolet absorption spectroscopy as applied to fats and oils, the contributions of many, many workers cannot even be mentioned. most of the techniques and much of the mass of useful data which have been accumulated represent contributions from scores of research workers. in this lecture only a few have been cited as examples of what ultraviolet absorption spectroscopy can do—what it is doing for the fat and oil chemist.As one hears more about newer techniques in spectroscopy, infrared absorption, microwave spectroscopy, nuclear magnetic resonance spectroscopy, etc., he is likely to think of ultraviolet absorption as an older technique which has probably made its contribution and is now to be relegated to “classical methods.” Nothing could be further from the actual picture today. As newer techniques open up a greater understanding of the chemistry of fats and oils, of their constitution, of the mechanisms of their chemical reactions, ultraviolet absorption spectroscopy will be called upon to make on ever-increasing contribution. Newer techniques to obtain pure components, such as improved chromatography, countercurrent distribution separations, etc., will also make greater and greater demands upon the use of ultraviolet absorption spectra. As long as fatty acid chemistry deals with constituents which either contain conjugated unsaturation, or unsaturated linkages which can be conjugated, either accidentally or by design, ultraviolet absorption spectroscopy will remain its most valuable tool.

Pigments of cottonseed. IV. Gossypurpurin, a purple pigment related to gossypol

SummaryGossypurpurin was prepared from gossypol via diaminogossypol, and its properties compared with gossypurpurin isolated from cottonseed pigment glands. A tentative molecular formula for synthetic gossypurpurin, C30H32O7N, has been proposed on the basis of its elementary composition. The native pigment could not be obtained in the same degree of purity as the synthetic product and the analytical data could therefore not be brought into exact agreement for the two products. However solutions of both pigments in chloroform exhibit almost identical absorption spectra and identical antimony trichloride tests. Qualitative reactions seem to indicate that the functional groups of both native and synthetic gossypurpurin are identical, and the ready conversion of both products to gossypol upon contact with acid seems to indicate that their basic structures are similar.

Report of the Instrumental Techniques Committee, AOCS, 1971–1972

As described in this report, the Instrumental Techniques Committee has in various stages of progress several methods which will be proposed for adoption as official methods of the AOCS. For convenience, these proposed methods and their present status are summarized in Table II.