Premium
Cis ‐Unsaturated fatty acid products by hydrogenation with chromium hexacarbonyl
Author(s) -
Frankel E. N.,
Awl R. A.,
Friedrich J. P.
Publication year - 1979
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02674144
Subject(s) - chemistry , linolenate , degree of unsaturation , soybean oil , catalysis , organic chemistry , stereoselectivity , medicinal chemistry , solvent , chromium , unsaturated fatty acid , cis–trans isomerism , conjugated system , fatty acid , food science , polymer
The use of Cr(CO) 6 was investigated to convert polyunsaturated fats into cis unsaturated products. With methyl sorbate, the same order of selectivity for the formation of cis ‐3‐hexenoate was demonstrated for Cr(CO) 6 as for the arene‐Cr(CO) 3 complexes. With conjugated fatty esters, the stereoselectivity of Cr(CO) 6 toward the trans, trans diene system was particularly high in acetone. However, this solvent was not suitable at elevated temperatures required to hydrogenate cis, trans ‐ and cis, cis ‐conjugated dienes (175 C) and nonconjugated soybean oil (200 C). Reaction parameters were analyzed statistically to optimize hydrogenation of methyl sorbate and soybean oil. To achieve acceptable oxidative stability, it is necessary to reduce the linolenate constituent of soybean oil below 1–3%. When this is done commercially with conventional heterogenous catalysts, the hydrogenated products contain more than 15% trans unsaturation. By hydrogenating soybean oil with Cr(CO) 6 (200 C, 500 psi H 2 , 1% catalyst in hexane solution), the product contains less than 3% each of linolenate and trans unsaturation. Recycling of Cr(CO) 6 catalyst by sublimation was carried through three hydrogenations of soybean oil, but, about 10% of the chromium was lost in each cycle by decomposition. The hydrogenation mechanism of Cr(CO) 6 is compared with that of arene‐Cr(CO) 3 complexes.