Synthesis of a Palm-Based Star-Shaped Hydrocarbon via Oleate Metathesis Yuen-May Choo*, Kay-EngOoi, Ing-Hong Ooi, and Daniel D.H. Tan Palm Oil ResearchInstitute of Malaysia, 50720 Kuala Lumpur, Malaysia ABSTRACT: 10,11-Dioctyleicosane, a star-shaped hydrocar- bon, has been successfully synthesized from 9-octadecene (a product from metathesis of methyl oleate or ethyl oleate) through dimerization followed by hydrogenation. The product was determined by 13C nuclear magnetic resonance spectro- scopic and gas chromatography/mass spectrometric techniques. This hydrocarbon likely exhibits lubricating properties that can be used as high-performance functional fluids in automotive lu- brication. We also report the presence of a novel product, a trimer that was formed during the synthesis. JAOCS 73, 333-336 (1996). KEY WORDS: Diethyl 9-octadecenedioate, 10,11-dioctyl eicosane, ethyl and methyl oleates, metathesis, 9-octadecene, palm oil, star-shaped hydrocarbon. Oleochemical products such as alkyl oleates are obtained through transesterification of palm oil and palm oil products or direct esterification of oleic acid with alcohol (e.g., methanol or ethanol). Metathesis of alkyl oleates provides two main products, 9-octadecene and dialkyl 9-octadecene- dioate. In a previous paper, we have reported the synthesis of civetone from the dialkyl 9-octadecenedioate via Dieckmann condensation/hydrolysis-decarboxylation reactions (1). This paper describes the preparation of a star-shaped hydrocarbon, 10,11-dioctyleicosane. 9-Octadecene can undergo dimeriza- tion, and further hydrogenation gives rise to this saturated highly branched C36 hydrocarbon. Various catalysts are known for synthesizing various types of star-branched hydrocarbons, more generally known as hy- drogenated (~-olefin oligomers. The catalysts used include cationic, free-radical, and anionic types. Early reports showed the use of a cationic catalyst, AIC13, in preparing the l-octene oligomer (2,3). BF 3, together with a protonic co-catalyst such as RCOOH, ROH, or H20, produces hydrogenated ct-olefin oligomers, which have excellent lubricating properties (4-7). This paper reports the synthesis of 10,11-dioctyleicosane from 9-octadecene derived from palm oil and palm-based fatty acids via dimerization, followed by hydrogenation. *To whomcorrespondence shouldbe addressed at Chemistryand Technol- ogy Division, Palm Oil Research Institute of Malaysia, P.O. Box 10620, 50720 KualaLumpur,Malaysia. EXPERIMENTAL PROCEDURES Materials. WCI 6 and SnMe 4 were purchased from Aldrich Chemical Co. (Milwaukee, WI). WC16 was purified by vac- uum sublimation at 200~ Benzene, purchased from Merck (Darmstadt, Germany), was dried over CaCI 2 and distilled onto 3/~ molecular sieves. Other solvents used .were of reagent grade. Thin-layer chromatography (TLC) was per- formed on Merck Analtech glass plates precoated with silica gel (UV254, 0.25 mm thickness, Merck 9385, 230--400 mesh). Methods. 13C Nuclear magnetic resonance (NMR) spectra were obtained on JEOL JNM-PMX60 SI and JNM-FX100 spectrometers (JEOL, Tokyo, Japan) with tetramethylsilane as internal standard. Electron-impact/mass spectra (ELMS) were obtained from a JEOL JMS-DX303 spectrometer. Preparation of ethyl oleate. The preparation of ethyl oleate was carried out by transesterification of crude palm oil or di- rect esterification of oleic acid with ethanol. Transesterification of crude palm oil and palm oil prod- ucts. Transesterification of crude palm oil and palm oil prod- ucts has been well established, and detailed experimental pro- cedures have been described elsewhere (8). Direct esterification of oleic acid with ethanol. Purified oleic acid was esterified with dry ethanol in the presence of catalytic amounts of concentrated sulfuric acid at 110~ for 2 h. Water, produced during esterification, was continuously removed with a Dean & Stark distillation apparatus. Excess ethanol was distilled off at the end of the reaction. NaHCO 3 solution was added to neutralize the acid. The product was extracted with petroleum ether (60-80~ three times. The extract was then dried over NaSO 4 and filtered, and the sol- vent was removed. The pure ethyl oleate (-100%) was ob- tained by distillation under reduced pressure. Metathesis ofalkyl oleates. Metathesis of alkyl oleate to yield 9-octadecene and diethyl 9-octadecenedioate was dis- cussed in detail in a previous paper (1). 9-Octadecene. The starting material obtained in 97% yield was obtained from metathesis of ethyl oleate with catalyst WCI6/SnMe 4. 9-Octadecene was separated from other metathesis products in the earlier fraction with petroleum ether in a silica column. The IH NMR (CDCI 3) data showed the chemical shift at ~ 5.43-5.35 (m, olefinic proton, 2H), 1.99 (m, 4H), 1.27 (m, 24H), 0.94-0.83 (t, 6H); infrared (NaCI) Copyright 9 1996 by AOCS Press 333 JAOCS, Vol. 73, no. 3 (1996)