The products from the metathesis reactions of methyl and ethyl oleate were isolated using column chromatography. The various components obtained were characterized using infrared (IR), 1Hand 13C nuclear magnetic resonance spectroscopy (NMR) and gas chromatography mass spectrometry (GC-MS

Buang, Nor Aziah

Kamaruddin, Rose aini

Mohammad Nordin, Nor Asyikin

Universiti Putra Malaysia Institutional Repository

Pertanika J. Sci. & Techno\. 2(1): 55-64 (1994)ISSN: 0128-7680© Universiti Pertanian Malaysia PressThe Isolation and Spectroscopic Characterization ofProducts from the Metatheses of Alkyl OleatesRose Aini Kamarudin, Nor Asikin Mohamad Nordinand Nor Aziah BuangDepartment of Chemistry,Faculty ofScience,Universiti Teknologi Malaysia,Lockbag 791, 80990johor Bahru, Malaysia.Received 17 April 1993ABSTRAKHasil daripada tindak balas metatesis metil oleat dan etil oleat ~ipisahkandengankromatografi turus. Komponen berasingan yang diperolehi dicirikan denganmenggunakan spektroskopi infra merah, RMN IH dan RMN 13C dan kromatografigas yang digandingkan dengan spektrometer jisim.ABSTRACTThe products from the metathesis reactions of methyl and ethyl oleate wereisolated using column chromatography. The various components obtained werecharacterized using infrared (IR), 1Hand 13C nuclear magnetic resonancespectroscopy (NMR) and gas chromatography mass spectrometry (GC-MS).Keywords: metathesis, homogeneous catalyst, separation, characterization, gaschromatography, spectroscopyINTRODUCTIONIn general, the metathesis reaction of unsaturated hydrocarbons can berepresented by equation 1.R1 H R2 HR 1 /R2"c/ ""-c/'\l:::::=C/ " II+ IIH H /C" C~R/"+ ~ Ra H 4 HRa/R4"-C=CH/ ""-H (1)Rose Aini Kamarudin, Nor Asikin Mohamad Nordin and Nor Aziah BuangA variety of catalysts, both homogeneous and heterogeneous, have beenused to catalyse the above metathesis reaction. The most active are those basedon the transition metals; W, Mo, and Re (Boe1houwerand Mol 1985; Boelhouweret. al. 1972, 1974). A catalyst system for homogeneous metathesis is generallycomposed of a principal catalyst and a co-catalyst. The most successfulcombination for the metathesis of functionalised olefins is the mixed oxidecatalyst, Re20/Al20 3-MR4 (M = Sn or Pb; R = Me, Et or Bu) which wasdiscovered by Xu et. at. (1985). This system, however, is a heterogeneoussystem.The metathesis of alkyl oleate yielded 9-octadecene and the diester(Equation 2).2COORalkyl ester9-octadecene+diester(2)So far, very few studies on the separation of the metathesis reaction mixtureshave been reported (Tsuji and Hashiguchi 1980).. The diesters have been shown to have many uses. They can be convertedto polyesters and polyamides. Both polymers have been used successfully asstationary phases in gas liquid chromatography for the separation of unsatu-rated hydrocarbons and mono- and dicarboxylic esters (Boelhouwer and Mol1985). The diester can also be converted to civetone which is an important basematerial for the perfume industry (Tsuji and Hashiguchi 1980).The objective of this research was two-fold :-(i) to separate the products of metathesis of methyl and ethyl oleate usingcolumn chromatography.(ii) to identify the separated products using JR, lH and 13C NMRspectroscopy.MATERIALS AND METHODSThe infrared spectra were recorded on a Perkin Elmer PE 727B as a thinfilm. Both IH and 13C NMR spectra were recorded in CDCl3on aJEOL FX-56 Pertanika J. Sci. & Techno!. Va!. 2. No.1, 1994The Isolation and Spectroscopic Characterization of Products from the Metatheses of Alkyl Oleates400 operating at 400 MHz with TMS as internal standard. The mass spectraof the compounds were analysed by a Hewlett Packard HP 5917A usingChemstation software with a Wiley library search. The capillary column usedin this analysis was 35% methylphenyl silicone. Operating oven temperaturewas 70 - 270°C. Column chromatographywas carried out on a silica gel column.Methyl oleate and ethyl oleate were purchased from TCI and Aldrichrespectively, were of99% purity and were used without purification. No otherisomers of these compounds were found based on the gas chromatographicanalysis. The catalyst, tungsten hexachloride, and the co-catalyst, tetramethyltin,were purchased from Aldrich. The former was purified by fractional subli-mation under vacuum. Chlorobenzene from Merck was used as solvent afterprior purification by distillation over phosphorus pentoxide. All reactionswere carried out under nitrogen.General Procedure for the Metathesis ReactionThe alkyl oleate (l g) in PhQ (5.00 ml) was degassed 34 times in a round three-neck bottle flask. A solution of the catalyst in PhCI (0.20 g solution preparedas 0.03 mol/50 ml) and the co-catalyst (0.18 g) was added. The reactionmixture was heated at 70°C for 24 hours and the reaction terminated by air.The purple mixture obtained was filtered, dried and analysed by columnchromatography using silica gel with hexane: ether (25:1) as the initial solventand 25 : 4 as the final solvent.RESULTS AND DISCUSSIONIn this studyWCI6/SnMe4 catalystsystemwas used to metathesise methyl oleateand ethyl oleate. These reactions have been reported before in the literature(Boelhouwer et. ai. 1974). The objective of this study was two-fold. Firstly, toisolate the different products from the metatheses of alkyl oleates and sec-ondly, to identify and confirm each product isolated using spectroscopicmethods.Throughout this study all products were isolated by column chromatogra-phyusing silica gel. No yields are given as the main concern was to isolate andconfirm the products of the metathesis reactions by various spectroscopictechniques.Both systems used hexane:ether (25:1) as eluent. Two fractions werecollected and on increasing the polarity of the eluent (hexane:ether 25:4), athird fraction was eluted All the fractions collected were subjected to analysesby GC-MS, IR and NMR.GC-MS AnalysesThe GC-MS chromatograms from the metathesis products ofmethyl and ethyloleates before separation by column chromatography were examined. Fourpeaks were observed in both chromatograms. Upon separation by columnchromatography, three fractions were isolated for both systems. The m/zPertanika J. Sci. & Technol. Vol. 2. No. I, 1994 57Rose Aini Kamarudin, Nor Asikin Moharnad Nordin and Nor Aziah Buangvalues obtained for each fraction which contained the differentpeaks from GG-MS analyses are given in Tables1(a) and l(b).TABLE I(a)m/z values for the different fractions collected from the metathesisofmethyl oleateFractions Peaks Methyl Oleate Retention TimeSystem (min)1 I 252 24.5502 2 296 30.3243 296 33.9203 4 340 35.391TABLE I(b)m/z values for the different :fractions collected from themetathesis of ethyl oleateFractions Peaks Ethyl Oleate Retention TimeSystem (min)I I 252 24.5662 2 310 31.4323 310 34.9043 4 368 37.566Based on the m/z values obtained from GG-MS analysis, fraction 1 contains 9-octadecene, fraction 2 contains alkyl ester (starting material) and its isomerand fraction 3 contains the diester. Peak 3 is proposed to be an isomer ofalkyloleate and it is probably the trans- isomer.IRSpectraThe IR spectra of the three fractions isolated were recorded as neat liquid andare similar to those of 9-octadecenedioate, dimethyl 9-octadecenedioate anddiethyl9-octadecenedioate as reported in the literature (Tsuji and Hashiguchi1980). All the spectra showed the presence ofcis (724-740 cm-l) and trans (966-969 cml) C==C and for the diester an absorption band due to C==O stretchingwas also observed at 1739-1741 cml. The identification of the three com-pounds was further confirmed by their lH and 13C spectra.1Hand l3e NMR SpectraThe IH and 13C NMR spectra of fraction 1 are shown in Fig. 1 and Fig. 2.Alkenic protons are observed at 8 5.45 p.p.m. in the lH NMR spectrum.Resonances due to the methylene protons bonded to alkenic carbons at 858 Pertanika J. Sci. & Techno!. Vol. 2. No. I, 1994The Isolation and Spectroscopic Characterization of Products from the Metatheses of Alkyl Oleates2.0 p.p.m.(m), methyl protons at 8 0.9 (t,J - 7 Hz) and the rest of the CH2protons in the structure were observed at 8 1.3 p.p.m. (br. s).g-octadeceneCH,(12H).c=cH/ '!i.(1HIc=c/ ,CH 2 c~(2HI(3H)Fig. 1. I H NMR spectrum of9-octadecene9-0ctadeceneCH3(CH217CH = CH(CH217 CH3CDCr,IFig. 2. HC NMR spectrum of 9-octadecenePertanika J. Sci. & Techno!. Vo!. 2. No. I. 1994IIS9Rose Aini Kamarudin. Nor Asikin Mohamad ordin and Nor Aziah BuangThe 13C NMR spectrum of fraction 1 showed the presence of 9 carbons.An alkene carbon was obsel\led at 8 130.43, seven methylene carbons at 822.79 - 32.74 and a methyl carbon at8 14.16 p.p.m. The presence ofashorterpeak at 8130.43 may imply the presence of the other isomer of9-octadecene.The assignment for the different types of carbon atoms obsel\led in fraction1 is consistent with that of 9-octadecene.The I H NMR spectrum offraction 3 from the metathesis of methyl oleateis given in Fig.3. Examination of the I H NMR spectrum showed the presenceof 18 protons. A multiplet at 8 5.35 p.p.m. for an alkenic proton, a singletat 83.65 p.p.m due to a methoxy group, a multiplet centred at 82.29 p.p.m.due to a methylene group next to a carbonyl group, two very broad singletsat 8 1.97 and 8 1.62 respectively assigned to the CH2 protons bonded to thealkenic carbons and a broad singlet at <5 1.43 due to the rest of the methyleneprotons were obsel\led in the IH NMR spectrum. The presence of two verybroad singlets for the CH2 protons implies that the compound may be presentin both the cis and trans forms. From the IH NMR spectrum, the isomersexist in equal amounts.IDimethyl9-0ctadecenedioateCH,CH(CH217COOCH3 0 (10HlII II I~CH(CH2)7COOCH3 eOCH:J(3H)c=c I/ "-CH 2 CH 2 iII0 (2H) (2H) IIII iJjH/C~ MeOC c~(2H)(1H)-- --;:.±--.. ., PO""""" ,9 3 7 5 5 4 3 2 1"Fig. 3. 1H NMR spectrum ofdimethyl diesterThe 13C NMR spectrum of fraction 3 is shown in Fig. 4. The spectrumshowed the presence ofa keto group at8174.18, an alkenic carbon at8130.32,a methoxy carbon at 8 51.37 and the seven methylene carbons at8 24.96-38.55p.p.m. Both the IH and 13C NMR spectra obsel\led for fraction 3 are inagreement with the compound dimethyl 9-octadecenedioate.60 Perlanika J. Sci. & Technol. Vol. 2. No. I. 1994The Isolation and Spectroscopic Characterization of Products from the Metatheses of Alkyl Oleates,--------------------------7CH,-------,Diethyl9-0ctadecenedioate'c=c//' '-CDC~ II I."PM·"·I· .. t1·I""'I""' .. ,ltl.fTTTflTlTTTTTT~I" .."·il'·"I""' .. fTTTTT"'"T~fTT'ITTTTT~fT"T7TTTTI'j,1" •. ·1'.11' .• " .... ,[".1210 200 190 leo 170 ieo 150 14::1 1::~ 120 11C 10:'0 90 20 70 E(I =0 40 '=C 2,: 10 aFig. 4. He NMR spectrum ofdimethyl diesterThe structural assignment for fraction 3 as dimethyl 9-octadecenedioatewas further confirmed by its 2-D heteronuclear COSY spectrum (Fig. 5). Thealkenic carbons at (5130.13 p.p.m. were correlated to the alkenic proton at 85.3 p.p.m. The methyl carbon at 851.4 p.p.m. was correlated to the methoxyprotons at8 3.7 p.p.m. The methylene carbon adjacent to the carbonyl groupwas correlated to the methylene protons adjacent to the carbonyl group. TheCOSY spectrum confirmed the presence of a symmetrical diester, dimethyl 9-octadecenedioate, in fraction 3.The lHNMR spectrum offraction 3 from the metathesis of ethyl oleate issimilar to that ofdiethyl9-octadecenedioate as reported in the literature (Tsujiand Hashiguchi 1980). This is shown in Fig. 6. An examination of the I H NMRspectrum showed the presence of alkenic protons which appeared as amultiplet at (5 5.37, methylene protons of the ethoxy group appeared as aquartet centred at 84.12 0= 7 Hz), methylene protons bonded to a keto groupappeared as a triplet at 82.28, two broad multiplets centred at 81.96 and 81.61respectively and another set of multiplets centred at 8 1.25 p.p.m. due to themethylene protons in the molecule. The multiplet centred at81.96 and (51.61p.p.m. as in the case ofdimethyl9-octadecedioate implied the presence ofbothcis and trans isomers and again the isomers are present in equal amounts.Pertanika J. Sci. & Techno!. Vo!. 2. No. I, 1994 61Rose Aini Kamarudin, Nor Asikin Mohamad Nordin and Nc.r Aziah BuangI II I:UIIiI Itl-i ,, II 1 i.. It I~,01'1'" I- -I I14::' 130 I~ 110'I' 0 I' I I' oj I 'tlnf"T""T""1T'. f.1C:;:9C~7060~ 4O?~@1::Fig. 5. 2 - D COSY heteronucleus spectrum ofdimethyl 9-octadecenedioateDiethyl9-0ctadecenedioateoICC!3CHJ(2H)ISCH2 & CH2C~(13H)62, ~Fig. 6. 1H NMR spectrum ofdiethyl diesterPertanika J. Sci. & Technol. Vol. 2. No. I, 1994The Isolation and Spectroscopic Characterization of Products from the Metatheses of Alkyl OleatesThe 13C NMR spectrum of fraction 3 from the metathesis of ethyl oleatesystem is shown in Fig. 7. The spectrum showed the presence of a keto group(8173.85), alkenic carbon (8130.32), methylene carbon of an ethoxy group(860.13), methyl carbon on an ethoxy group (8 14.27) and the rest of themethylene carbons (8 24.98 - 8 34.37). Both the IH and 13C NMR datasupported the presence of a symmetrical diester, diethyl 9-octadecenedioate,in fraction 3 of the metathesis product from the ethyl oleate system.Dimelhyl9-0cladecenedioaleCOC~oIII COCH,£H,II!!iIIIiI_,~LUr:TT'TTTTTI"(TTTT"'TTTl""""'"'"""I"it", i1 i"" .. '''I'' .. 'ti·i''tl ••(''li,jI· .. I''',· .. 'l'· .. '''''I'' .... "~l"·"'''·I''''''''·~I·iljiil''I··''''·I''''''·I .. ·i~~'1~:c 1~ 1=<) 170 1l:V 15:1 14(· EO 120 111) IX 9\) ~o ia EO ::c 4(\ 2: :::0 l~ 0Fig. 7. He NMR spectrum ofdiethyl diesterCONCLUSIONThe products from the metatheses ofmethyl oleate and ethyl oleate have beensuccessfully separated by using column chromatography to give three compo-nents, i.e. 9-octadecene, starting material and diester. The two products havebeen characterized based on their GG-MS, JR, lH and I3C NMRspectra. Basedon their IH NMR spectra, the ratio of the cis to trans isomer in both the diestersis about 1:1.ACKNO~DGEMENTSThis research was funded partly by the Ministry of Science and Technologyunder the Sixth Malaysia Plan. One of the authors (RAK) was awardeda research fellowship from Rikkyo University to carry out part of the researchin collaboration with Profesor Horiuchi Akira at the Department ofChemistry,Pertanika J. Sci. & Techno!. Vol. 2. No. I, 1994 63Rose Aini Kamarudin. Nor Asikin Mohamad Nordin and Nor Aziah BuangRikkyo University. Special thanks to Profesor Horiuchi for recording theIH and 13C NMR spectra.REFERENCESBOELHOUWER, C. and J.C. MoL. 1985. Metathesis reactions of fatty acids. Prog. Lipid Res.32: 243.BOELHOUWER, C., F.P.B. VAN DAM and M.C. MITI'ELMEIJER. 1972. Metathesis of unsaturatedfatty esters by a homogeneous tungsten hexachloride-tetra-methyltin catalyst.J Chern.Soc., Chern. Commun. 122.BOELHOUWER, C., F.P.B. VAN DAM and M.C. MlTIELMEIJER. 1974. Homogeneous catalyticmetathesis of unsaturated fatty esters - new synthetic method for preparation ofunsaturated monocarboxylic and dicarboxylic acids. J Amer. Oil Chern. Soc. 51: 389.TSl[JI, T. and S. HAsHIGUCHI. 1980. Application of olefin metathesis to organic synthesis.Synthesis of civetone and macrolides. Tet. Lett. 2955.Xu XIAODlNG, P. IMHOFF, G.C.N. VAN DEN AARnWEG and C. MoL. 1985. Mixed-oxide catalystsfor the methathesis of functionalized alkenes. J Chern. Soc. Chern. Commun. 273.64 Pertanika J. Sci. & Techno!. Vol. 2. No.1, 1994

The Isolation and Spectroscopic Characterization of

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The Isolation and Spectroscopic Characterization of Products from the Metatheses of Alkyl Oleates

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