161 Synthesis of Isooctenyl Alcohols from Diisobutylene via Chlorination* by YasuhiroFurukawa**, Koichi Asano** and YoujiKomatsu** Summary: Isooctenylalcohols were prepared from hydrolysisof diisobutylene monochlorides which were obtained by chlorinationof diisobutylene. Analysis and identificationof diisobuylene monochlorideand isooctenylalcohol and hydrolysisof the diisobutylenemonochloride to isooctenyl alcohol in the presenceof alkalis and solventswere studied. Thefollowing results were obtained. (1) Structuresof the products were determinedby the comparisonof their IR and NMR spectra with those of authentic compounds. The diisobutylenemonochloride contained 1-chloro-2-neo- pentyl-2-propene, cis-1-chloro-2,4, 4-trimethyl-2-pentene,trans-1-chloro-2, 4, 4-trimethyl-2-pentene and 3-chloro-2,4, 4-trimethyl-1-pentene,and the isooctenylalcohol contained2-neopentyl-2-propene- 1-ol, cis-2,4, 4-trimethyl-2-pentene-1-ol, trans-2,4, 4-trimethyl-2-pentene-1-oland 2, 4, 4-tri- methyl-1-pentene-3-ol. (2) Reactionconditions in the presenceof alkalis were studied. Among the alkalis used, sodium carbonate, sodium bicarbonateand calcium hydroxidegave favorable results, and the optimum pH value was in the range of 8～11. When a strong alkali such as sodium hydroxide was used, favorable results were obtained by keeping pH at 8～10. (3) DMSO was found to be one of most effectivesolvents in that the rate of hydrolysiswas high and primary isooctenylalcohols were obtained in high selectivity. (4) The kinetic studies showed that hydrolysisof monochloridewas of the SN2 type. (5) Examination of the product compositionduring hydrolysisin DMSO showed that secondary monochloridechanged to primary isooctenylalcohols by isomerization. The reactionpath of four isooctenylchlorides, which were contained in the monochloride,was discussed. monochloride and isooctenyl alcohol, and de- 1 Introduction tails of the reactions have not been clarified. Many processes are known for the preparation In the present work, the components contained of octyl alcohols, for example, n-octyl alcohol in the diisobutylene monochloride and isooctenyl by Ziegler process or high pressure reduction of alcohol were separated by fractional distillation the esters of fatty acids and 2-ethylhexyl alcohol or by preparative gas chromatography. The and isooctyl alcohols by oxo process or acetal- isolated chlorides and alcohols were identified dehyde process. On the other hand, the syn- by the comparison of their IR and NMR spectra thesis of alcohols by hydrolysis of the halogenated with those of authentic compounds which were hydrocarbons has been widely studied, particu- synthesized by unambiguous methods. The larly, hydrocarbons of lower molecular weights. hydrolysis of diisobutylene monochloride in the For higher hydrocarbons, the yields of the al- presence of alkalis and solvents were carried out, cohols are low because of the occurrence of such and the effects of reaction conditions and the side reaction as the formation of olefinic hydro- reaction path were discussed. carbons by the elimination of halogen and its hydride1). 2 Experimental The preparative method of isooctenyl alcohols 2.1 Materials through hydrolysis of diisobutylene monochloride, 2.1.1 Diisobutylene (DIB) and Chlorine which was obtained by chlorination of diiso- DIB used was a product of isobutene poly- butylene, has been described in patents2)～4). merization by sulfuric acid catalyst (Maruzen However, no studies have been made on the Oil Co.) and was purified by fractional distil- compositions and structures of the diisobutylene lation. Purity was above 99.9%. Purified DIB contained 68.4% of 2, 4, 4-trimethyl-1-pentene * Received June 11, 1973. ** Research & Development ** Center, Maruzen Oil and 31.6% of 2, 4, 4-trimethyl-2-pentene. Chlo- Co., Ltd. (Gongendo, Satte-Machi, Saitama, 340-01). rine was commercially obtained and purified by Volume 15, No. 2, November 1973 162 Furukawa, Asano and Komatsu: Synthesis of 70～75℃/12mmHg) by preparative gas chro- passing it through concentrated sulfuric acid and calcium oxide. matography (Chromosorb P/Reoplex 400=80/20 2.1.2 Diisobutylene Monochloride [I] by wt., 5mmφ×7.5mm, 175℃). B. p. 173.6 DIB was chlorinated at 90℃ by introducing ℃ (Lit.9) 72.5～73.5℃/12mmHg); d204 0.8550; gaseous chlorine in a mole ratio of 0.9 to DIB n20D1.4440 (Lit.9) 1.4441); 3, 5-dinitrobenzoate m.p. into a glass flask. The reaction product was 57,3℃ (Lit.9) 56℃). washed with water and distilled in Widmer co- 2.3.3 cis- and trans-2, 4, 4-Trimethyl-2-pente- lumn, and monochloride fraction [I] (b. p. 156～ ne-1-ol [V] and [VI] 158℃, yield 85%) was obtained. Crude ethyl-2, 4, 4-trimethyl-2-pentenoate [IX] 2.1.3 Isooctenyl Alcohol [II] obtained by Wadswarth's reaction10) involving Monochloride fraction [I] was hydrolyzed at trimethyl acetaldehyde and ethyl-α-phosphono- 150℃ for 6 hours in a 500ml autoclave with a propionate was separated into cis- and trans-iso- calcium hydroxide-water mixture with a mole mers ([VII] and [VIII], respectively) by fractional ratio of Ca(OH)2/[I] of 0.55 and the ratio of distillation. Alcohol [V] and [VI] were obtained water/[I] of 5 by weight. by the reduction of the corresponding esters Isooctenyl alcohol fraction [II] (b. p. 98～ [VII] and [VIII] with LiAlH4. 100℃/50mmHg, yield 70%) was obtained from cis-and trans-Ethyl-2,4, 4-trimethyl-2-pentenoate[VII], the reaction mixture by adding isooctane and [VIII] distilling resulting mixture. 170ml of dimethylformamide and 4.1g of 2.2 Analysis sodium hydride were introduced into a glass Conditions of gas chromatography used for flask, and while stirring the mixture, 20g of determinations of chlorides, alcohols and hy- ethyl-α-phosphonopropionate prepared from ethyl- drolysis products were as follows: α-bromopropionate and α-triethyl phosphite was 1) Determination of chlorides added. During the addition, the reaction tem- Column: PPG 0.25mmφ ×90m. Column perature was kept at 20℃ and then the reaction temp.: 90℃. Detector: FID. Carrier was continued for 1hr at room temperature. gas: He 3.0kg/cm2. To the reaction mixture, 7.2g of trimethyl- 2) Determination of alcohols and hydrolysis acetaldehyde freshly prepared from tert-butyl products chloride and methyl formate by Grignard re- Column: Reoplex 400 0.25mmφ×90m. action was added at 30℃. After continuing Column temp.: 125℃ (for alcohols), 142℃ the reaction for 1hr at room temperature and (for hydrolysis products). Detector: FID. 3hr at 80℃, the reaction mixture was hydro- Carrier gas: He 3.0kg/cm2. lyzed with 300ml of water, extracted with ethyl NMR spectra were obtained with a Nihon ether, and finally dehydrated with anhydrous Denshi Model JNM-C-60 (60MHz) spectro- sodium sulfate. The product [IX] was separated meter using tetramethylsilane as the internal into two fractions of b. p. 71～73℃/15mmHg standard in carbon tetrachloride at 25℃. (1.7g, yield 13.1%) and b. p. 83～85℃/15mmHg IR spectra were recorded by a Shimadzu (1.8g, yield 14.3%) by fractional distillation Model AR-275 infrared spectrophotometer using (4mmφ×60cm column packed with helipack, NaCl prism at 27℃. reflux ratio 1/120). 2.3 Syntheses of Standard Isooctenyl Al- NMR spectra (δ, ppm) of the former were cohols and Chlorides 5.42 (-CH=C-), 3.97～4.33 (-O-CH2-C-), 1.84 2.3.1 2,4, 4-Trimethyl-1-pentene-3-ol [III] (-C=C-CH3), 1.17～1.41 (-O-C-CH3), 1.08 (tert- Alcohol [III] was obtained by reacting me- Bu); and those of the latter were 6.68 (-CH=C-), thacrolein5),6) with tert-butyl-lithium7) followed 3.95～4.30 (-O-CH2-C), 1.90 (C=C-CH3), 1.29～ by hydrolysis. B. p. 154.7℃ (Lit.8) 154.8～155 .0 1.38 (-O-C-CH3), 1.19 (tert-Bu). NMR spectra ℃); d204 0.8556; n20D 1.4428; 3, 5-dinitrobenzoate at 5.42 showed the cis-conformation hydrogen m. p. 123.3℃ (Lit.8) 123℃). with respect to carbonyl and at 6.68 showed that 2.3.2 2-Neopentyl-2-propene-1-ol [IV] of the trans. Therefore, the former fraction is 1,2-Epoxy-2, 4, 4-trimethylpentane was isomeriz- [VII] and the latter is [VIII]. ed in the presence of ethanol9). [IV] was ob- cis-2,4, 4-Trimethyl-2-pentene-1-ol[V] tained by purification of the crude alcohol (b. p. Ester [VII] was reduced with LiAlH4 followed Bulletinof The Japan Petroleum Institute Isooctenyl Alcohols from Diisobutylene via Chlorination 163 by hydrolysis. The crude product (yield 66.3%) 2.3.7 3-Chloro-2, 4,4-trimethyl-1-pentene was purified by fractional distillation. B.p. [XIII] 172.5℃; d204 0.8539; n20D 1.4518; 3, 5-dinitroben- Chloride [XIII] was obtained from alcohol [III] zoate m. p. 182.1℃. in the same manner used in the preparation of trans-2,4, 4-Trimethyl-2-pentene-1-ol [VI] chloride [X]. In this reaction, chloride [XII] Alcohol [VI] was synthesized from ester [VIII] was formed as a by-product by allyl rearrange- in a similar manner as alcohol [V] (yield 49.2%). ment11),12). Chloride [XIII] was separated from B. p. 178.1℃; d204 0.8529; n20D 1.4505; 3, 5- [XII] by preparative gas chromatography. dinitrobenzoate m. p. 203.1℃. 2.4 Procedure for Hydrolysis of Monochlo- 2.3.4 1-Chloro-2-neopentyl-2-propene [X] ride To the mixture of 9.64g (0.075mol) of al- Prescribed amounts of alkali, solvent and water cohol [IV] and 14.19g (0.077mol) of tri-n- were placed in a reaction vessel and heated to a butylamine in 110ml of ethyl ether, 9.55g (0.08 given temperature while stirring; then mono- mol) of thionyl chloride was added slowly under chloride which was kept at this temperature was vigorous stirring at -10～0℃. The reaction charged to the vessel, and the reaction was started.