Reaction of Propylene with Formaldehyde*

Reaction of Propylene with Formaldehyde* Kenichi Fukui,** Toshio Takino** and Hisao Kitano** Summary: The reaction of propylene with formaldehyde in acetic acid solution catalyzed by sulfuric acid is studied . The optimum mole ratio of sulfuric acid to formaldehyde is found to be about 0.2 and the favorable range of reaction temperature is 35～50℃ at ordinary pressure . The acetic acid containing 30 vol % of acetic anhydride serves as a suitable solvent. The products are 4-methyl-1, 3-dioxane, 1, 3-butanediol diacetate and 4-acetoxytetrahydropyran, and the former two of these compounds can be converted to pyran derivatives via allylcarbinol acetate. However, the formation of 4-acetoxytetrahydropyran from propylene and formaldehyde by the Prins reaction may be explained by the Baker's mechanism of hyperconjugation of the propylene methyl radical without considering the formation of allylcarbinol acetate. Various reactions of 4-hydroxytetrahydropyran are carried out and its derivatives are prepared, including several new compounds. For the sake of comparison with the reactivity of propylene, some reactions of allyl halides with formaldehyde are also studied and the main products are found to be 4-halomethyl-1, 3-dioxanes. Introduction What is called the Prins reaction, the condensation of olefins and aldehydes, is generally accelerated by catalysts, heat and light. The reaction of propylene with formaldehyde was investigated by some workers, i. e. by Fitzky,1) Baker,2) Hamblet3) and Arundale,4) since 1938. Our previous paper5) has shown that propylene reacted with formaldehyde in acetic acid in the presence of various catalysts, e. g. sulfuric acid, perchloric acid and boron trifluoride, to yield 4-methyl-1, 3-dioxane, 1, 3-butanediol diacetate and 4-acetoxy-tetrahydropyran. In the case of perchloric acid catalyst, 4-methyl- 1, 3-dioxane was obtained in good yields, whereas boron trifluoride and sulfuric acid catalysts favored the formation of 1, 3-butanediol diacetate. catalyzed by sulfuric acid is systematically Recently, the Prins reactions of this type studied to elucidate the reaction conditions to have attracted attention from the point of the obtain good yields of desired products. Addi- utilization of lower olefins and aldehydes from tional experiments are made with regard to petrochemical industry.6) In the present work, the reactions of pyran derivatives. The reac- the reaction of propylene with formaldehyde tions of some allyl halides with formaldehyde * Received November 14 are also studied. , 1960. This work is supported Propylene under atmospheric pressure is financially in part by a grant-in-aid from the Ministry of Education. Japanese Government. bubbled into a suspension of paraformaldehyde ** Department of Fuel Chemistry , Faculty of Engineer- in the mixture of sulfuric and acetic acids ing, Kyoto University, Sakyo-ku, Kyoto. which is kept at 37～42℃. The weight of Volume 3-March 1961. 28 Fukui, Takino and Kitano: Reaction of propylene absorbed is but little changed with However, the formation of allylcarbinol acetate the mole ratio of sulfuric acid to formaldehyde from 1, 3-butanediol diacetate and the con- in the range from 0.16 to 0.48. Practically, densation of allyecarbinol acetate with form- the mole ratio of ca. 0.2 is recommended. aldehyde require a high temperature and is not Although the maximum absorption of propylene usable in the reaction of propylene with form- is effectuated at 50～60℃ under ordinary pres- aldehyde. For instance, the elimination of sure, the reaction should be carried out at 35～ 1, 3-butanediol diacetate (prepared by boiling 4- 50℃ because the tar formation increases at a methyl-1, 3-dioxane with acetic acid-acetic an- higher temperature. hydride mixture in the presence of sulfuric acid) The propylene absorption can be accomplished can be barely made by distillation in the pre- more efficiently in a mixture of acetic acid and sence of p-toluenesulfonic acid. 4-Acetoxy- acetic anhydride than in acetic acid only. The tetrahydropyran is prepared by refluxing the highest yield of the products is obtained in the mixture of allylcarbinol acetate and paraform- mixture of acetic acid containing 30 vol. % aldehyde in acetic acid in the presence of anhydride. In this optimum condition, 4-methyl- sulfuric acid. 1, 3-dioxane, 4-acetoxytetrahydropyran and 1, The experimental facts mentioned above in- 3-butanediol diacetate are formed in the ratio dicate that the formation of pyran derivatives of about 2:5:10. In the case of more than from propylene and formaldehyde may be ex- 50% of the acetic anhydride content in the plained by Baker's mechanism2) involving the solvent, the product is mainly methylene dia- hyperconjugation of methyl radical of propylene. cetate, which is also found to be prepared in good yields from acetic anhydride and paraformaldehyde in the presence of boron trifluoride complexes. Methylene diacetate will not react with propylene under atmospheric pressure, but when utilized as a solvent for the reaction of propylene with formaldehyde, a similar result to the case of acetic acid, was obtained. 4-Acetoxytetrahydropyran is readily hydrol- yzed to lead 4-hydroxytetrahydropyran.2) Pre- paration of 4-hydroxytetrahydropyran without the use of propylene was carried out by the Products, other than pyran derivatives, from condensation of allylcarbinol with formal- Prins reaction of propylene and formaldehyde dehyde7)8) or by the reduction of nyrone-4.9) can also be converted to pyran derivatives 4-Acetoxytetrahydropyran formed by the through a few steps. Hence, the Prins reac- above-mentioned Prins reaction can be derived tion of this kind is considered as an interesting from 1, 3-butanediol diacetate through allyl- means to prepare pyran derivatives. carbinol acetate, since allylcarbinol or its acetate Some new urethans, tetrahydropyrone-4, and was synthesized by the elimination of 1, 3- its derivatives are also prepared from 4-hy- butanediol or its diacetate7)8). droxytetrahydropyran. Allyl fluoride, allyl chloride, allyl bromide, and methallyl chloride instead of propylene were brought into reaction with formaldehyde to obtain 4-halomethyl-1, 3-dioxanes (4-methyl- chloromethyl-1, 3-dioxane in the case of methallyl chloride) as the main products and some high-boiling substances as by-products. Bulletin of The Japan Petroleum Institute Propylene with Formaldehyde 39 3. Separation of the products: Experimental The reaction mixture containing propylene absorbed was cooled, neutralized with aqueous 1. Relation between the amount of propy- sodium carbonate solution, and extracted with lene absorbed and the concentration of sulfuric acid: ether. The ethereal solution was washed with In a flask fitted with a mercury-sealed aqueous sodium chloride, dried with anhydrous mechanical stirrer, thermometer, reflux con- sodium sulfate and fractionally distilled. Re- denser and gas inlet, were placed 19g (0.63 distillations of each fractions gave the results mol.) of 60 mesh powdery paraformaldehyde, shown in Table 3. 100cc of glacial acetic acid and 98% sulfuric acid whose amount was indicated in Table 1. 4. Reaction solvents: Twenty six grams (0.62mol.) of purified propy- The reactions were carried out in the same lene in 4hrs was introduced into the mixture manner as described in 1. utilizing the solvents while stirring and the reaction temperature shown in Table 4. One hundred cc of each sol- was maintained at 37～42℃. The amount of vent and 20g. (0.2mol.) of 98% sulfuric acid were employed. The reaction mixture was separated propylene absorbed was measured by the in- creased weight of the mixture. The results and purified by the same treatment as described obtained are shown in Table 1. in 3. The results obtained are shown in Table 4. Table 1. Relation between the Amount of Propylene 5. Methylene diacetate: Absorbed and the Mole Ratio of Sulfuric Acid to Formaldehyde Although methylene diacetate was prepared from the reaction of acetic anhydride with formaldehyde in the presence of zinc chloride,10) sulfuric acid11) and cation-exchange resin,12) the yields were not so high. In the present work, boron trifluoride complex was used as a catalyst by the following procedure to obtain the product in good yields. In a three-necked flask fitted with a stirrer, reflux condenser and thermometer, 140g (4.67mol.) of paraformaldehyde, 840cc of acetic anhydride and 3.5cc of boron trifluoride etherate were placed and gently heated while stirring, until the temperature reached 130℃ and the mixture 2. Relation between the amount of propy- was kept at this temperature for 30 minutes lene absorbed and the reaction temperature: for reaction. After the reaction mixture was The reactions were carried out in the same cooled, the mixture was poured into water manner as described in 1. In this experiment and extracted with ether. The ethereal solu- 20g of 98% sulfuric acid was employed as a tion was dried over anhydrous sodium sulfate catalyst and 26g of purified propylene was and distilled to give 435g (71% yield) of introduced in 2hrs. The amount of propylene methylene diacetate b. p. 75～77.5℃/22mmHg, absorbed in the experiments at various tem- n20D 1.4047 (Ref.12)13) b. p. 62～65℃/11～12mm peratures are shown in Table 2. Hg, n20D1.4025). Although methylene diacetate hardly reacts with propylene in the presence of sulfuric acid Table 2. Relation between the Amount of Propylene catalyst at ordinary pressure, it was used as one Absorbed and the Reaction Temperature. of the solvents, in place of acetic acid, in the reaction of propylene with formaldehyde to afford a result similar to run No. 1 in Table 4. 6. 1, 3-Butanediol diacetate: The fraction III described in 3. consisted of 1, 3-butanediol diacetate. This compound can also be prepared from 4-methyl-1, 3-dioxane of the fraction I of 3. In a flask equipped with a reflux condenser Volume 3-March 1961 .

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