Bartók, Mihály

Molnár, Árpád

Notheisz, Ferenc

English

Bartók Mihály

Molnár Árpád

Notheisz Ferenc

University of Szeged

CHEMICAL TRANSFORMATIONS OF DIOLS AND CYCLIC ETHERS. XXXV* Dehydration of Diols on Copper Catalysts By M. BARTÓK, Á. MOLNÁR and F. NOTHEISZ Institute of Organic Chemistry, Attila József University, Szeged (Received June 23, 1972) The paper deals with the dehydration of certain di-primary and primary-secondary diols (ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,4-pentane-diol, 1,5-pentanedioI and 1,6-hexanediol) on the action of copper catalysts. The rates of dehydra-tion of the 1,3-, 1,4-, 1,5- and 1,6-diols are significantly higher than those of the 1,2-diols. Under the experimental conditions used, the 1,3-diols are dehydrated to oxo compounds containing the same number of carbon atoms, and the 1,4-, 1,5- and 1,6-diols are dehydrated to cyclic ethers. In this paper an account is given of the results obtained in a study of the trans-formations of diols on copper catalysts. The dehydration of certain 1,3- and 1,4-diols on the action of metal catalysts was reported earlier [i—6]. The present work deals with the dehydration of some 1,2-, 1,5- and 1,6-diols in the presence of Cu/Al and Cu/SiOa catalysts ; the main aim of this work was to study the regularities of the copper-catalyzed dehydration of the diols under the same experimental con-ditions, as a function of the relative positions of the two hydroxy groups. To begin with, the more important regularities established in connection with the dehydration of diols are summarized below on the basis of the literature data. In the presence of various dehydrating agents, 1,2-diols in either liquid or gas phase are converted (with accompanying rearrangement) mainly to oxo com-pounds [7, 8]: Since the discovery of the reaction [9, 10], a considerable amount of experimental work by various research groups has shown conclusively that the above process is a widespread reaction of general validity for vicinal diols, i.e. it is one of their characteristic reactions. This finding, which today requires certain amendments, is to be found in various textbooks, reference-books and monographs [7, 11—15, -C—C— - h „ o — C — C — OH OH o * Part XXXIV: F. Notheisz, M. Bartók, V. Remport: Acta Phys. et Chem. Szeged 18, 197 (1972). 208 M . B A R T Ô K , Â . M O L N Â R A N D F . N O T H E I S Z etc.]. Our results to date show that the study of the exactness of the above regularity and its further generalization has proved to be a useful research programme. Under certain conditions 1,3-diols, too, are converted to oxo compounds with the same number of carbon atoms [1, 6]. Although similar observations were also made at the turn of the century [16,17], no special attentiçn was devoted to this theoretically important question. 1,4-, 1,5- and 1,6-diols are dehydrated to cyclic ethers, dienes and unsaturated alcohols [7, 18, 19], while on copper catalysts they are converted to lactones [20]: ^ C ^ C H — ( C H 2 ) — C — — ^ C ^ C H — ( C H 2 ) — C H = C / / ^ 7 1 - 1 | - » 2 ° y ' V 71 — 2 O H ( C H 2 ) „ V N / / \ / \ O - h , o cu ( C H 2 ) „ — 2 H 2 0 \ / \ c c = o / \ / o n = 2, 3,4 Of course, the extent of the individual reactions is significantly affected, and in some cases even determined, by the number of methylene groups n, by the order of the carbon atoms bonded to the hydroxy groups, and by the nature of the ca-talyst. Of the diols, the dehydrations of mainly 1,4-butanediol, 1,3-butanediol and 3-methyl-l,3-butanediol have been dealt with, and the results are collected in some monographs [7, 18, 21]. The aim of the investigations was the preparation of 1,3-butadiene and isoprene. The most suitable catalysts for these purposes proved to be phosphoric acid and various inorganic phosphates. The dehydration of diols on metal catalysts has been dealt with in only one or two publications. Of these, mention should be made of the paper by PINES and STEINGASZNER [22] describing the dehydration of 1,4-butanediol and 1,5-pentanedioi accompanied by the forma-tion of cyclic ethers. In our study of the dehydration of 1,3- and 1,4-diols on Cu/Al and Cu/SiOa catalysts, it was found that in the case of 1,3-diols three main reactions take place, depending on the structures of the 1,3-diols [3]: the formation of oxo compounds containing the same number of carbon atoms as the diols, 1,2-elimination and fragmentation processes. Under similar experimental conditions 1,4-diols are de-hydrated with the formation of tetrahydrofuran homologues [2]. DIOLS AND CYCLIC ETHERS. XXXV. DEHYDRATATTON OF DIOLS ON COPPER CATALYSTS 2 0 9 In the present paper we report the experimental results of the dehydration, under identical experimental conditions, of the following model compounds1: C H 2 - ( C H 2 ) - C H 2 C H 2 — ( C H 2 ) - C H — C H 3 • -I' I . I I OH OH OH OH /1 = 0 , 1 , 2 , 3 , 4 « = 0 , 1 , 2 The investigations were carried out in the apparatus already described in detail [1], on Cu/Al and Cu/SiOa catalysts between 150 and 300 °C in a continuous system, with a flow-rate of 0.1—1 hr _ 1 . The description of the experimental method and the preparation of the catalysts can also be found in earlier papers [1, 5]. The ex-perimental results can be summarized as follows: Examination, of the conversion with different temperatures showed that the 1,2-glycols are very stable on both catalysts. On a Cu/Al catalyst at 300 °C the propylene glycol conversion was only 34%, whereas the conversions of 1,3-, 1,4- and 1,5-diols attained 100% even at low temperature. Under the experimental conditions used propylen glycol is converted to the fol-lowing products: CH3—CH2—CHO + CH3—CO—CH3 + C H 2 = C H — C H O CH3—CH—CH2 - CH 2 =CH—CH 2 OH + CH3—CH2—CH2OH OH OH CH3—CHOH—CHO + CH3—CO—CH2OH For example, the composition of the product obtained in the experiment at 300°C on a Cu/Al catalyst was: propionaldehyde 7%, allyl alcohol + propyl alcohol 16%, acrolein 37%, acetone 23%. Thus, the amount of the products formed by the elimination of the secondary hydroxyl group (55 %) is significantly larger than the amount of product (acetone) formed by the elimination of the primary hydroxyl group (23%). In addition to the above products, as a consequence of the high temperatures, also various decomposition processes of primary and secondary origin occur. Under experimental conditions (relatively low temperature and higher flow-rates) when the conversion of propylene glycol was only 25%, the formation of 2-hydroxypropionaldehyde could be observed with very high selectivity on the Cu/Al catalyst. Under similar experimental conditions 1,3-propanediol is converted to pro-pionaldehyde, and 1,3-butanediolto methyl ethyl ketone and butyraldehyde [1, 3, 6]. On a Cu/Al catalyst the 1,4-, l-,5- and 1,6-diols are converted to cyclic ethers of corresponding ring size. In the above temperature range, with flow rates of 0.1:—1 h r - 1 , the conversion attains 100%, independently of the structure of the diol. In the case of 1,4- and 1,5-diols the conversion is accompanied by the forma-tion of the tetrahydrofuran and tetrahydropyran homologues, and is selective. In 1 The selected model compounds were commercial products. 2 1 0 M. BARTÓK, Á. MOLNÁR AND F. NOTHEISZ addition to oxa-cycloheptane as main product (ca. 40%) from hexamethylene gly-col the formation of other so far unidentified compounds is also observed : (CH2)n Cu CH, \ CH2—(CH2)„—CH—R 200_3(X)„C OH OH O « = 2 , 3 , 4 ; R = H , CH3 C H — r + H2O In the low-conversion transformation of 1,4-diols, oxy-oxo compounds and other so far unidentified products are also formed; the further study of these may provide useful information for elucidating the mechanism of dehydration of diols on metal catalysts. . Our experimental results therefore indicate that the studied diols are dehydrated on Cu/Al and Cu/SiO, catalysts in accordance with the following scheme: CH2—(CH2)„—CH—R I I OH OH ( R = H , CH3) Cu 200-C —H2O • /1 = 0 n=l no transformation CH3—(CH2)„—C—R + 0 R—(CH2)„—CH2—CHO n = 2, 3,4 (CH2)„ / \ CH2 CH—R \ / o The mechanisms of the observed processes will be dealt with in a later paper. References [1] Bartók, M., B. Kozma: Acta Phys. et Chem. Szeged 9, 116 (1963). [2] Shuykin, N. /., M. Bartók, R. A. Karahanov, V. M. Shostakovskii: Acta Phys. et Chem. Szeged 9, 124 (1963). [3] Bartók, M., L. Zalotai: Acta Phys. et Chem. Szeged 14, 39 (1968). [4] Zalotai, L„ M. Bartók: Acta Phys. et Chem. Szeged 14, 47 (1968). [5] Bartók, M.,B. Prágai: Acta Phys. et Chem. Szeged 18, 50 (1972). [6] Bartók, M„ A. Molnár: Acta Chim. Acad. Sci. Hung, (in press). [7] Winefild, M. E.: Catalysis, Vol. VII. (Ed.: Emmett, P. H.), Reinhold, New York, 1960. [8] Collins, C. J.: Quart. Rev. 14, 357 (1960). [9] Fittig, R.: Ann. 114, 56 (1860). [10] Butlerov, A. M.: Ann. 174, 127 (1874). [11] Ingold, C. K.: Structure and Mechanism in Organic Chemistry (Cornell Univ. Press, Ithaca, New York, 1953). DIOLS AND CYCLIC ETHERS. XXXV. DEHYDRATATION OF DIOLS ON COPPER CATALYSTS 2 1 1 [12] Dartilov, S. N.: Reaktsii i metodi issledovaniya organicheskih soedinenii 4, 159 (1956). [13] Temnikova, Т. I.: Kurs teoreticheskih osnov organicheskoi khimii (GHI, Leningrad, 1959) p. 589. [14] Bruckner, Gy.: Szerves Kémia, Vol. I—1 (Tankönyvkiadó, Budapest, 1961) p. 311. [15] Orehov, A. P.: Vnutrimoleculyarnie peregruppirovki (Nauka, Moscow, 1965). [16] Bauer, F.: Monatshefte 25, 1 (1904). [17] Kadiera, V.: Monatshefte 25, 332 (1904). [18] Reppe, W. et at.; Ann. 596, 1 (1955). [19] Freydlin, L. H., V. Z. Sharf: Dokl. AN SSSR 136, 1108 (1961). [20] Larkin, D. R.: J. Org. Chem. 30, 335 (1965). [21] Glycols, ACS Monograph Ser. No. 114 (Ed.: Curme, G. O., F. Johnston) Reinhold, New York 1952. [22] Pines, H., P. Steingaszner: J. Catalysis 10, 60 (1968). ХИМИЧЕСКИЕ ПРЕВРАЩЕНИЯ ДИОЛОВ И ЦИКЛИЧЕСКИХ ЭФИРОВ. XXXV. ДЕГИДРАТАЦИЯ ДИОЛОВ НА МЕДНЫХ КАТАЛИЗАТОРАХ М. Барток, А. Молнар и Ф. Нотейс Исследована дегидратация некоторых ди-первичных и первично-вторичных диолов. (этиленгликоль, пропиленгликоль, 1,3-пропанциол, 1,3-бутандиол, 1,4-бутандиол, 1,4-пен-тандиол, 1,5-пентандиол, 1,6-гександиол) на медных катализаторах. Скорость дегидратации 1,3-, 1,4-, 1,5- и 1,6-диолов значительно больше скорости дегидратации 1,2-диолов. При исследованных нами экспериментальных условиях 1,3-диолы превращаются в оксосоединения с одинаковым числом углеродных атомов, а 1,4-, 1,5- и 1,6-диолы дегидратируются в соот-ветствующие органические окиси. 

Chemical transformations of diols and cyclic ethers 35. : Dehydration of diols on copper catalysts

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Chemical transformations of diols and cyclic ethers 35. : Dehydration of diols on copper catalysts

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