LIQUID ACETYLENE Ethynylation Studies and the Formation of Transition Metal Complexes R .
J .
TEDESCHI
A N D
G.
1. M O O R E
Airco Chemicals and Plastics, P . 0. Box 100, Middlesex, N . J . 08846 The base-catalyzed ethynylation of acetone to 3-methyl-1 -butyn-3-ol in excess liquid acetylene, alone or in the presence of catalytic amounts of ammonia, is reported. The use of the liquefied gas is evaluated in terms of various ethynylation variables and starting materials. Secondary amines undergo ethynylation readily to yield propargyl alkylamines at lower temperature and in higher purity than previously reported. Transition metal complexes of nickel, copper, molybdenum, and palladium compounds were readily formed by reaction with excess liquid acetylene.
EARLIER work
has shown that liquid acetylene can be handled safely in a properly designed pressure system (Tedeschi et al., 1968) and that the liquefied gas can be effectively used in the formation of alkali metal acetylides and sodium propiolate (H-C = C-C02Na) (Tedeschi and Moore, 1969). A.dditiona1 studies reported in this paper deal with the catalytic ethynylation of carbonyl compounds and amines and the formation of transition metal complexes in excess liquid acetylene. Catalytic Ethynylationi of Carbonyl Compounds
The base-catalyzed ethynylation of aldehydes and ketones to ethynyl carkiinols in donor solvents has been shown (Tedeschi, 1965, Tedeschi et al., 1963a,b) to involve the intermediate formation of complexes comprising (A) acetylene-solvent, (B) acetylene-alkali metal hydroxide, and (C) ethynyl icarbinol-alkali metal hydroxide. Complexes of B and C have been isolated and studied (Tedeschi et al., 1963a,b), while solubility studies at atmospheric and eleva1,ed pressures (Tedeschi et al., 1968) confirm the existence of A. The key species in the catalytic ethynylation of acetone is the base adduct of 3-methyl1-butyn-3-01 (MB-KOH complex).
I (CH:),-C-C
I
= C H I KOH
OH MB-KOH complex
(C)
This complex exchanges with excess acetylene under pressure to form the precursor KOH-acetylene complex, prior to its reaction with acetone (Tedeschi, 1965). One mole of MB-KOH coimplex results in the formation of 9 to 10 moles of MB at a conversion efficiency of 7570 (based on acetone). I n contrast, the catalytic effect is much less in organic solvents such as ethers, acetals, or
amines (Tedeschi et al., 1963a,b). The postulated reaction sequence is:
MB-KOH
+ C,H?'--MB + [ C H = C H ] KOH
Since an excess of both ammonia and acetylene increases the catalytic efficiency of ethynylation, it was of interest to determine the effects of only excess liquid acetylene or its use with small to catalytic amounts of ammonia. Liquid ammonia is a cocatalyst for ethynylation and any usage (moles) less than that of acetylene or the carbonyl component can be regarded as catalytic. Previous results (Tedeschi and Moore, 1969) with alkali metal acetylides and sodium propiolate have shown that only catalytic amounts of ammonia or trimethylamine are required to activate acetylene. Table I illustrates the importance of a cocatalyst such as ammonia, and its relationship to acetylene, acetone, and potassium hydroxide. I n the absence of ammonia (experiments 4 and 5) the conversion to 3-methyl-1-butyn3-01 (MB) averages only 15 to 2570 and the reaction is not catalytic with respect to KOH. Also, an approximate two- to fourfold excess of liquid acetylene over acetone fails to activate the reaction markedly. I n contrast (experiment l ) ,the use of a catalytic amount of ammonia with respect to acetylene (0.6 mole of NH3 per mole of C2H2) converts 87% of the acetone to M B with a catalytic conversion of 600% (6 moles of M B per mole of KOH). Experiments I, 2 , and 3 also show that conversions are optimum when the concentration of ammonia is slightly greater than that of acetone. A definite mass action effect due to increasing the concentration of liquid acetylene is shown by comparing experiments 1 and 2 (presence of "3) and 4 and 5 I n the absence of KOH (experiment (absence of "3). 7) liquid acetylene and ammonia fail to yield any MB, showing that a solvent complex by itself, of the type is incapable of effecting ethynylation. H-C = CH . . . "3, Ind. Eng. Chem. Prod. Res. Develop., Vol. 9, No. 1, March 1970
83
Table 1. Formation of Methylbutynol in liquid Acetylene %. Co nvers ion"
Moles E.@. 1 2 3 4 5 6 7
Liquid C,H, 0.37 0.20 0.75 0.31 0.37 0.40 0.37
Reaction Temp.,
KOH
Acetone
NH3
"C
Time Hr
0.025 0.025 0.021 0.025 0.05
0.15 0.15 0.25 0.157 0.10 0.10 0.10
0.22 0.22 0.10
30-35 30-35 22-36 19-21 -8-30 20 -28-26
1% 1% 2 2 2 2 3%
...
...
... ... 0.13
Psig 440-515 460-540 480-570 530-560 308-850 420 268-485
Based on Acetone KOP 87 61 48 15 25 0 0
O/c Acetone Recovered
5 16 32 64 19 74 80
600 366 573 92 50 0 0
Conversion based on KOH defined as catalytic effect, moles of methyl butynol produced per mole of KOH. ' Used uisual zhaker reactor (Tedeschi et al., 1968) in all runs except 3, in which a stirred autoclave was used. Used 0.010 mole of MB-KOH complex as catalyst and 5 cc (0.052 mole) of methyl butynol as solvent for complex.
Likewise, the key catalyst for ethynylation, the MB-KOH complex, fails to effect any conversion to M B (experiment 6) in the absence of ammonia. This species is always formed in situ in any ethynylation involving alkali hydroxides, with the exception of lithium hydroxide (Tedeschi et al., 1963a,b, 1965). The latter, although capable of forming a LiOH-C2H2 complex in liquid acetylene (Tedeschi et al., 1968), does not react with acetone, even in liquid ammonia, to form the prerequisite MB-LiOH adduct. The ethynylation of formaldehyde t o propargyl alcohol in the catalytic ammonia-KOH system fails to yield the desired product (Tedeschi et al., 1963a,b). The major products are hexamethylenetetramine and Cannizzaro and aldol products. Likewise, the use of paraformaldehyde, formalin (37%), or methyl Formocel (46%;0),respectively, in excess liquid acetylene with catalysts such as KOH, NaOH, or copper acetylide on carbon failed t o yield propargyl alcohol. The catalytic ethynylation of acetaldehyde and ethylene oxide in a two- to threefold excess of liquid acetylene, using in successive runs catalytic amounts of Na, KOH, or NaOH together with catalytic amounts of ammonia or trimethylamine, also failed to yield the desired butynol derivatives. In contrast, acetaldehyde can be ethynylated catalytically (KOH or NaOH) in excess liquid ammonia, using excess acetylene under pressure in over 50% conversion (Tedeschi et al., 1963a,b). Similar results can be obtained in liquid ammonia with ethylene oxide, if a stoichiometric amount of sodium or sodium acetylide (made in situ) is employed (Henne, 1945). These results indicate that excess liquid acetylene by itself is a poor ethynylation medium, and apparently works best with ketones. I t is, however, easily activated by minor amounts of polar materials such as ammonia or low molecular weight amines. Although work has not yet been extended to higher aldehydes and ketones, it is believed that ethynylation would be successful, particularly when larger amounts of acetylene and cocatalyst 3"( or low molecular weight amines) are used.
catalysts, while acetylene requires copper acetylide catalysis. Recently, an improved method utilizing cupric salts, particularly the chloride, has been described (Moore and Vitcha, 1966). Typically, diethylamine, paraformaldehyde, and gaseous acetylene react in hexane using cupric chloride as catalyst a t 40" to 60°C under pressure t o give conversions to propargyl diethylamine (D) and to bis-(diethylamino)butyne (E) of 80 and 8%, respectively.
Catalytic Ethynylation
Transition Metal Complexes
Secondary Amines to Propargylie Alkyl Amines. The reaction of acetylene and substituted acetylenes with aldehydes and secondary amines to yield propargyl amines is well known (Raphael, 1955). Negatively substituted acetylenes (Coffman, 1935; Mannich, 1933), react readily without
Table I1 shows that various transition metal compounds interact readily with excess liquid acetylene under mild conditions to form complexes. By reaction of a measured volume of acetylene with the respective compound in a stirred autoclave and subsequently measurement of the
84
Ind. Eng. Chem. Prod. Res. Develop., Vol. 9, No. 1, March 1970
(C,H,),NH
+ (HCH0)x + H C = C H
-3
(C2Hj)ZNCHzC CH + H20 (D) (CZHj)2NCH?CE C H + (HCH0)x + HN(C2Hs)Z(C2Hs)rNCHrC E CCHzN(C?Hs)r+ HrO (E) This reaction, however, requires slow, carefully controlled addition of the amine to the reaction mixture. Too rapid an addition leads t o by-products (methylene bisdiethylamine) as well as higher yields of the secondary product, diaminobutyne. No significant reaction takes place a t 20" to 25°C (Moore, 1959; Salvador and Simon, 1966). I t was of interest t o determine if the above process could be further improved by the mass action effect of liquid acetylene. The liquefied gas in the absence of hexane (1.0 mole of C2H2,0.20 mole of paraformaldehyde, 0.20 mole of methylamine, 0.0074 mole of cupric chloride) a t 12" to 24" gave a 58% conversion t o D. Although rapid addition of amine was employed, the reaction was free of by-products. Activation by liquid acetylene was also indicated by the lower reaction temperature that could be used, which in turn may be responsible for the lack of by-products. Similar results (44% conversion) were also obtained when diethylamine, hexane (7.5 ml), and liquid acetylene were employed under identical conditions. The higher conversion in the first experiment is probably due to the use of the more polar dimethylamine and the lack of the nonpolar diluent, hexane. Since no by-products were formed, yields can be considered essentially quantitative.
Table II. Acetylene Transition Metal Complexes
Expt.
No.
Compound
1
NiBr, NiBr, Ni(CKj, CU>Cl,* Mo(COj6 PdCL
2 3 4 5 6
Mole Compound C2H2 0.044 0.043 0.10 0.10 0.05 0.05
0.90 0.90 0.90 0.90 0.90 0.90
O
C
26-33 24-28 20-30 24-31 24-28 22-32
Time, Hr
C2H2, ABS. Mole
7; Conu.
Pressure, Psig
to Complex
Co mp lexn Formed
670-730 630-710 590-700 630-720 630-710 590-710
3.5 4.5 3.5 3.0 5.0 3.0
0.078 0.123 0.010 0.104 0.0258 0.0490
89 95 10 89 52 98
NiBr,. 2C,Hi NiBrs. 3CrH, Ni(CNji. C L H ? Cu>CLHrOi Mo(CO),.C>H, PdCli .C>H>
'Isolated complexes showed no tendency to decompose exothermically, ignite, or explode on exposure to air. They were (IS a safety precaution, stored under nitrogen uith loose bottle caps. Unusual result obtained with CulC12 due to formation of a stable black copper-acetylene adduct, i n xhich no volume change>LLIS noted.
volume of unreacted acetylene, the approximate composition of a given complex could be readily determined (exception, cuprous chloride, experiment 4). The NiBrl complex gradually lost acetylene on standing a t atmospheric pressure in an acetylene atmosphere. During 2 % hours 22% of the original complex decomposed. Complexes of the above type could possibly be precursor species in the carbonylation (CO) of acetylene to acrylate esters in the presence of NiBrl and alcohol. This route has been shown to involve the intermediate formation of nickel carbonyl (N i[CO].J and possibly unstable nickel bromide-carbon monoxide complexes (Hieber, 1939) formed a t higher temperatures (150" to 180") and pressures (200 atm.). The low conversion to a Xi(CN), complex (experiment 3) is in accord with the low efficiency of this compound as a catalyst for cyclooctatetraene (COT) formation (Copenhaver and Bigelow, 1949; Tedeschi and McMahon, 1959). A pi complex between the Ni(I1) ion and four acetylene molecules has been postulated as the active intermediate in this reaction. The absence of COT formation in the liquid acetylene experiments (Table 11) using both Ni:i(CN)rand NiBr2 as catalysts, supports the belief that a 1 to 4 complex is required but not readily formed. The high conversion to a PdC12 complex (experiment 6) is in agreement with the strong chemisorption of substituted acetylenes on palladium and platinum catalysts (Raphael, 1955) and the formation of Pt(I1) complexes of acetylenic glycols (Chatt et al., 1961, 1963). Mo(CO)6 is believed to interact with acetylene by H-bonding rather than by direct replacement of CO, as is typical for transition metal-CO complexes. Replacement of CO would have resulted in the displacement of an equal volume of gas, giving a zero volume change for acetylene absorbed. An alternate structure for the complex would involve 2 molecules of M O ( C O )hydrogen-bonded ~ (via CO) with acetylH~, ene to yield a 2 to 1 complex, [ M O ( C O ) ~ ] ~ . Cin~ quantitative yield. The reaction of anhydrous cuprous chloride with excess liquid acetylene, followed by treatment of the reaction product with water prior to isolation (to avoid possible ignition of copper acetylide), yielded a black copperacetylene adduct. No volume change was noted after venting the autoclave through a calibrated gas meter. The isolated black adduct readily dissolved in 10% HC1 with the rapid evolution of acetylene. Both elemental and acetylene analyses supported the empirical formula CuiC,HrOr. A possible precursor for the black adduct is complex (F).
The failure to observe an acetylene volume change is explainable by the possible evolution of an equal amount of hydrogen, which in turn results from the oxidation of Cu(1) t o Cu(I1). Evolved HC1 gas due to the hydrolysis of copper chloride-acetylene complexes would be absorbed in the hydrolysis water and the wet-test meter used, again resulting in no volume change. Other routes involving the formation of such products as copper acetylide and vinyl chloride (Cu2C12-C2H2 reaction to liberate HC1) or ethylene (by disproportionation) are ruled out, since a volume change would be noted. Experimental
Apparatus. A reaction system for safely liquefying and handling acetylene has been described (Tedeschi et al., 1968). The reactors used in the following experiments were either a 125-cc stirred autoclave equipped with jacketed walls through which a heat exchange fluid (methanol) was circulated to control the reactor temperature or a sight-glass reactor suspended in a bath for temperature control and gently rocked back and forth to agitate the reaction mixtures contained therein. Acetylene was measured to either autoclave (usually at -30" to 0°C) from a calibrated buret after assembling and pressure-testing the equipment. Other materials (gases, liquefied gases, liquids) were introduced via standard techniques from pressure burets also calibrated and equipped with needle valves allowing accurate control of addition rates and quantity of materials added. A pressure drop of 100 psig from the calibrated buret was equal to 0.90 mole of acetylene (24.1 liters) at 19°C and 750 mm and is the basis for introducing accurate amounts of acetylene. Volumes of liquefied acetylene reported herein are based on known density values and are only for the convenience of the reader. Solids, slurries, etc., were charged into either autoclave before assembling. I n all cases the autoclave and the entire pressure system were purged with N 2 and dried thoroughly before each run. The heating-cooling system has been described (Tedeschi et a1., 1968). Preparation of 3-Methyl-1-butyn-3-01(MB) (Table I, Expt. 3). Potassium hydroxide powder (1.18 grams, 0.021 mole) was placed in the stirred autoclave. At -40°C acetylene (39 ml, 0.75 mole) was condensed in the autoclave, followed by warming to 0" and addition of liquid ammonia (3.8 ml, 0.10 mole). After warming the mixture slowly to 25" C, Ind. Eng. Chem. Prod. Res. Develop., Vol. 9, No. 1, March 1970
85
acetone (18.4 ml, 0.25 mole) was added during 10 minutes. The temperature was increased to 35°C and the mixture was stirred 2 hours. Diisopropyl ether (35 ml) was added and the gases were bled off. Liquid C 0 2 (5 ml) was added to neutralize the MB-KOH complex. Removal of K H C 0 3 by filtration left a diisopropyl ether solution containing 10.1 grams of M B (48% yield based on acetone, 573% based on KOH) and 4.6 grams of recovered acetone (31.5%). T h e reactions shown in Table I were carried out in a similar manner using the sight-glass reactor instead of the stirred autoclave. Reaction of Liquid Acetylene with Diethylamine and Paraformaldehyde. Paraformaldehyde (6.3 grams, 0.2 mole of HCHO), cupric chloride (1.0 gram), and hexane (7.5 ml) were placed in the stirred autoclave. At -34" to -20°C acetylene (50 ml, 1.0 mole) was liquefied into the autoclave. Over a temperature range of 0" to 20°, diethylamine (14.6 grams, 0.2 mole) was added continuously during 1% hours, followed by stirring another 2 hours a t 25°C. The pressure ranged from 380 t o 540 psig. With the aid of more hexane, the mixture was removed from the autoclave and filtered. A 43.5% conversion of diethylamine or paraformaldehyde to propargyl diethylamine was obtained. Reaction of Liquid Acetylene with Dimethylamine and Paraformaldehyde. The previous procedure was repeated using dimethylamine (9.0 grams, 0.2 mole) instead of diethylamine. No hexane was added to the starting mixture in this run. At the end of the reaction, the mixture was removed from the autoclave with hexane and filtered. A 58.2% conversion'of dimethylamine or paraformaldehyde to propargyl dimethylamine was obtained. Reaction of Nickel Bromide with Liquid Acetylene. Nickel bromide (85%, 10.8 grams, 0.043 mole) and liquid acetylene (47 mi, 0.90 mole) were stirred 3.5 hours a t 24' to 33'C and 670 t o 730 psig. At the end of this time 22.20 liters of acetylene were vented (p, 751 mm; t , 19OC) out of a total of 24.10 liters used initially. Thus, 1.90 liters (0.078 mole) of acetylene remained complexed with 0.043 mole of nickel bromide, an 89% conversion to NiBrn .2C2H2. T h e above procedure was repeated, except that stirring was carried out for 4.5 hours a t 24-28°C and 630 t o 710 psig. At the end of this time, 21.10 liters of acetylene were vented (p, 750 mm; t , 19'C) out of a possible 24.10 liters, leaving 3.00 liters (0.12 mole) of acetylene complexed with the nickel bromide. This calculated as a 95% conversion to NiBr2.3CZH2. However, upon standing acetylene slowly evolved from the complex over a period of 140 minutes, amounting to another 0.61 liter, or 20% of the total acetylene initially complexed with the nickel bromide. Reaction of Nickel Cyanide and Liquid Acetylene. Anhydrous nickel cyanide (11.1 grams, 0.10 mole) and liquid acetylene (47 ml, 0.90 mole) were stirred 3.5 hours a t 20" to 30°C and 590 to 700 psig. At the end of this time 23.85 liters of acetylene were vented (p, 751 mm; t , 19°C out of a total of 24.10 liters used initially. Thus, 0.25 liter of acetylene (0.010 mole) remained complexed with 0.10 mole of nickel cyanide, corresponding to a 10% conversion to a Ni(CN)2-C2H2complex. Reaction of Cuprous Chloride and Liquid Acetylene. Cuprous chloride (9.9 grams, 0.10 mole of Cu2C12) and liquid acetylene (52 ml, 1.0 mole) were stirred 3 hours a t 25" to 30°C and 630 to 720 psig. At the end of this 86
Ind. Eng. Chem. Prod. Res. Develop., Vol. 9, No. 1, March 1970
time 24.00 liters of gas were vented through a wet-test meter out of an initial volume of 23.80 liters of C2H2 used (p, 756 mm; t. 15" C). A black, brittle solid remained in the autoclave, which after washing with water and vacuum-drying weighed 16.5 grams. A sample of the material completely dissolved in concentrated HCl with evolution of acetylene. The following analysis was obtained: carbon, 9.4%; hydrogen, 0.93%; copper, 71.6%; chlorine, 2.570; acetylene, 16.4%; water, 2.1%; oxygen, 10.1%. Based on this analysis, the copper compound corresponded most nearly to Cu2C2H202.The adduct stored under water was stable to prolonged storage a t ambient temperature. Reaction of Molybdenum Hexacarbonyl with Liquid Acetylene. Molybdenum hexacarbonyl (13.2 grams, 0.05 mole) and liquid acetylene (47 ml, 0.90 mole) were stirred 5 hours a t 23" to 33°C and 620 to 735 psig. At the end of this time 23.38 liters of acetylene were vented (p, 748 mm; t , 1S.C) from the reactor out of a total of 24.00 liters initially used, leaving 0.63 liter (0.026 mole) of acetylene complexed with the M O ( C O ) ~The . white solid isolated from the autoclave weighed 13.7 grams after filtration and drying (theoretical yield, 13.9 grams). A 51% conversion calculated as M o ( C O ) ~ . C ~was H ~obtained based on the acetylene (0.026 mole) that remained complexed with the Mo(C0)e. Reaction of Palladium Chloride with Liquid Acetylene. Palladium chloride (PdC12) (8.9 grams, 0.050 mole) and liquid acetylene (47.7 ml, 0.91 mole) were stirred 3 hours a t 22" to 32" and 590 to 710 psig. At the end of this time, 23.29 liters of acetylene were vented (p, 741 mm; t , 18.C) out of a volume of 24.50 liters leaving 1.21 liters (0.049 mole) of acetylene complexed with the palladium chloride. A 98% conversion to PdC12.C2H2was obtained. Sum ma ry
Liquid acetylene, when used under pressure below its critical temperature (35" C), as reactant and solvent, in the presence of small amounts of polar cocatalysts can readily effect such reactions as metallation, ethynylation, and complex formation. Typical cocatalysts are ammonia and trimethylamine. Liquid acetylene in the absence of a cocatalyst is less effective. The base-catalyzed ethynylation of acetone to 3-methyl1-butyn-3-01in liquid acetylene has been studied in terms of various ethynylation variables. The data are believed to be applicable to other ketone and aldehyde starting materials, and represent a new, novel process for alkynols. Secondary amines can also be readily ethynylated to propargyl alkylamines under mild conditions. Transition metal compounds likewise interact readily with liquid acetylene to form complexes. Liquid acetylene in a properly designed reaction system can be handled safely to produce a variety of acetylenic compounds. No explosions or exothermic decompositions were noted a t any time during this work. Literature Cited
Chatt, J., Guy, R. G., Duncanson, L. A., Thompson, D. T., J . Chem. SOC.1961, 827; 1963, 5170. Coffman, D. D., J . A m . Chem. SOC.57, 1978 (1935). Copenhaver, J. W., Bigelow, M. H., "Acetylene and Carbon Monoxide Chemistry," pp. 189-90, 246-65, Reinhold, New York, 1949. Henne, A. L., Greenlee, K. W., J . A m . Chem. SOC.67, 484 (1945).
Hieber, W., 2 . Anorg. Chem. 243, 145-63 (1939). McKennis, A. C., Ind. Eng. Chem. 47, 850 (1955). Mannich, C., Chang, F . T., Ber. 66, 418 (1933). Moore, G. L., Central Research Laboratories, Air Reduction Co., Murray Hill, N. J., unpublished work, 1959. Moore, G. L., Vitcha, J. F., U. S. Patents 3,268,524 (Aug. 23, 1966); 3,268,583 (Aug. 23, 1966). Raphael, R . A., “Acetylenic Compounds in Organic Synthesis,” pp. 21-5, 62-3, Academic Press, New York, 1955. Salvador, R. L., Simon, D., Can. J . Chem. 44, 2750 (1966). Tedeschi, R . J., J . Org Chem. 30, 3045 (1965). Tedeschi, R. J., Casey, A. W., Clark, G. S., Jr., Huckel, R. W., Kindley, L. M., Russell, J. P., J . Org. Chem. 28, 1740 (1963a).
Tedeschi, R. J., Clark, G. S., Moore, G. L., Halfin, A,, Improta, J., Ind. Eng. Chem. Process Design Develop. 7, 303 (1968). Tedeschi, R. J., McMahon, H. C., Central Research Laboratories, Air Reduction Co., Murray Hill, N . J., unpublished work, 1959. Tedeschi, R. J., Moore, G. L., J . Org. Chem. 34, 435 (1969). Tedeschi, R . J., Wilson, M. F., Scanlan, J., Pawlak, M., Cunicella, V., J . Org. Chem. 28, 2480 (1963b).
RECEIVED for review May 13, 1969 ACCEPTED October 23, 1969
LIQUID-PHASE OXIDATION OF WITH SELENIUM DIOXIDE K H A N
A.
J A V A I D ,
NOBORU
SONODA,
AND SHIGERU
TSUTSUMI
Deparlment o f ( ’hemitul Technolog), Facult) of Engineering, Osaka Uniuersitj, Yamadakami,Suita-shi Osaka, Japan
The liquid-phase oxidation of 1,3-butadiene with selenium dioxide in acetic acid solution at 1 10°C. using catalytic amounts of concentrated sulfuric acid in a glass autoclave for 8 hours produced 1,2-diacetoxy-3-butene, 1 -hydroxy-2-acetoxy3-butene, 1,4-diacetoxy-2-butene, 1 -hydroxy-4-acetoxy-2-butene, 3,4-diacetoxyThe tetrtrhydroselenophene, and 3-hydroxy-4-acetoxytetrahydroselenophene. orgcinoselenium compounds were chosen as the reduced state of the oxidant instead of metallic selenium. The known and new products were characterized by infrared, NMR, and mass spectra, and GLC. The effects of water percentage, protlon concentration, butadiene-selenium dioxide molar ratio, reaction time, and reaction temperature were studied to establish optimum conditions for the best yielcls and product distribution. Product yields based on selenium dioxide consumed exceeded 100%.
SEL~NIUM dioxide is often an attractive reagent for the oxidation of’ olefins because of the unique characteristics of the reaction that produce an allylic derivative depending on the solvent used. Elemental selenium is often found in the reduced state of the oxidant. A survey of the literature indicates that in many cases the oxidation product isolated must result from an allylic rearrangement. Olson (1966) and Javaicl et u1. (1969) reported that addition across the double bond takes place in olefins such as ethylene, styrene, and norbornene, where allylic rearrangement is not possible. ‘On the other hand, relatively less attention has been paid to oxidation of conjugated olefins with selenium dioxide. Backer and Strating (1934) isolated a series of selenium dioxide adducts with various substituted butadienes. These were formulated as cyclic selenones.
I
This type of structure was reinvestigated by Mock and McCausland (1968) and declared incorrect. Instead. the following new structure was proposed:
The corresponding adduct of 1,3-butadiene could not be isolated because it was unstable, and it was found that R in I should be a t least one alkyl or aryl group to have a stable adduct (Backer and Strating, 1934). Here we report the oxidation of butadiene in acetic acid solution, with a detailed study of different variables. A new organoselenium compound has been characterized. Experimental Apparatus
All reactions were conducted in a 250-ml. graduated glass autoclave which can be operated up to a pressure of 15 kg. per sq. cm. and fitted with a mechanically operated stainless steel stirrer. Infrared spectra were taken Ind. Eng. Chern. Prod. Res. Develop., Vol. 9, No. 1, March 1970
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