Ethylidene diacetate acetate

The catalyst components are generally dissolved in methyl acetate which acts as both reactant and solvent. Other solvents may be used and in fact, upon several batch recycles where lower boiling products are distilled off, the solvent is an ethylidene diacetate-acetic acid mixture. Any water introduced in the reaction mixture will be consumed via ester and anhydride hydrolysis, therefore anhydrous conditions are warranted. Typical batch reaction examples are presented in Table 1. There is generally sufficient reactivity when carbon monoxide and hydrogen are present at 200-500 psi. Similar results were obtained from the pilot plant using a continuous stirred tank reactor (CSTR). The reaction can also be run continuously over a supported catalyst with a feed of methyl acetate, methyl iodide, CO, and hydrogen. 

Acetyl chlotide is reduced by vatious organometaUic compounds, eg, LiAlH (18). / fZ-Butyl alcohol lessens the activity of LiAlH to form lithium tti-/-butoxyalumium hydtide [17476-04-9] C22H2gA102Li, which can convert acetyl chlotide to acetaldehyde [75-07-0] (19). Triphenyl tin hydtide also reduces acetyl chlotide (20). Acetyl chlotide in the presence of Pt(II) or Rh(I) complexes, can cleave tetrahydrofuran [109-99-9] C HgO, to form chlorobutyl acetate [13398-04-4] in about 72% yield (21). Although catalytic hydrogenation of acetyl chlotide in the Rosenmund reaction is not very satisfactory, it is catalyticaHy possible to reduce acetic anhydride to ethylidene diacetate [542-10-9] in the presence of acetyl chlotide over palladium complexes (22). Rhodium trichloride, methyl iodide, and ttiphenylphosphine combine into a complex that is active in reducing acetyl chlotide (23). 

Owing to the tendency for ethylidene diacetate to be formed at elevated temperatures, care is taken for the rapid removal of vinyl acetate from the reaction vessel as soon as it is formed (Figure 14.1). 

In 1953 the Celanese Corporation of America introduced a route for the production of vinyl acetate from light petroleum gases. This involved the oxidation of butane which yields such products as acetic acid and acetone. Two derivatives of these products are acetic anhydride and acetaldehyde, which then react together to give ethylidene diacetate (Figure 14.2.)... 

Exposure of the ethylidene diacetate to an aromatic sulphonic acid in the presence of five times its weight of acetic anhydride as diluent at 136°C will yield the following mixture 40% vinyl acetate 28% acetic acid 20% acetic anhydride 4% ethylidene diacetate 8% acetaldehyde. 

Moiseev et al., who proposed initially that ethylidene diacetate was produced from addition of acetic acid to vinyl acetate, later showed this to be impossible from the result of reaction in CH3CO2D, preferring the following mechanism ... 

Water also causes a change in the reaction medium, which may be advantageous. A drawback of the reducing medium in the Eastman process is that in addition to acetic anhydride, the by-product ethylidene diacetate is formed, CH3CH(AcO)2. This can be thermally decomposed to vinyl acetate and acetic acid, or it can be reduced to ethyl acetate, which in the recycle would lead eventually to propionic acid. 

Starting from acetic anhydride, according to Equation 7, vinyl acetate can be obtained via ethylidene diacetate (22). 

By adjusting the C0 H2 ratio, catalytic systems for the reductive carbonylation of methyl acetate can be tuned to the production of acetic anhydride, ethylidene diacetate or acetaldehyde. 

This report describes a process to produce vinyl acetate with high selectivity from exclusively methanol, carbon monoxide, and hydrogen. The simplest scheme for this process involves esterifying acetic acid with methanol, converting the methyl acetate with syn gas directly to ethylidene diacetate and acetic acid, and finally, thermal elimination of acetic acid. Produced acetic acid is recycled. Each step proceeds in high conversion and selectivity. 

The single step conversion of methyl acetate to ethylidene diacetate is catalyzed by either a palladium or rhodium compound, a source of iodide, and a promoter. The mechanism is described as involving the concurrent generation of acetaldehyde and acetic anhydride which subsequently react to form ethylidene diacetate. An alternative to this scheme involves independent generation of acetaldehyde by reductive carbonylation of methanol or methyl acetate, or by acetic anhydride reduction. The acetaldehyde is then reacted with anhydride in a separate step. 

Alternatively, the transformation of methyl acetate to ethylidene diacetate may also be achieved in a multistep process. Either conversion of methyl acetate to acetic anhydride, followed by reduction to ethylidene diacetate plus acetic acid, or production of acetaldehyde directly and subsequent reaction with acetic anhydride to form ethylidene diacetate are successful. This will be examined in greater detail. 

As indicated above, ethylidene diacetate (EDA) is a precursor of vinyl acetate by thermal elimination of acetic acid (equation 3). 

Reductive Carbonylation of Methanol. As discussed earlier, rhodium based catalysts are capable of catalyzing the reductive carbonylation of methyl acetate to ethylidene diacetate ( 1), as well as the carbonylation of methyl acetate to acetic anhydride (16). These reaction proceed only, wjjen, tjie reaction environment... 

Thermal Elimination of Acetic Acid from Ethylidene Diacetate... 

Equally notable is a change in type of by-products when RhCl3 is used as co-catalyst. In Experiments VI-IX both ethylidene diacetate (EDA) and acetic anhydride (AH) are formed as (minor) byproducts. In Experiments I-III not even a trace of these products can be detected and instead alcohols and ethers are co-produced. With RhCls, and in the absence of RUCI3 (Exps. IV, V), EDA and AH are the main reaction products. 

In the 1940 s, in addition to these operations, two other processes became important. Acetic acid was made by reacting methanol with carbon monoxide, and acetic anhydride was being made by the ethylidene diacetate process, which in effect is the dehydration of acetic acid to the anhydride by the use of acetylene. Fermentation ethyl alcohol was converted to acetic acid via acetaldehyde as well as by the direct oxidation of ethyl alcohol. A new operation on the Gulf Coast was also based on acetaldehyde. However, the acetaldehyde is made by the direct oxidation of liquefied petroleum gas. A further process for the production of these materials, in which acetaldehyde is oxidized in one step to a mixture of anhydride and acid, was also begun. 

Ethylene is readily absorbed by solutions of PdCl2 in acetic acid,5,4 but the presence of acetate ions (as NaOAc or LiOAc) is essential for reaction.S34a,b Van Helden et a/.53Sa found that ethylene at 1 atm reacts with Pd(OAc)2 at 70°C to form palladium metal and vinyl acetate (40-50%), together with acetaldehyde, ethylidene diacetate, and acetic acid. The rate of reaction increases considerably in the presence of sodium acetate and the selectivity to vinyl acetate is much higher (80-90%). 

The process takes place in two stages. Firstly acetaldehyde and acetic anhydride form ethylidene diacetate in liquid phase at 120-140 °C with FeCl3 as a catalyst ... 

Even with added iodide salt formation of the inactive [Rh(CO)2l4] can be a problem, since under anhydrous conditions this Rh(III) species cannot be reduced to the active [Rh(CO)2l2] by reaction with water. In the Eastman process, this problem is addressed by addition to the CO gas feed of some H2 which can reduce [Rh(CO)2l4] by the reverse of Equation 8. However, the added H2 does lead to some undesired by-products, particularly ethylidene diacetate (1,1-diacetoxyethane) which probably arises from the reaction of acetic anhydride with acetaldehyde (Equation 19 from hydrogenolysis of a rhodium acetyl) ... 

Acetylation of acetaldehyde to ethylidene diacetate [542-10-9], a precursor of vinyl acetate, has long been known (7), but the condensation of formaldehyde [50-00-0] and acetic acid vapors to furnish acrylic acid [97-10-7] is more recent (30). These reactions consume relatively more energy than other routes for manufacturing vinyl acetate or acrylic acid, and thus are not likely to be further developed. Vapor-phase methanol—methyl acetate oxidation using simultaneous condensation to yield methyl acrylate is still being developed (28). A vanadium—titania phosphate catalyst is employed in that process. 

The ethylidene diacetate formed can be converted to vinylacetate and acetic acid in high yield by passage over a metal oxide catalyst at high temperatures. The net reaction is given in Equation (17). 

For synthesis of ethylidene diacetate, other startmg materials have also been proposed. Hydrogenation of acetic anhydride by a palladium catalyst [3gj or caibonylafion of CH3CH(OCIl3)2 with RhCl3/Ph3P/MeJ (39] are two alternative routes. 

Homogeneous Acetaldehyde and acetic anhydride react in liquid phase in the presence of a catalyst to give ethylidene diacetate, which decomposes to acetic acid and vinyl acetate. 

In some of the studies on the vinyl acetate synthesis from ethylene, high boiling products were reported (9, 10, 24, 25, 26). These included ethylidene diacetate (III), ethylene glycol monoacetate (IV) and ethylene glycol diacetate (V). Little attention has been given to the reactions by which these products are formed. No dioxygenated products have been reported previously when higher olefins have been used. 

Moiseev and Vargaftik (36) have reported that deuterium is not incorporated into either vinyl acetate or ethylidene diacetate (III) when the vinyl acetate synthesis reaction is carried out in deuteroacetic acid. They considered this observation as evidence for a process such as Reaction 4 in which the final carbonium ion (VII) is forming products either by losing a proton or by reacting with acetate to give ethylidene diacetate (III). 

The existence of a free carbonium ion such as VII in a strongly solvating medium is highly improbable. Only if VII could exist in association with the palladium could decomposition to vinyl acetate be expected to occur with a reasonable degree of frequency, in competition with the reaction with acetate to form ethylidene diacetate. Similar results have been reported in the Wacker acetaldehyde synthesis when D2O is used as the solvent (25). Stern (54) has reported results in which 2-deuteropropylene was used as substrate in the reaction. Based on assumed /J-acetoxyalkylpalladium intermediates, on the absence of an appreciable isotope effect in the proton-loss step, and on the product distribution observed, excellent agreement between calculated (71%) and observed (75%) deuterium retention was obtained. Several problems inherent in this study (54) have been discussed in a recent review (I). Hence, considerable additional effort must be expended before a clear-cut decision can be made between a simple / -hydrogen elimination and a palladium-assisted hydride shift in this reaction. 

The next step in the reaction scheme—decomposition of the a-bonded alkylpalladium (XIV or XV)—has caused some controversy. To account for the results of several deuterium-labelling studies (15, 36, 54), a. palladium-assisted hydride transfer reaction (Reaction 4) has been proposed (36, 54). A number of inconsistencies in the studies using 2-deuteropro-pylene as substrate (54) have been discussed (i). In addition, the formation of a free carbonium ion such as VII [as proposed by Moiseev (36)], while accounting well for the formation of ethylidene diacetate, is much less satisfactory in accounting for the production of the unsaturated esters in an acetate-acetic acid medium. A simple elimination of -hydrogen (Reactions 13a and b) could also account for the products formed. While not necessary for the reaction, chloride assistance for proton removal is a possibility and has been postulated previously for a similar reaction (i, 37). 

Formation of 1,1-diacetates—e,g., ethylidene diacetate from ethylene or hexylidene diacetate from hexene—by simple acetate displacement of palladium (Reaction 16) is a much more satisfactory reaction scheme than any previously proposed. On the other hand, accounting for 1,2-diol type products is diflBcult by this scheme, necessitating a reverse hydrogen transfer to form a two-carbon insertion product intermediate. This type... 

The hydrocarbonylation of methyl acetate catalyzed by homogeneous Rh complexes generates 1,1-diacetoxyethane ( ethylidene diacetate ) [61] the formal addition product of acetic anhydride and acetaldehyde. Ethylene diacetate is the predominant by-product of the process. The level of ethylidene diacetate production is directly related to the hydrogen partial pressure in the reactor [62]. 

---