Ethylidene diacetate

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. 

Up to 25% by weight of the product is ethylidene diacetate. The diacetate can be detected by gas chromatographic analysis using a column of the diglyceride of 6,6,6-trifluorohexanoic acid on firebrick at 120°.10 The checkers obtained yields ranging from 24% in a 0.75-scale experiment to 47% on a three-fold increase in scale. 

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. 

ETHYLIDENE DIACETATE 150.2951 -9.1567E+03 -4.8925E+01 1.0422E-09 1.3981E-05 292 635... 

In the carbonylation of MeOAc to AC2O, little or no reaction corresponding to the vater gas shift takes place. Indeed it may be advantageous to feed small amounts of H2 to the process to increase catalyst activity [5]. This is also associated with the formation of ethylidene diacetate, CH3CH(OAc)2, (EDA) (Eq. (6)). 

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). 

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. 

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. 

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