Successive approximations acetic acid example

The most successful example of generating chemicals directly from coal is the Tennessee Eastman integrated process for producing acetic anhydride. The commercial plant gasifies approximately 900 tons of coal per day and performs four chemical steps to yield annually 500 million pounds of acetic anhydride, 390 million pounds of methyl acetate, and 365 million pounds of methanol. In addition, 150 million pounds per year of acetic acid may be produced from acetic anhydride. 

Care must be taken in evaluating the ionic strength contribution of weak electrolytes. For example, if any of the solutions above contained phosphoric or acetic acid also, the ionic strength would be essentially the same, because only the dissociated phosphoric or acetic acids contributes, and this is generally very small. If, on the other hand, H3PO4 is the only solute present, then an approximate equilibrium calculation must be carried out (see Example 3.3), an ionic strength calculated, and the process repeated until values of I remain constant. This may take one or two successive approximations. 

Despite the fact that solvent effects on enzyme enantioselectivity appear to resist our efforts to rationalize their outcome using commonly accepted solvent descriptors, the effects are certainly there. An impressive example is provided in a report on the successful resolution of ds/trans-( 1 R,5 R)-bicyclo[3.2.0]hept-6-ylidene-acetate ethyl esters, intermediates in the synthesis of GABA (y-aminobutyric acid) analogs, by the Pfizer Bio transformations and Global R D groups (Scheme 2.2) [136]. From a screening protocol, CaLB was identified as a reactive catalyst for the hydrolysis of the racemic mixture of / //-os lor enantiomers with approximately equal activity for the ds- and tmns-isomers and a rather modest (E = 2.7) preference for the /Z-(lR,5R)-enantiomers. Application of medium engineering resulted in a phenomenal increase in the enantioselectivity (addition of 40% acetone, E > 200), while the ds- and trans-isomers were still converted at an almost equal rate. 

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