Equilibrium plus alcohol

In fact, acetal formation is even more difficult than ester formation while the equilibrium constant for acid-catalysed formation of ester from carboxylic acid plus alcohol is usually about 1, for... 

In fact, acetal formation is even more difficult than ester formation while the equilibrium constant for acid-catalysed formation of ester from carboxylic acid plus alcohol is usually about 1, for acetal formation from an aldehyde and ethanol (shown above), the equilibrium constant is fC = 0.0125. For ketones, the value is even lower in fact, it is often very difficult to make the acetals of ketones (sometimes called ketals) unless they are cyclic (we consider cyclic acetals later in the chapter). However, there are several techniques that can be used to prevent the water produced in the reaction from hydrolysing the product. 

Substituted acrylic monomers. The reactants (methyl acrylate plus alcohol or amine) were added neat or in a non-aqueous solvent together with Novozym 435 immobilized lipase from Candida antarctica as a catalyst. Molecular sieves (4A) were used to remove water in order to shift the reaction equilibrium to product formation, and also to eliminate side reactions due to Michael addition that was usually enhanced by the presence of water or methanol. Unreacted starting materials were removed by evaporation, and the monomer products obtained without further purification. TLC analysis indicated that the desired products had formed. The purity of the products was confirmed by NMR and IR analysis. The two monomers were successfully polymerized in a separate step. 

Since the acetal exists in equilibrium with the aldehyde, it is possible for the aldehyde to be released when water is added in a mixed drink, changing the balance and giving a burst of freshness to a mixed drink. Ethyl esters of terpene alcohols in citrus oils and other botanicals, plus the ethyl esters of fatty and volatile acids, are formed during prolonged exposure to ethyl alcohol. Certain beverage alcohol products that need to contain milk, eggs, or other protein containing materials must be developed carefully and the added flavors must be considered to prevent the precipitation of the protein and separation of the product. 

Pinachrome. 0.02% solution of the indicator in 40% alcohol, or a solution of the hydrochloric acid salt in water (20 mg. indicator in 10 c.c. alcohol, plus 3.8 c.c. 0.01 N HCl, diluted to 100 c.c. with water). The solution should be stored in resistance glass. The range of applicability is 5.8-7.8 (colorless to red). Because the color equilibrium is not established instantaneously, the solutions should be allowed to stand for two minutes after addition of indicator and before measurements are made. The alkaline comparison solutions cannot be kept for more than about an hour because the free base is too insoluble. Such solutions must be prepared carefully in 0.01 N sodium carbonate solutions, the content of the tubes being mixed by gentle rotation. Vigorous shaking causes the indicator to separate out at the surface. 

Carbon dioxide is separated from methyl alcohol in a stripping column. The saturated liquid feed enters the top tray at 100 kmole/min. Equilibrium is governed by T = 2X. If three ideal trays plus reboiler are used find the following items (assuming column liquid and vapor rates are constant). Feed and overhead vapor compositions when Xb =0.01 and... 

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