Ketone-water binary azeotropes

Methyl Vinyl Ketone. Methyl vinyl ketone [78-94-4] (3-buten-2-one) is a colorless Hquid with a pungent odor. It is stable only below 0°C, and readily polymerizes on standing at room temperature. It can be inhibited for storage and transportation by a mixture of acetic or formic acid and hydroquinone or catechol (266). This ketone is completely soluble in water, and forms a binary azeotrope with water (85 MVK 15 H2O vol %) at 75.8°C. 

The geometric properties of a RCM allow its simple sketch. Figure 9.5 shows the construction for the mixture methyl-isopropyl-ketone (MIPK), methyl-ethyl-ketone (MEK) and water. Firstly, the position of the binary azeotropes and of the ternary azeotrope is located. Then the boiling points for pure components and azeotropes are noted (Fig. 9.5a). The behaviour of characteristic points (node or saddle) is determined by taking into account the direction of temperatures. Finally, straight distillation boundaries are drawn by connecting saddles with the corresponding nodes (Fig. 9.5b). 

The problem at hand is how to remove water. Because ethanol and water form an azeotrope, it is possible to remove water from a reaction in this manner, but there are problems. Ethanol and water are miscible (mutually soluble in one another), so the water and ethanol do not separate (form layers) once the mixtrue has been distilled. If a solvent other than ethanol is used to form an azeotrope water and water is insoluble in that solvent, water would separate after the mixture had been distilled. One such solvent is benzene, which forms a binary (two-component) azeotrope with water (boiling point of benzene is 80.1°C) that boils at 69.4°C and is composed of a 91.1 8.9 benzenerwater mixture. Caution benzene is toxic and a suspected carcinogen see Chapter 21.) Refluxing the aldehyde or ketone with at least two equivalents of ethanol in benzene wiU drive the reaction toward the acetal (46) and the benzene-water azeotrope can be distilled off... 

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