Alkali oxides, acetone condensation

A number of solid base catalysts have been reported in the literature to be active for acetone condensation. These include alkali oxides (NajO, K O, CsjO) (7), alkaline earth oxides (MgO, CaO, BaO) (1,4-6), transition metal oxides (7) and phosphates (8-11), ion-exchange resins (12), zeolites (13) and clay minerals and hydrotalcites (HTC) (14,15). A suitable catalyst for the acetone-to-MIBK reaction must have several properties the condensation of acetone to DAA is catalyzed by either basic or acidic sites, the dehydration of DAA to MO is acid-catalyzed, and the selective hydrogenation of MO to MIBK requires appropriate metal sites (7,8). 

Even the trivial decomposition of oxaziridines may have some importance. In the oxidation of s-alkylamines to ketones conversion to the Schiff base of 2-pyridinealdehyde was proposed, followed by peracid oxidation to the oxaziridine (295). Decomposition by alkali yields the ketone added excess acetone suppresses condensation of pyridinealdehyde with dialkyl ketone (75AJC2547). 

Besides oxidative coupling of methane and double bond isomerization reactions (242), a limited number of organic transformations have been carried out with alkali-doped alkaline earth metal oxides, including the gas-phase condensation of acetone on MgO promoted with alkali (Li, Na, K, or Cs) or alkaline earth (Ca, Sr, or Ba) (14,120). The basic properties of the samples were characterized by chemisorption of CO2 (Table VI). 

In the three-step process acetone first undeigoes a liquid-phase alkali-catalyzed condensation to form diacetone alcohol. Many alkali metal oxides, metal hydroxides (eg, sodium, barium, potassium, magnesium, and lanthanium), and anion-exchange resins are described in the literature as suitable catalysts. The selectivity to diacetone alcohol is typically 90—95 wt % (64). In the second step diacetone alcohol is dehydrated to mesityl oxide over an acid catalyst such as phosphoric or sulfuric acid. The reaction takes place at 95—130°C and selectivity to mesityl oxide is 80—85 wt % (64). A one-step conversion of acetone to mesityl oxide is also possible. 

This is produced by the action of alkali upon an acetone solution of phenarsazine chloride, or by hydrolysis of the cyanide. It may also be obtained from diphenylamine by heating with arsenious oxide and phosphorus pentoxide at 160° to 170° C. for one hour, the mixture being mechanically stirred. When aniline and arsenious chloride are condensed in n-heptane solution, trianilinoarsine hydrochloride is formed, and this, when heated alone or in the presence of aniline, yields phenarsazine chloride, treatment of which with sodium hydroxide gives the oxide. The reaction may be represented as foUo-ws ... 

Benzalacetone has been obtained in small yield by drv distillation of a mixture of calcium acetate and calcium cinnamate (1) by heating the sodium derivative of cinnamaldehyde with methyl iodide (2) by heating cinnamaldehyde and methyl alcohol with zinc chloride (2) by heating acetone and benzaldehyde with acetic anhydride or zinc chloride (3). It is also formed when styrene and acetyl chloride are condensed by means of stannic chloride and the product is treated with diethylaniline (4) and when the vapors of cinnamic acid and acetic acid are passed together over ferric oxide at 470-490° (5). The only practical method, however, consists in condensing benzaldehyde and acetone by means of dilute aqueous alkali (6). 

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