Acetone diacetone alcohol, base-catalyzed

There are certain reactions, e.g. inversions of sucrose and methane etc. in which the rate of reactions were found to be proportional to the concentration of H+ ions. Similarly, there are reactions which are catalyzed by OH ions, e.g. conversion of acetone into diacetone alcohol or decomposition of nitroso-triacetoneamine. These are known as specific hydrogen ion catalyzed or specific hydroxyl-ion catalyzed reactions. Also there are some reactions in which both H+ and OFF ions act as catalysts probably along with water. The undissociated acid or base have negligible effect on the rate of reaction. The hydrolysis of ester is an example in which both H+ and OH ions act as catalyst... 

Aldol condensation of acetone is a well-known base-catalyzed reaction, and barium hydroxide is one of the catalysts for this reaction mentioned in textbooks. A family of barium hydroxide samples hydrated to various degress determined by the calcination temperature (473, 573, 873, and 973 K) of the starting commercial Ba(OH)2 8H2O were reported to be active as basic catalysts for acetone aldol condensation (282,286). The reaction was carried out in a batch reactor equipped with a Soxhlet extractor, where the catalyst was placed. The results show that Ba(OH)2 8H2O is less active than any of the other activated Ba(HO)2 samples, and the Ba(OH)2 calcined at 473 K was the most active and selective catalyst for formation of diacetone alcohol, achieving nearly 58% acetone conversion after 8h at 367 K in a batch reactor. When the reaction temperature was increased to 385 K, 78% acetone conversion with 92% selectivity to diacetone alcohol was obtained after 8h. The yield of diacetone alcohol was similar to that described in the literature in applications with commercial barium hydroxide, but this catalyst required longer reaction times (72-120 h) (287). No deactivation of the catalyst was observed in the process, and it could be used at least 9 times without loss of activity. 

Under base-catalyzed conditions, two molecules of acetone can condense to form diacetone alcohol. At room temperature (25 °C), about 5% of the acetone is converted to diacetone alcohol. Determine the value of AG° for this reaction. 

Methylisobutylketone (MIBK) which is used as solvent for inks and lacquers can be prepared from acetone through a catalytic three-step process base-catalyzed production of diacetone alcohol (DA), acid dehydration of (DA) into mesityloxide (MO) then hydrogenation of (MO) on a noble metal ... 

Ketones are chemically reactive and undergo acid- and base-catalyzed selfcondensation reactions. For acetone the base-catalyzed self-condensation reaction yields a product of diacetone alcohol [854] ... 

Since the anion-exchange resins are frequently used in the hydroxy form, certain precautions should be observed when employing them with non-aqueous solvents. If acetone is used, excessive diacetone alcohol may be formed via base-catalyzed aldol condensation. A small amount of water should be present in all organic solvents containing alcohol to repress transesterification of esters (15) and esterification of acids (16) with alcohol as solvent. Without water, up to 5% of transesterification in 15 to 20 min has been observed with DEAE-Sephadex. After an overnight contact the transesterification approached 35 %. With 1 % water in the solvent, however, less than 0.3% transesterification and 0.3% saponification occurred when 70 mg of butyl stearate was passed through a DEAE-Sephadex column (15). 

In the acid-catalyzed condensation of acetone, the enol is the intermediate, and it adds to the very strong Lewis acid, the protonated carbonyl group, to give initially the same product as the base-catalyzed reaction, diacetone alcohol (Fig. 19.73). Dehydration generally follows to give the a,P-unsaturated ketone, 4-methyl-3-penten-2-one (mesityl oxide). 

Base-catalyzed reactions were reviewed in general by Hattori [208,222], and from the reactions described butene isomerization, alcohol conversion, toluene alkylation, acetone condensation/diacetone alcohol decomposition, Knoevenagel condensations, diketone cyclization, ring transformation reactions, and dimerization of aldehydes to the corresponding esters were used to evaluate the acid-base properties in molecular sieves. 

Scheme 14 Base-catalyzed reaction of acetone to diacetone alcohol...

Base catalyzed reaction has been covered with reference to transesterification to make biodiesel. A classical case of considerable practical importance is the side chain alkylation of toluene with propylene to give isobutyl benzene, apart from conversion of acetone to diacetone alcohol and isophorone and even here heterogenerous versions are in vogue or under consideration. Microwave assisted reactions are duly covered and it would have been useful to cover ultrasonically assisted reactions, particularly when solid reactant/ catalyst is involved. 

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