Acetone reaction with Call

With aldehydes, primary alcohols readily form acetals, RCH(OR )2. Acetone also forms acetals (often called ketals), (CH2)2C(OR)2, in an exothermic reaction, but the equiUbrium concentration is small at ambient temperature. However, the methyl acetal of acetone, 2,2-dimethoxypropane [77-76-9] was once made commercially by reaction with methanol at low temperature for use as a gasoline additive (5). Isopropenyl methyl ether [116-11-OJ, useful as a hydroxyl blocking agent in urethane and epoxy polymer chemistry (6), is obtained in good yield by thermal pyrolysis of 2,2-dimethoxypropane. With other primary, secondary, and tertiary alcohols, the equiUbrium is progressively less favorable to the formation of ketals, in that order. However, acetals of acetone with other primary and secondary alcohols, and of other ketones, can be made from 2,2-dimethoxypropane by transacetalation procedures (7,8). Because they hydroly2e extensively, ketals of primary and especially secondary alcohols are effective water scavengers. 

Later in the 20th century, Vompe and Stepanov delineated efficient procedures for the preparation of the so-called Zincke salts (e.g., 1) from pyridines and 2,4-dinitrochlorobenzene, involving, for example, reflux in acetone. Vompe and Lukes also noted that electron-donating substituents on the pyridinium ring of the Zincke salt retarded reaction with amines at the 2-position of the pyridinium ring, sometimes leading instead to attack at the C-1 position of the 2,4-dinitrobenzene ring, with displacement of the pyridine. 

Protective Groups for Diols. Diols represent a special case in terms of applicable protecting groups. 1,2- and 1,3-diols easily form cyclic acetals with aldehydes and ketones, unless cyclization is precluded by molecular geometry. The isopropylidene derivatives (also called acetonides) formed by reaction with acetone are a common example. 

Mixed or crossed aldol condensation Aldol condensations between different carbonyl reactants are called crossed (or mixed) reactions. Crossed aldol condensation works well if one carbonyl compound has no a-hydrogen(s). For example, acetone reacts with furfural in a crossed-aldol reaction to give the corresponding a,P-unsaturated ketone 3.15. 

Dehydrogenation with selenium dioxide gives the l,4-dien-3-one (19-1). The great majority of such glycols are commonly used as their 16,17-cyclic acetals with some small ketone. In the case at hand, reaction with acetone gives the acetal 19-2, that group often being called an acetonide. 

Another variation of this classic reaction is called the aldol-transfer reaction, reported by Nevalainen. In the presence of a suitable catalyst, usually an aluminum compound, an aldol product reacts with an aldehyde, gen-erating a ketone and a new aldol. An example is the reaction of benzaldehyde with aldol 143 in the pres-ence of 5% of aluminum catalyst (144). In dichloromethane at ambient temperatures, a 62% yield of aldol 145 was obtained after a reaction time of 43 h. The other product of this reaction was acetone, which was readily removed. This transformation involves a retro-aldol reaction of 143 (see sec. 9.5.A.vi.) and the resul-tant enolate anion reacts with benzaldehyde. This reaction has been done with several aldehydes and 143 is particularly attractive (the aldol condensation product of acetone), because acetone is the second product. 

Since an acetal is produced by the reaction of a carbonyl with a diol, an acetal can serve as a protective group for either functional group. Deprotection is accomplished as usual by treatment with acid and water hydrolysis of the acetal regenerates both the carbonyl and the diol. Both 1,2- and 1,3-Diols can be protected by reaction with acetone and acid. The resulting cyclic acetal (called an acetonide) is widely used in carbohydrate chemistry to selectively mask pairs of hydroxyl groups in sugars. 

In 1843, Pira [1] reported that phenol alcohols are converted to resins (called saliretins) on heating. Baeyer [2] in 1872 reported that the reaction of phenols with acetaldehyde in the presence of acid catalysts also gives resinous products. Kleeberg [3] in 1891 reported that formaldehyde undergoes similar reactions. However, Dianin [4, 5] found that acetone reacts with phenol to give a crystalline bisphenol (now known as bisphenol A). In 1874 Lederer [6] and Manasse [7] independently synthesized o-hydroxybenzyl alcohol (saligenin) by the low-temperature alkaline-catalyzed formaldehyde reaction. 

Internal alkynes can be converted to trans alkenes using sodium (or lithium) in liquid ammonia. The reaction stops at the alkene stage because sodium (or lithium) reacts more rapidly with triple bonds than with double bonds. This reaction is called a dissolving metal reduction. Ammonia is a gas at room temperature (bp = — 33 °C), so it is kept in the liquid state by cooling the reaction flask in a dry ice/acetone mixture, which has a temperature of -78 °C. 

Six-membered heterocycles with two heteroatoms are prepared by reaction of diketene with a substrate containing a C—O or C—N multiple bond. With carbonyl compounds diketene reacts in the presence of acids to give l,3-dioxin-4-ones. The best known is 2,2,6-trimethyl-4H-l,3-dioxin-4-one [5394-63-8] (15), the so-called diketene—acetone adduct, often used as a diketene replacement that is safer to handle and to transport, albeit somewhat less reactive than diketene itself (103,104), forming acetylketene upon heating. 

If (A i[X ]/A 2[Y ]) is not much smaller than unity, then as the substitution reaction proceeds, the increase in [X ] will increase the denominator of Eq. (8-65), slowing the reaction and causing deviation from simple first-order kinetics. This mass-law or common-ion effect is characteristic of an S l process, although, as already seen, it is not a necessary condition. The common-ion effect (also called external return) occurs only with the common ion and must be distinguished from a general kinetic salt effect, which will operate with any ion. An example is provided by the hydrolysis of triphenylmethyl chloride (trityl chloride) the addition of 0.01 M NaCl decreased the rate by fourfold. The solvolysis rate of diphenylmethyl chloride in 80% aqueous acetone was decreased by LiCl but increased by LiBr. ° The 5 2 mechanism will also yield first-order kinetics in a solvolysis reaction, but it should not be susceptible to a common-ion rate inhibition. 

The reverse reaction, the so-called Oppenauer oxidation, is carried out by treating a substrate alcohol with aluminum tri-r-butoxide in the presence of acetone. By using an excess of acetone, the equilibrium can be shifted to the right, yielding the ketone 1 and isopropanol ... 

Halide exchange, sometimes call the Finkelstein reaction, is an equilibrium process, but it is often possible to shift the equilibrium." The reaction is most often applied to the preparation of iodides and fluorides. Iodides can be prepared from chlorides or bromides by taking advantage of the fact that sodium iodide, but not the bromide or chloride, is soluble in acetone. When an alkyl chloride or bromide is treated with a solution of sodium iodide in acetone, the equilibrium is shifted by the precipitation of sodium chloride or bromide. Since the mechanism is Sn2, the reaction is much more successful for primary halides than for secondary or tertiary halides sodium iodide in acetone can be used as a test for primary bromides or chlorides. Tertiary chlorides can be converted to iodides by treatment with excess Nal in CS2, with ZnCl2 as catalyst. " Vinylic bromides give vinylic iodides with retention of configuration when treated with KI and a nickel bromide-zinc catalyst," or with KI and Cul in hot HMPA." ... 

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