Acetaldehyde and Acetone

In the two-stage process the alkene is reacted with the catalyst system (100-110°C, 10 atm). The reduced catalyst solution containing Cu2Cl2 is reoxidized with air in a second reactor under the same conditions. In both cases about 95% oxo yield is achieved at 95-99% alkene conversion. Because of the explosion hazard of mixing ethylene or propylene with pure oxygen, most commercial operations favor the less hazardous two-stage process. 

In the process jointly developed by Bayer and Hoechst,933-935 a palladium-gold-on-silica or alumina catalyst impregnated with KOAc is used. A mixture of ethylene, acetic acid, and oxygen is converted at 150-170°C and about 5-10 atm to produce vinyl acetate with about 91-92% selectivity at about 10% conversion in a highly exothermic reaction. The only major byproduct is C02. KOAc requires continuous replenishment. A similar process was independently developed by U.S.I. Chemicals.932 936 

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To a few drops of formalin solution add a few drops of dinitro-phenylhydrazine reagent A (p. 263) a yellow precipitate is produced in the cold. Acetaldehyde and acetone give orange-coloured precipitates. Dissolve water-insoluble compounds e.g-y benzaldehyde, salicylalde-hyde, acetophenone and benzophenone) in a small volume of methanol before adding reagent B. With benzophenone the precipitate forms slowly. 

Acrolein is produced according to the specifications in Table 3. Acetaldehyde and acetone are the principal carbonyl impurities in freshly distilled acrolein. Acrolein dimer accumulates at 0.50% in 30 days at 25°C. Analysis by two gas chromatographic methods with thermal conductivity detectors can determine all significant impurities in acrolein. The analysis with Porapak Q, 175—300 p.m (50—80 mesh), programmed from 60 to 250°C at 10°C/min, does not separate acetone, propionaldehyde, and propylene oxide from acrolein. These separations are made with 20% Tergitol E-35 on 250—350 p.m (45—60 mesh) Chromosorb W, kept at 40°C until acrolein elutes and then programmed rapidly to 190°C to elute the remaining components. 

Methylated spirit contains, in addition to ethyl and methyl alcohols, water, fusel-oil, acetaldehyde, and acetone. It may be freed from aldehyde by boiling with a—3 per cent, solid caustic potash on the water-bath with an upright condenser for one hour, or if larger quantities are employed, a tin bottle is preferable, which is heated directly over a small flame (see Fig. 38). It is then distilled with the apparatus shown in Fig. 39. The bottle is here surmounted with a T-piece holding a thermometer. The distillation is stopped when most of the spirit has distilled and the thermometer indicates 80°. A further purification may be effected by adding a little powdered permanganate of potash and by a second distillation, but this is rarely necessary. The same method of purification may be applied to over-proof spirit, which will henceforth be called spirit as distinguished from the purified product or absolute alcohol. 

Shara MA, Dickson PH, Bagchi D, et al. 1992. Excretion of formaldehyde, malondialdehyde, acetaldehyde and acetone in the urine of rats in response to 2,3,7,8-tetrachlorodibenzo-p-dioxin, paraquat, endrin and carbon tetrachloride. J Chromatography 576 221-233. 

Slemr, J., W. Junkermann, and A. Volz-Thomas, Temporal Variations in Formaldehyde, Acetaldehyde, and Acetone and Budget of Formaldehyde at a Rural Site in Southern Germany, Atmos. Environ., 30, 3667-3676 (f996). 

Formaldehyde, acetaldehyde, acetone, and carbon monoxide were common combustion products of the four hexanes. Propionaldehyde, n-butyraldehyde, acrylic aldehyde, crotonic aldehyde, and methyl ethyl ketone were all found as intermediates in the combustion of n-hcxane. Acetaldehyde and acetone were prominent and propionaldehyde and acrylic aldehyde were present among the intermediates from 2-methylpentane. Acetaldehyde and methyl ethyl ketone were peculiarly characteristic of 3-methyl-pentane and acetaldehyde, acetone, and pivalic aldehyde were characteristic of 2,2-dimethylbutane. In other words, the intermediate monocarbonyl combustion products... 

The result of this bonding would be a greater negative charge on the hydroxyl oxygen, a condition that should reduce the ionizability of the C—H bond. The low ionizabilities of glyceraldehyde and dihydroxy-acetone, compared with those of acetaldehyde and acetone, respectively, could reflect a tendency for the hydroxy compounds to exist as cyclic dimers. Only the monomeric form would be expected to give a carbanion. 

Oxygen-transfer reactions have been shown to occur from cobalt(III)-nitro complexes to alkenes coordinated to palladium.472 Thus ethylene and propene have been oxidized stoichiometrically in quantitative yields to acetaldehyde and acetone respectively, with the concomitant reduction of the nitro- to the nitrosyl-cobalt analog. A catalytic transformation with turnover numbers of 4-12 can be achieved at 70 °C in diglyme. The mechanism shown in Scheme 11 has been suggested. 

Formaldehyde, acetaldehyde, and acetone are important commercial chemicals, synthesized by special methods. In the laboratory, aldehydes and ketones are most commonly prepared by oxidizing alcohols, but they can also be prepared by hydrating alkynes and by Friedel-Crafts acylation of arenes. Aldehydes and ketones occur widely in nature (see Figure 9.1). 

Pd-containing aluminophosphate molecular sieves have been used to carry out crossed aldol condensations between an aldehyde and a ketone by using a 0.5 % Pd/ MnAPSO-31 catalyst in a vapour-phase fixed bed reactor.[14] Thanks to the excess of the ketone with respect to the aldehyde (4 1), it is possible to get high selectivity to the desired product, i.e. 70 % of heptan-2-one from n-butyraldehyde and acetone and 89 % of pentan-2-one from acetaldehyde and acetone, the major by-product being, in both cases, MIBK from acetone self-condensation. 

Quantitative measurements were also performed for formaldehyde, acetaldehyde, and acetone (141) because these compounds are likely to be formed by the oxidation of common organic pollutants found in air. Although these carbonyl compounds can easily be further oxidized, their high volatility allows them to be significantly desorbed from Ti02, unlike the corresponding carboxylic acids with the same numbers of C atoms. For formaldehyde and a given series of measurements, the concentration (in... 

Compound (1) and 2-methyl-1//-pyrrolo[2,3-Z>]pyridine (87) have been prepared by a heterogeneous catalyzed Fischer reaction. A cyclization reaction occurred with acetaldehyde and acetone 2-pyridylhydrazones in the presence of y-alumina and fluorinated aluminum oxide (Equation (20)). In addition to the desired pyrrolopyridine products, 2-aminopyridine (88) and a triazine derivative (89) were also formed. Use of the fluorinated aluminum oxide maximized formation of the desired products <72CHE594, 72CHE1037). 

Because of this hydrogen bonding, ketones and aldehydes are good solvents for polar hydroxylic substances such as alcohols. They are also relatively soluble in water. Table 18-3 shows that acetaldehyde and acetone are miscible (soluble in all proportions) with water. Other ketones and aldehydes with up to four carbon atoms are fairly soluble in water. These solubility properties are similar to those of ethers and alcohols, which also engage in hydrogen bonding with water. 

The Franck-Condon factors determination is of special interest when the two electronic states, involved in the transition exhibit very different geometries. This is especially the case of electronic transition in the valence shell such as n — tt, which induces conjugation change, as well as geometrical change, in the molecular system. This phenomenon was studied in the fluorescence spectra of acetaldehyde and acetone [62,63], and in the phosphorescence spectra of thioacrolein and thioacetaldehyde [64,65] and thioacetone [66]. 

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