3- propionaldehyd

The concept of homoenolization was recognized by Nickon in the 1960s but attempts at direct formation of homoenolates were frustrated by cyclopropanolate formation. This lack of success has prompted the development of homoenolate equivalents19 of which the first example, the 3-propionaldehyde anion equivalent (112), was previously discussed (Sections 1.2.2.1.2 and 1.2.2.1.3). Ghosez has shown that a-cyanoenamines (249 and 250) add preferentially in the 1,4(7)-mode to cycloalkenones. The versatility of (250) which serves as either a (3-carboxyvinyl anion equivalent [-CH=CHCChR] or 3-propionate anion equivalent ["Cl ClfcCChR] (Scheme 85) is notable.191... 

Fig. 5.3. Gas chromatogram of 2,4-dinitrophenylhydrazones of ten aliphatic aldehydes. Peaks 1 = formaldehyde 2 = acetaldehyde 3 = propionaldehyde 4 = acrolein 5 = isobutyraldehyde 6 = n-butyraldehyde 7 = isovaleraldehyde 8 = n-valeraldehyde 9 = crotonaldehyde 10 = n-capronaldehyde. For conditions see text. (Reproduced from / Chromatogr., 120 (1976) 379, by courtesy of Y. Hoshika.)...

Propionaldehyde. Use 34 g. (42-6 ml.) of n propyl alcohol, and a solution containing 56 g. of sodium chromate dihydrate, 300 ml. of water and 40 ml. of concentrated sulphuric acid. The experimental details are identical with those for n-butyraldehyde, except that the addition of the dichromate solution occupies 20 minutes, the temperature at the top of the column is not allowed to rise above 70-75°, and during the subsequent heating for 15 minutes the liquid passing over below 80° is collected the receiver must be cooled in ice. The yield of propionaldehyde, b.p. 47-50°, is 12 g. 

The glycidic esters are of interest primarily because upon hydrolysis aud decarboxylation they aflFord aldehydes (if ClCHjCOOEt is used) or ketones (if substituted chloroacetic esters- ClCHRCOOEt are employed) having a higher carbon content than the original aldehyde or ketone. Thus (I) gives o-phenyl-propionaldehyde or hydratropaldehyde (II) ... 

Starting from propionaldehyde the aldehyde H2C=CH-CH=C(CH3)CH=0 was obtained in an impure state and in moderate yield. Its precursor H2C=C=CH-CH(CH3)CH=0 was present in traces only. 

The attack of OH obeys the Markovnikov rule. Higher alkenes are oxidized to ketones and this unique oxidation of alkenes has extensive synthetic appli-cations[23]. The oxidation of propylene affords acetone. Propionaldehyde is... 

When the aldehyde group is directly attached to a carbon atom of a ring system, the suffix -carbaldehyde is added to the name of the ring system, e.g., 2-naphthalenecarbaldehyde. When the aldehyde group is separated from the ring by a chain of carbon atoms, the compound is named (1) as a derivative of the acyclic system or (2) by conjunctive nomenclature, for example, (1) (2-naphthyl)propionaldehyde or (2) 2-naphthalenepropionaldehyde. 

A cmde acetone product is recovered by distillation from the reaction mass. One or two additional distillation columns may be required to obtain the desired purity. If two columns are used, the first tower removes impurities such as acetaldehyde and propionaldehyde. The second tower removes undesired heavies, the major component being water. 

Although the selectivity of isopropyl alcohol to acetone via vapor-phase dehydrogenation is high, there are a number of by-products that must be removed from the acetone. The hot reactor effluent contains acetone, unconverted isopropyl alcohol, and hydrogen, and may also contain propylene, polypropylene, mesityl oxide, diisopropyl ether, acetaldehyde, propionaldehyde, and many other hydrocarbons and carbon oxides (25,28). 

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. 

Reduction. Because of a lack of discrimination between the double bond and carbonyl moieties, direct hydrogenation of acrolein leads to the production of mixtures containing propyl alcohol, C HgO [71-28-8] propionaldehyde, C H O [123-38-6J, and aHyl alcohol, C H O [107-18-16]. Both the... 

The vapor-phase reduction of acrolein with isopropyl alcohol in the presence of a mixed metal oxide catalyst yields aHyl alcohol in a one-pass yield of 90.4%, with a selectivity (60) to the alcohol of 96.4%. Acrolein may also be selectively reduced to yield propionaldehyde by treatment with a variety of reducing reagents. 

Reactions with Alcohols. The addition of alcohols to acrolein may be catalyzed by acids or bases. By the judicious choice of reaction conditions the regioselectivity of the addition maybe controlled and alkoxy propionaldehydes, acrolein acetals, or alkoxypropionaldehyde acetals produced in high yields (66). 

Hydroformylation of an olefin usiag synthesis gas, the 0x0 process (qv), was first commercialized ia Germany ia 1938 to produce propionaldehyde from ethylene and butyraldehydes from propylene (12). 

Aldehydes fiad the most widespread use as chemical iatermediates. The production of acetaldehyde, propionaldehyde, and butyraldehyde as precursors of the corresponding alcohols and acids are examples. The aldehydes of low molecular weight are also condensed in an aldol reaction to form derivatives which are important intermediates for the plasticizer industry (see Plasticizers). As mentioned earlier, 2-ethylhexanol, produced from butyraldehyde, is used in the manufacture of di(2-ethylhexyl) phthalate [117-87-7]. Aldehydes are also used as intermediates for the manufacture of solvents (alcohols and ethers), resins, and dyes. Isobutyraldehyde is used as an intermediate for production of primary solvents and mbber antioxidants (see Antioxidaisits). Fatty aldehydes Cg—used in nearly all perfume types and aromas (see Perfumes). Polymers and copolymers of aldehydes exist and are of commercial significance. 

Propionic acid made in butane LPO probably comes by a minor variation of reaction 38 that produces methyl radicals and propionaldehyde. It is estimated that up to 18% of the j -butoxy radicals may decompose in this manner (213) this may be high since propionic acid is a minor product. 

The mechanism of the cobalt-cataly2ed oxo reaction has been studied extensively. The formation of a new C—C bond by the hydroformylation reaction proceeds through an organometaUic intermediate formed from cobalt hydrocarbonyl which is regenerated in the aldehyde-forrning stage. The mechanism (5,6) for the formation of propionaldehyde [123-38-6] from ethylene is illustrated in Figure 1. 

Fig. 1. Mechanism for the unmodified cobalt oxo reaction which produces propionaldehyde from ethylene.

Union Carbide Corp. (Texas City, Tex.) propionaldehyde and valer-aldehyde 91 Rli... 

Chemicals responsible for odor in some PUR foams were synthesised by polymerisation of PO in CH2CI2 with Bp2(C2H )20 catalyst (114). The yield was 25% volatile material and 75% polymeric material. The 25% fraction consisted of dimethyldioxane isomers, dioxolane isomers, DPG, TPG, crown ethers, tetramers, pentamers, etc, and 2-ethy1-4,7-dimethyl-1,3,6-trioxacane (acetal of DPG and propionaldehyde). The latter compound is mainly responsible for the musty odor found in some PUR foams. This material is not formed under basic conditions but probably arises during the workup when acidic clays are used for catalyst removal. 

Miscellaneous Reactions. Ahyl alcohol can be isomerized to propionaldehyde [123-38-6] in the presence of sohd acid catalyst at 200—300°C. When copper or alumina is used as the catalyst, only propionaldehyde is obtained, because of intramolecular hydrogen transfer. On the other hand, acrolein and hydrogen are produced by a zinc oxide catalyst. In this case, it is considered that propionaldehyde is obtained mainly by intermolecular hydrogen transfer between ahyl alcohol and acrolein (31). 

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