Propionaldehyde, hydration

The mechanism in Figure 8 accounts for available information. At the active site of DDH, adenosylcobalamin exists with a small equilibrium amount of the 5 -deoxyadenosyl radical in complex 1. Abstraction of a hydrogen atom from Cl of the substrate by the nucleoside radical leads to 5 -deoxyadenosine and the substrate-related radical in complex 2. Radical rearrangement to the product-related radical in complex 3 is followed by abstraction of a hydrogen atom from the methyl group to regenerate the Co—C bond and form propionaldehyde hydrate in complex 4. Dehydration is followed by dissociation of propionaldehyde. 

Propanol has been manufactured by hydroformylation of ethylene (qv) (see Oxo process) followed by hydrogenation of propionaldehyde or propanal and as a by-product of vapor-phase oxidation of propane (see Hydrocarbon oxidation). Celanese operated the only commercial vapor-phase oxidation faciUty at Bishop, Texas. Since this faciUty was shut down ia 1973 (5,6), hydroformylation or 0x0 technology has been the principal process for commercial manufacture of 1-propanol ia the United States and Europe. Sasol ia South Africa makes 1-propanol by Fischer-Tropsch chemistry (7). Some attempts have been made to hydrate propylene ia an anti-Markovnikoff fashion to produce 1-propanol (8—10). However, these attempts have not been commercially successful. 

Addition. Addition reactions of ethylene have considerable importance and lead to the production of ethylene dichloride, ethylene dibromide, and ethyl chloride by halogenation—hydrohalogenation ethylbenzene, ethyltoluene, and aluminum alkyls by alkylation a-olefms by oligomerization ethanol by hydration and propionaldehyde by hydroformylation. 

In the examples of reductions of XCH2CHO mentioned above, hydration occurs both as antecedent and interposed reactions. The change of the second reduction step with pH is similar to that observed for acetaldehyde, but not quantitatively identical. This indicates that the second dehydration step is preceded here by a proton transfer. The rate of the proton transfer involving the carbanion formed as a primary electrolysis product governs the height of the acetaldehyde wave 84, 85). In the reduction of cinnamaldehyde, where only the hydration is interposed between the reductions of cinnamaldehyde and of 3-phenyl-propionaldehyde 87), the pH-dependence of the more negative wave of cinnamaldehyde is quantitatively identical with the pH-dependence of... 

Data for aliphatic aldehyde enolisation are very scarce, probably because the enolisation process is often complicated by oxidation and hydration. Nevertheless, the rate constants for base- and acid-catalysed iodination of R R2CHCHO were determined in aqueous chloroacetic acid-chloroacetate ion buffers (Talvik and Hiidmaa, 1968). The results in Table 4 show that alkyl groups R1 and R2 increase the acid-catalysed reactivity in agreement with hyperconjugative and/or inductive effects. This contrasts with aliphatic ketones for which steric interactions are important and even sometimes dominant. Data for base-catalysis are more difficult to interpret since a second a methyl group, from propionaldehyde to isobutyraldehyde, increases the chloroacetate-catalysed rate constant. This might result from a decrease of the a(C—H) bond-promoted hyperconjugative stabilisation of the carbonyl compound... 

Methyl hydrate. See Methyl alcohol Methyl hydratropaldehyde p-Methylhydratropaldehyde p-Methylhydratropic aldehyde. See 2-(p-Tolyl) propionaldehyde Methylhydrazine CAS 60-34-4 UN 1244... 

Benzaldehyde or propionaldehyde refluxed with excess 70%-hydrazine hydrate and KCN in alcohol until NHg-evolution ceases -> benzonitrile or propionitrile. Y 70-90%. W. Kohler, Z. Chem. 11, 343 (1971). 

The acid-catalyzed hydration of aUene gives acetone, not aUyl alcohol or propionaldehyde. 

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