Hydrogenation 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. 

Oldenburg and Rase AIChE J., 3 (462), 1957] studied the catalytic vapor phase hydrogenation of propionaldehyde by making low conversion runs on a commercial supported... 

Use of the same complexes to catalyze the hydrogenation of propionaldehyde showed that [RuH(Cl)(PPh3)3] (3) was the most effective. However, complex (11) was preferred for general use because of its stability in air.38 Turnover numbers up to 32 000 were achieved. Complex (11) decomposed during the reactions to give a variety of species which could not be characterized. 

The kinetics of the hydrogenation of propionaldehyde was investigated on different transition metals325. The catalytic activity of the metals studied changes in the sequence... 

Propionaldehyde is produced by the oxo reaction of ethylene with carbon monoxide and hydrogen. n-Propyl alcohol is produced by hydrogenation of propionaldehyde, and propionic acid is made by oxidation of propionaldehyde. 

For the hydrogenation of propionaldehyde (CH3CH2CHO) to propanol (CH3CH2CH2OH) over a supported nickel catalyst, assume that the rate-limiting step is the reversible chemisorption of propionaldehyde and that dihydrogen adsorbs dissociatively on the nickel surface. 

Hydrogenation of propionaldehyde, catalyzed by various ruthenium-TPPTS complexes, was dramatically influenced by the addition of certain salts [122, 123]. Whereas in the absence of salts there was no reaction at 35 °C and 50 bar H2, in the presence of Nal TOFs of more than 2000 h 1 were determined. This was lowered to 300 h-1 when the sodium cation was selectively sequestered by a cryptant (4,7,13,16,21-pentoxa-l,10-diazabicyclo[5.8.8]tricosane). Obviously, the larger part of the salt effect belonged to the cation. It was concluded that electrophilic assistance by Na+ facilitated C-coordination of the aldehyde and formation of a hydroxy-alkyl intermediate. 

Several water-soluble ruthenium complexes, with P = TPPMS, TPPTS, or PTA ligands (cf. Section 2.2.3.2), catalyze the selective reduction of crotonaldehyde, 3-methyl-2-butenal (prenal), and trans-cinnamaldehyde to the corresponding unsaturated alcohols (Scheme 2) [33—36]. Chemical yields are often close to quantitative in reasonable times and the selectivity toward the aUyhc alcohol is very high (> 95%). The selectivity of the reactions is critically influenced by the pH of the aqueous phase [11] as well as by the H2 pressure [37]. The hydrogenation of propionaldehyde, catalyzed by Ru(II)/TPPTS complexes, was dramatically accelerated by the addition of inorganic salts [38], too. In sharp contrast to the Ru(II)-based catalysts, in hydrogenation of unsaturated aldehydes rhodium(I) complexes preferentially promote the reaction of the C=C double bond, although with incomplete selectivity [33, 39]. 

Oldenberg and Rase (13) studied the catalytic vapor-phase hydrogenation of propionaldehyde to propanol over a commercially snpported nickel catalyst. Their data indicate that at 150°C the mathematical form of the reaction rate (at very low conversions) can be expressed qnite well as... 

Fig. 10. Influence of the CO partial pressure (atm) on the reaction rate of hydrogenation of propionaldehyde in contact with dicobalt octacarbonyl (0.2 mole % Co), (Ph2— 95 atm), a = Initial concentration of aldehyde,...

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... 

With Unsaturated Compounds. The reaction of unsaturated organic compounds with carbon monoxide and molecules containing an active hydrogen atom leads to a variety of interesting organic products. The hydroformylation reaction is the most important member of this class of reactions. When the hydroformylation reaction of ethylene takes place in an aqueous medium, diethyl ketone [96-22-0] is obtained as the principal product instead of propionaldehyde [123-38-6] (59). Ethylene, carbon monoxide, and water also yield propionic acid [79-09-4] under mild conditions (448—468 K and 3—7 MPa or 30—70 atm) using cobalt or rhodium catalysts containing bromide or iodide (60,61). 

A mixture of 2.9 grams of 5-chloro-2,4-disulfamvl-aniline in 20 ml of anhydrous diethylene-glycol dimethylether, 0.44 gram of propionaldehyde and 0.5 ml of a solution of hydrogen chloride in ethyl acetate (109.5 grams hydrogen chloride per 1,000 ml) Is heated to 80° to 90°C and maintained at that temperature for 1 hour. The reaction mixture is concentrated under reduced pressure on addition of water, the product separates and is then recrystal-lized from ethanol or aqueous ethanol to yield the desired 6-chloro-3-ethvl-7-sulfamyl-3,4-dihydro-1,2,4-benzothiadiazine-1,1-dioxide, MP 269° to 270°C. 

It has been suggested that the rate limiting step in the mechanism is the chemisorption of propionaldehyde and that the hydrogen undergoes dissociative adsorption on nickel. Determine if the rate expression predicted by a Hougen-Watson model based on these assumptions is consistent with the experimentally observed rate expression. 

The simplest a,/3-unsaturated aldehyde, acrolein, gives nearly quantitative yields of the hydrogenation product propionaldehyde under hydroformylation conditions. Most of the research has been conducted on acetal or acetate derivatives. 

The cationic tungsten dihydride [Cp(CO)2(PMe3)W(H)2]+ hydrogenates the C=0 bond of propionaldehyde within minutes at 22 °C, leading to the formation of cis and truns isomers of Cp(CO)3W(l IO"Pr) Oif (Eq. (28)) [42]. The cis isomer of the alcohol complex released the free alcohol faster than the trans isomer. A similar stoichiometric ionic hydrogenation of acetone was also observed using [Cp(CO)2(PMe3)W(H)2]+. 

In this case, the enthalpies of reaction are 52.1, 45.7 and 44.6kJmoD where the enthalpies of formation of solid and gaseous acetone oxime are from References 1 and 4, respectively, and the enthalpies of oximation in aqueous media are from References 49a and 49c. In both cases, the values are comfortably similar for the three phases. Perhaps we should not be too surprised that the values are close—after all, the number of hydrogen bonds are the same on the two sides of the reaction. However, nothing prepares us for the observation that the aqueous phase oximation enthalpy of propionaldehyde is 73.2 kJmoD, even though we recall problems with the enthalpy of formation of EtCH=NOH. 

Reaction of various aldehydes with hydrogen sulfide leads to substituted thiophenes, dihydrothiophenes, dithiolanes and trithiolane, as well as to six-membered ring thiopyran derivatives and dithiins. Ledl (33) obtained 2,4-dimethylthiophene (1, R Me) as a product of the reaction of propionaldehyde with hydrogen sulfide in the presence of ammonia. Sultan (29) reported the formation of 2,4-diethylthiophene (1, R - Et), 2,4-dibutyl-thiophene (1, R - Bu), and their dehydro derivatives from the reaction of ammonium sulfide with butyraldehyde and caproaldehyde (hexanal), respectively. The mechanism suggested for their formation is depicted in Scheme 1. Space limitations do not allow us to discuss the mechanism here in detail (for additional information, see ref. 29). 

The preparation of tertiary amines by reductive alkylation of ammonia appears to find only limited application. Triethylamine and tripropylamine were prepared by hydrogenation of acetaldehyde and propionaldehyde, respectively, in the presence of ammonia over platinum catalyst.38 A high yield (84.1% by GC) of trinonylamine was... 

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