Propionaldehyde—continued

A. Diethyl propionylsuccinate (1). A solution of 412 g. (2.4 mole) of diethyl maleate (Note 1), 278 g. (4.8 mole) of freshly distilled propionaldehyde (Note 2), and 1.2 g. (0.0048 mole) of benzoyl peroxide in a normal 2-1. Pyrex flask is heated under reflux while undergoing irradiation with an ultraviolet lamp (Note 3). The initial reflux temperature is 60°. After 2 hours another 1.2 g. (0.0048 mole) of benzoyl peroxide is added. Strong reflux and irradiation are maintained throughout the entire reaction period. After 18 hours total time, the internal pot temperature reaches 68°. At this point the last 1.2 g. (0.0048 mole) of benzoyl peroxide is added, and the reaction is continued for a total of 30 hours, at which time the pot temperature reaches 74.5°. The reflux condenser is then replaced by a distillation head. The excess propionaldehyde (119 g.) is distilled under atmospheric pressure, b.p. 48-49°. Succinate 1 is distilled under reduced pressure. The main fraction, b.p. 145-151.5° (15-16 mm), provides 417-449 g. (75-81%) of product having sufficient purity for use in the next step (Note 4). 

Isomorphous replacement in isotactic polyaldehydes was shown by A. Tanake, Y. Hozumi, K. Hatada, S. Endo, and R. Fujishige (42). These authors studied the binary polymer systems formed by acetaldehyde, propionaldehyde, n-butyraldehyde, iso-butyraldehyde and w-heptanal. All the copolymers are crystalline over the whole range of compositions. In the case of binary copolymers of acetaldehyde, propionaldehyde and K-butyraldehyde the unit cells have the same tetragonal space group UJa, with the same chain axis (4.8 A), while the dimensions of the a axis change continuously as a function of the copolymer composition. In the case of copolymers of isobutyraldehyde with other aldehydes, the continuous variation of the lattice constants a and c were observed. 

Other aliphatic aldehydes have been identified and quantitatively measured in various brandies (31, 32). These include small amounts of formaldehyde, propionaldehyde, isobutyraldehyde, isovaleraldehyde, furfural, etc. Furfural is a normal component of pot-still distillates, but its presence in continuous still brandies is negligible before aging in wood. 

A mixture of 288 g (4 mols) of isobutyraldehyde, 288 g of methanol was cooled to 10°C and 170 g (2 mols) of 36.6% formalin containing 8.5 g (3% based on isobutyraldehyde) of sodium hydroxide was added dropwise over a 55 minute period to produce alpha,alpha-dimethyl-beta-hydroxy-propionaldehyde. The mixture was stirred for an additional 2 hours at 10-15°C and then contacted with acetic acid to neutralize the catalyst. The excess isobutyraldehyde and methanol were stripped off at a kettle temperature of 50°C at 25 mm. To the residual a,a-dimethyl-beta-hydroxypropionaldehyde a mixture of 260 ml of methanol and 2 g (0.75%) sodium cyanide was added and the solution cooled to 10°C before adding 59.4 g (2.2 mols) of hydrogen cyanide dropwise over a 35 minute period to produce a,y-dihydroxy-p,p-dimethylbutyronitrile. The mixture was stirred at 10°C for one hour period and then contacted with acetic acid to neutralize the catalyst before stripping off the excess methanol to a kettle temperature of 45°C at 18 mm. The crude cyanohydrin was then hydrolysed by heating with 4 mols of concentrated hydrochloric acid at 80°C for 2 hours, then diluting with an equal volume of water and heating at 100°C for an additional 8 hours. The aqueous mixture was extracted continuously with ethylene dichloride. The solvent was... 

Conditions Entries 1-3 To a mixture of ArCHO (0.5 mmol), 4-methoxyaniline (0.5 mmol), and (S)-proline (0.15 mmol) in DMF (3 mL), donor aldehyde (5.0 mmol) in DMF (2 mL) was slowly added (0.2 mL min-1) at —20 °C. The mixture was stirred at the same temperature for 4-10 h. The mixture was diluted with Et20 and reduction performed by addition of NaBH4 [71b]. Entries 4 and 5 After stirring a solution of ArCHO (1.0 mmol), 4-methoxyaniline (1.1 mmol), and (S)-proline (0.1 mmol) in N-methyl-2-pyrrolidinone (1.0 mL) for 2 h at rt, propionaldehyde (3.0 mmol) was added to the mixture at -20 °C, and stirring was continued for 20 h at the same temperature. The reaction was worked-up and reduction with NaBH4 performed without purification [82]. 

Method B After stirring a solution of ArCHO (1.0 mmol), 4-methoxyaniline (1.1 mmol), and (S)-proline (0.1 mmol) in N-methyl-2-pyrrolidinone (1.0 mL) for 2 h at r.t., propionaldehyde (3.0 mmol) was added to the mixture at — 20 °C, and stirring continued for 20 h at the same temperature. The reaction was worked-up and reduction with NaBH4 was performed without purification. 

A 1% aqueous solution of sodium hydroxide (1.2 1.) is placed in a 2-1. flask and cooled to 8°. An atmosphere of carbon dioxide is maintained in the flhsk and the contents are stirred at high speed (2000-3000 r.p.m.) while a mixture of 60 g. (1.03 moles) of propionaldehyde and 45 g. (1.02 moles) of acetaldehyde is added. The temperature is not allowed to rise over 10°, and stirring is continued for 1 hour. The mixture is neutralized with acetic acid and extracted with ether the ethereal extract is dried over calcium chloride and distilled. There is obtained 26 g. (SO o) of the aldehyde boiling at 116-119°. The compound is decomposed rapidly in contact with air. 

Figure 8.16 Peak height as a function of the oxidation potential FI for formic acid (lOOmg/L), formaldehyde (100 mg/L), acetaldehyde (300 mg/L), and propionaldehyde (300 mg/L) continuous line background current.

Currently, propionic acid is produced by a petrochemical production way. The process is called oxo process. Ethylene reacts with synthesis gas (CO/H2) to propionaldehyde which reacts with oxygen to propionic acid. Because of the raising oil price and the pursuit for oil independency and sustainable granting of industry appreciable chemicals, the public demand for biotechnological production of propionic acid is raised continuously for the last few years. 

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