Acetaldehyde, reaction with ammonia

Reactions with Ammonia and Amines. Acetaldehyde readily adds ammonia to form acetaldehyde—ammonia. Diethyl amine [109-87-7] is obtained when acetaldehyde is added to a saturated aqueous or alcohoHc solution of ammonia and the mixture is heated to 50—75°C in the presence of a nickel catalyst and hydrogen at 1.2 MPa (12 atm). Pyridine [110-86-1] and pyridine derivatives are made from paraldehyde and aqueous ammonia in the presence of a catalyst at elevated temperatures (62) acetaldehyde may also be used but the yields of pyridine are generally lower than when paraldehyde is the starting material. The vapor-phase reaction of formaldehyde, acetaldehyde, and ammonia at 360°C over oxide catalyst was studied a 49% yield of pyridine and picolines was obtained using an activated siHca—alumina catalyst (63). Brown polymers result when acetaldehyde reacts with ammonia or amines at a pH of 6—7 and temperature of 3—25°C (64). Primary amines and acetaldehyde condense to give Schiff bases CH2CH=NR. The Schiff base reverts to the starting materials in the presence of acids. 

As in the synthesis of other bipyridines, several routes to 4,4 -bipyridine have been devised where one of the pyridine rings is built up from simpler components. For example, a dimer of acrolein reacts with ammonia and methanol in the presence of boron phosphate catalyst at 350°C to give a mixture of products including 4,4 -bipyridine (3.4% yield), and in a reaction akin to ones referred to with other bipyridines, 4-vinylpyridine reacts with substituted oxazoles in the presence of acid to give substituted 4,4 -bipyridines. ° ° Condensation of isonicotinaldehyde with acetaldehyde and ammonia at high temperatures in the presence of a catalyst also affords some 4,4 -bipyridine, and related processes give similar results,whereas pyran derivatives can be converted to 4,4 -bipyridine (56% conversion), for example, by reaction with ammonia and air at 350°C with a nickel-alumina catalyst. Likewise, 2,6-diphenyl-4-(4-pyridyl)pyrylium salts afford 2,6-... 

Addition Products.—An important property of aldehydes is that they readily take up certain compounds and form addition products. When acetaldehyde reacts with ammonia, sodium acid sulphite or hydrogen cyanide definite crystalline compounds are obtained. The probable reaction is that the double union between carbon and oxygen is broken the oxygen being converted into hydroxyl, while the remainder of the added compound satisfies the other valence as follows ... 

The reaction of ethanol with ammonia on zeolite catalysts leads to ethylamine. If, however, the reaction is carried out in the presence of oxygen, then pyridine is formed [53]. MFI type catalysts H-ZSM-5 and B-MFI are particularly suitable for this purpose. Thus, a mixture of ethanol, NH3, H2O and O2 (molar ratio 3 1 6 9) reacts on B-MFI at 330 °C and WHSV 0.17 h 1 to yield pyridine with 48 % selectivity at 24 % conversion. At 360 °C the conversion is 81% but there is increased ethylene formation at the expense of pyridine. Further by-products include diethyl ether, acetaldehyde, ethylamine, picolines, acetonitrile and CO2. When applying H-mordenite, HY or silica-alumina under similar conditions pyridine yields are very low and ethylene is the main product. The one-dimensional zeolite H-Nu-10 (TON) turned out to be another pyridine-forming catalyst 54]. A mechanism starting with partial oxidation of ethanol to acetaldehyde followed by aldolization, reaction with ammonia, cyclization and aromatization can be envisaged. An intriguing question is why pyridine is the main product and not methylpyridines (picolines). It has been suggested in this connection that zeolite radical sites induced Ci-species formation. 

Union Carbide Corp. developed a process using cyclohexanone as a principal intermediate and used this process commercially in 1966. According to the following reaction scheme, cyclohexanone is oxidized to caprolactone with peracetic acid, which is obtained by the reaction of acetaldehyde and hydrogen peroxide. The caprolactone is then converted to caprolactam by reaction with ammonia at high temperature and high pressure (process 5, Figure 2.11). The only by-product is acetic acid the amount of acetic acid obtained is about 1 kg/kg of product [123]. 

Acetaldehyde can be isolated and identified by the characteristic melting points of the crystalline compounds formed with hydrazines, semicarbazides, etc these derivatives of aldehydes can be separated by paper and column chromatography (104,113). Acetaldehyde has been separated quantitatively from other carbonyl compounds on an ion-exchange resin in the bisulfite form the aldehyde is then eluted from the column with a solution of sodium chloride (114). In larger quantities, acetaldehyde may be isolated by passing the vapor into ether, then saturating with dry ammonia acetaldehyde—ammonia crystallizes from the solution. Reactions with bisulfite, hydrazines, oximes, semicarb azides, and 5,5-dimethyl-1,3-cyclohexanedione [126-81 -8] (dimedone) have also been used to isolate acetaldehyde from various solutions. 

Halogens, See also Bromine (Br) Chlorine (Cl) Fluorine (F) Iodine (I) higher aliphatic alcohols, 2 5 in N-halamines, 13 98 reactions with acetaldehyde, 1 105 reactions with acetone, 1 163 reactions with acetylene, 1 180 reactions with alkanolamines from olefin oxides and ammonia, 2 125—126 reactions with aluminum, 2 284—285, 349-359... 

The general principle usually involves contact of an aldehyde or mixtures of aldehydes with ammonia at high temperature in the presence of an acidic catalyst. Aluminosilicate catalysts have been used (80USP4220783). A series of condensation reactions occurs with elimination of water and hydrogen and mixed products usually result. Acetaldehyde gives... 

In 1958, Ikekawa10 synthesized 2,7-naphthyridine and various substituted derivatives. His approach involved the reaction of 4-methylnicotinic acid with formaldehyde to afford the lactone 99 (R = H). The reaction of 99 with ammonia in methanol yields the amide (100) which, on oxidation with chromium trioxide, afforded 2,7-naphthyridin-l-one (101). This substance was converted into 2,7-naphthyridine (102, R = H) by consecutive treatment with phosphorus oxychloride, hydrazine, and copper sulfate. The 3-methyl derivative was similarly prepared starting with acetaldehyde. 

The iV-alkylation was considered to occur by the reaction of the carbonyl compounds, formed by the dehydrogenation of alcohols over the catalyst, with the hydrogenation products of pyridine,25 as suggested by Schwoegler and Adkins, who obtained good yields of /V-alkylpiperidines by the reaction of piperidine with alcohols.26 Maruoka et al. obtained a higher maximal yield of the iV-ethylated product in ethanol over Raney Co than over Raney Ni in the hydrogenation of 5-ethyl-2-methylpyridine (eq. 12.16),23 an alkylated pyridine prepared industrially by the reaction of acetaldehyde with ammonia. 

Reaction of ammonia with various combinations of aldehydes, over solid acid catalysts in the vapor phase, is a convenient route for producing pyridines [77]. For example, amination of a formaldehyde/acetaldehyde mixture affords pyridine and 3-picoline (Fig. 2.25). Mobil scientists found that MFI zeolites such as H-ZSM-5 were particularly effective for these reactions. 

A powerful oxidizer. Explosive reaction with acetaldehyde, acetic acid + heat, acetic anhydride + heat, benzaldehyde, benzene, benzylthylaniUne, butyraldehyde, 1,3-dimethylhexahydropyrimidone, diethyl ether, ethylacetate, isopropylacetate, methyl dioxane, pelargonic acid, pentyl acetate, phosphoms + heat, propionaldehyde, and other organic materials or solvents. Forms a friction- and heat-sensitive explosive mixture with potassium hexacyanoferrate. Ignites on contact with alcohols, acetic anhydride + tetrahydronaphthalene, acetone, butanol, chromium(II) sulfide, cyclohexanol, dimethyl formamide, ethanol, ethylene glycol, methanol, 2-propanol, pyridine. Violent reaction with acetic anhydride + 3-methylphenol (above 75°C), acetylene, bromine pentafluoride, glycerol, hexamethylphosphoramide, peroxyformic acid, selenium, sodium amide. Incandescent reaction with alkali metals (e.g., sodium, potassium), ammonia, arsenic, butyric acid (above 100°C), chlorine trifluoride, hydrogen sulfide + heat, sodium + heat, and sulfur. Incompatible with N,N-dimethylformamide. 

Another example is that of acetaldehyde, CH3—CHO. This compound as it will be recalled, (p. 116) forms addition products with several substances, e.g., hydrocyanic acid, ammonia andjsodium acid sulphite. The reaction with hydrocyanic acid is as follows ... 

F) Reaction of Lower Aldehydes with Ammonia. (1) Cool thoroughly 15 ml of ether in a small Erlenmeyer flask and add 1 ml of acetaldehyde. Saturate with dry ammonia. The tube leading ammonia into the aldehyde solution should be wide. Filter off the crystals. 

Carbothialdine" i.e. 4,6-dimethylperhydro-l,3,5-thiadiazine-2-thione, the reaction product of acetaldehyde with ammonia and carbon disulfide, has been known a long time (260, 288). Various structures have been proposed for it (83, 143, 164, 234). It was also known that this product may be obtained from acetaldehyde and ammonium dithiocarbamate and that two moles of aldehyde are necessary for the reaction. The reaction products of other aldehydes and amines had also been investigated with a view to elucidating their structure (31, 108). However, Ainley and co-workers (1) in 1944 were the first to determine the structure with certainty. The instability of "carbothialdines made it difficult to determine their structure by chemical means. It was by comparison of its U.V. spectrum with that of similar compounds such as (CCII) that the formula of perhydro-l,3,5-thiadiazine-2-thione (CCIV) was established, which accounts quite well for its properties. It is accepted... 

Pyridine bases such as 3-picoline and MEP are predominantly manufactured by the Chichibabin reaction, where a mixture of aldehydes or ketones is reacted with ammonia. Thus, formaldehyde, acetaldehyde and ammonia react in the gas phase to produce a mixture of pyridine and 3-picoline. By choosing the appropriate aldehyde or ketone, catalyst and phase (liquid or gas phase), the composition of the mixture can be varied at will, depending on the desired end-product. In the gas phase, silica alumina catalysts are often used, while in the liquid phase acid catalysts based on phosphoric or acetic acid are employed. In the 1990s, Reilly patented MET and BEA-based zeolite catalyst compositions for ammonia-aldehyde conversions to pyridine, picolines and alkyl pyridines. 

Picoline is obtained, typically in a 1 2 ratio along with the main product pyridine, by the gas-phase reaction of acetaldehyde, formaldehyde and ammonia. The lack of selectivity of this reaction to either pyridine or picoline has hitherto meant that the economy of the major product (pyridine) has determined the price and availability of picoline. Consequently, producers of pyridine have been able to control the quantity and prices of picoline on the market. This has led to the search for alternative feedstock and manufacturing processes for picoline. 

Takken (2) identified thiazoles and 3-thiazolines from the reaction of 2,3-butanedione and 2,3-pentanedione with ammonia, acetaldehyde and hydrogen sulfide at 20 °C. Study of tetramethylpyrazine (5) also showed that it can be readily formed in 3-hydroxy-2-butanone and ammonia model reaction at 22 C. Recent study of the model reaction of 3-hydroxy-2-butanone and ammonium acetate at low temperature revealed an interesting intermediate compound, 2-(l-hydroxyethyl)-2,3,4-trimethyl-3-oxazoline, along with 2,4,5-trimethyloxazole, 2,4,5-trimethyl-3-oxazoline, and tetramethylpyrazine were isolated and identified 4,5). We hypothesized that with the introducing of H2S, replacement of oxygen by sulfur could happen and sulfur-containing heterocyclic compoimds such as thiazoles and thiazolines could be formed along with oxazoles, oxazolines and pyrazines. 

---