Acetaldehyde trimerization

Paraldehyde (acetaldehyde trimer, 2,4,6-trimethyl-l,3,5-trioxane) 12,5 , 124 , d 0.995, n 1.407. Washed with water and fractionally distd. 

Aldehydes such as formaldehyde, acetaldehyde, paraformaldehyde, 1,3,5-trioxane, or acetaldehyde-trimer react with trimethyliodosilane (TIS) 17 to give 2,2-di-iodoethers such as 693 and 694 in up to 97% yield [205] (Scheme 5.66). 

We succeeded in showing that recycling of the enzyme was indeed possible in our IL solvent system, though the reaction rate gradually dropped with repetition of the reaction process. Since vinyl acetate was used as acyl donor, acetaldehyde was produced hy the hpase-catalyzed transesterification. It is well known that acetaldehyde acts as an inhibitor of enzymes because it forms a Schiff base with amino residue in the enzyme. However, due to the very volatile nature of acetaldehyde, it easily escapes from the reaction mixture and therefore has no inhibitory action on the lipase. However, this drop in reactivity was assumed to be caused by the inhibitory action of acetaldehyde oligomer which had accumulated in the [bmim][PFg] solvent system. In fact, it was confirmed that the reaction was inhibited by addition of acetaldehyde trimer. =... 

SYNS ACETALDEHYDE, TRIMER ELALDEHYDE PARACETALDEHYDE PAR. L PARALDEHYD (GERMAN) PARALDEIDE (ITALIAN) PCHO ... 

In a related protocol, the acetaldehyde trimer 54 from the generic RibA oligomerization was found to be a substrate for the N-acetylneuraminic acid aldolase (NeuA EC 4.1.3.3) which catalyzed the addition of pyruvate. By this means, a tetradeoxy-L-arahi o-2-nonulosonic acid 56 was obtained in 55% yield [116]. A one-pot, tandem operation was complicated by the fact that temperature requirements for optimum activity and stability of the two catalysts were not compatible. 

C]. Reacts violently with oxidizers. Capable of reacting as both a weak base and a weak acid. Decomposes on contact with acids, forming hydroxylamine and acetaldehyde. Forms explosive peroxides on contact with air, acids. Attacks various alkali metals (i.e., lithium, sodium, potassium, mbidium, cesium, francium). When exposed to air forms unstable peroxides may explode or decompose violently during distillation. ACETALDEHYDE TRIMER (123-63-7) see paraldehyde. 

ACETALDEHYDE TRIMER (123-63-7) Forms explosive mixture with air (flash point 62°F/17°C). Reacts with strong acids, caustics, ammonia, amines, oxidizers. Decomposes on contact with acids or acid fumes, forming acetaldehyde. Flow or agitation of substance may generate electrostatic charges due to low conductivity. 

Beilstein Handbook Reference) Acetaldehyde, trimer p-Acetaldehyde AI3-03115 BRN 0080142 DEA No. 2585 EINECS 204-639-8 Elaldehyde HSDB 3375 NSC 9799 Paracetaldehyde Paral Paraldehyd Paraldehyde Paraldehyde Draught (BPC 1973) Paraldehyde Enema (BPC 1973) Paraldeide RCRA waste number U182 1,3,5-Trimethyl-2,4,6-trioxane 2,4,6-Trimethyl-1,3,5-trioxane 2,4,6-T rimethyl-1,3,5-trioxaoyolohexane ... 

Paraldehyde (acetaldehyde trimer, 2r,4c,6c-trimethyl-l,3,5-trioxane, all-cis) [123-63-7] M 132.2, m 12.5°, b 124°/751mm, d4 0.995, hd 1.407. Wash paraldehyde with water and fractionally distil it. Alternatively, it is purified by diying with anhydrous Na2S04, then cooled to 5°, and the frozen material is separated by decantatioa The solid is distilled (b 121-124°/atm), the distillate is collected, stored over anhydrous Na2S04 for several days and re-distilled at atmospheric pressure before use [Le Fevre et al. J Chem Soc 290 1950]. The 2r,4c,6t-trimethyl-l,3,5-trioxane has m 14.5°, b 125°/760mm. [Beilstein 19 II 394, 19 III/IV 4715.19/9 V 112.]... 

Acetaldehyde, trimer. See Paraldehyde Specialty Chemicals Source Book-Third Edition... 

Synonyms Acetaldehyde, trimer Elaldehyde Paraacetaldehyde Paracetaldehyde Paral PCHO 2,4,6-Trimethyl-1,3,5-trioxacyclohexane 2,4,6-Trimethyl-1,3,5-trioxane 2,4,6-Trimethyl-s-trioxane s-Trimethyltrioxymethylene Empirical C6H12O3... 

Polymerization. Paraldehyde, 2,4,6-trimethyl-1,3-5-trioxane [123-63-7] a cycHc trimer of acetaldehyde, is formed when a mineral acid, such as sulfuric, phosphoric, or hydrochloric acid, is added to acetaldehyde (45). Paraldehyde can also be formed continuously by feeding Hquid acetaldehyde at 15—20°C over an acid ion-exchange resin (46). Depolymerization of paraldehyde occurs in the presence of acid catalysts (47) after neutralization with sodium acetate, acetaldehyde and paraldehyde are recovered by distillation. Paraldehyde is a colorless Hquid, boiling at 125.35°C at 101 kPa (1 atm). 

Miscellaneous Reactions. Sodium bisulfite adds to acetaldehyde to form a white crystalline addition compound, insoluble in ethyl alcohol and ether. This bisulfite addition compound is frequendy used to isolate and purify acetaldehyde, which may be regenerated with dilute acid. Hydrocyanic acid adds to acetaldehyde in the presence of an alkaU catalyst to form cyanohydrin the cyanohydrin may also be prepared from sodium cyanide and the bisulfite addition compound. Acrylonittile [107-13-1] (qv) can be made from acetaldehyde and hydrocyanic acid by heating the cyanohydrin that is formed to 600—700°C (77). Alanine [302-72-7] can be prepared by the reaction of an ammonium salt and an alkaU metal cyanide with acetaldehyde this is a general method for the preparation of a-amino acids called the Strecker amino acids synthesis. Grignard reagents add readily to acetaldehyde, the final product being a secondary alcohol. Thioacetaldehyde [2765-04-0] is formed by reaction of acetaldehyde with hydrogen sulfide thioacetaldehyde polymerizes readily to the trimer. 

Primary aromatic amines react with aldehydes to form Schiff bases. Schiff bases formed from the reaction of lower aUphatic aldehydes, such as formaldehyde and acetaldehyde, with primary aromatic amines are often unstable and polymerize readily. Aniline reacts with formaldehyde in aqueous acid solutions to yield mixtures of a crystalline trimer of the Schiff base, methylenedianilines, and polymers. Reaction of aniline hydrochloride and formaldehyde also yields polymeric products and under certain conditions, the predominant product is 4,4 -methylenedianiline [101 -77-9] (26), an important intermediate for 4,4 -methylenebis(phenyhsocyanate) [101-68-8], or MDI (see Amines, aromatic amines, l thylenedianiline). 

Acetaldehyde ammonia trimer (hexahydro-2,4,6-trimethyl-l,3,5-triazine trihydrate) [76231-37-3] M 183.3, m 94-96 , 95-97 , 97 , b 110 (partly dec). Crystd from EtOH-Et20. When prepared it separates as the trihydrate which can be dried in a vacuum over CaCl2 at room temp to give the anhydrous compound with the same melting point. The dihydrate melts at 25-28° then resolidifies and melts again at 94-95°. IRRITATES THE EYES AND MUCOUS MEMBRANES. [J Org Chem 38 3288 1973.]... 

The monomer (laurolactam) could he produced from 1,5,9-cyclododeca-triene, a trimer of hutadiene (Chapter 9). The trimer is epoxidized with peracetic acid or acetaldehyde peracetate and then hydrogenated. The saturated epoxide is rearranged to the ketone with Mgl2 at 100°C. is then changed to the oxime and rearranged to laurolactam. 

When catalyzed by acids, low molecular weight aldehydes add to each other to give cyclic acetals, the most common product being the trimer. The cyclic trimer of formaldehyde is called trioxane, and that of acetaldehyde is known as paraldehyde. Under certain conditions, it is possible to get tetramers or dimers. Aldehydes can also polymerize to linear polymers, but here a small amount of water is required to form hemiacetal groups at the ends of the chains. The linear polymer formed from formaldehyde is called paraformaldehyde. Since trimers and polymers of aldehydes are acetals, they are stable to bases but can be hydrolyzed by acids. Because formaldehyde and acetaldehyde have low boiling points, it is often convenient to use them in the form of their trimers or polymers. 

For the solubility of TPA in prepolymer, no data are available and the polymer-solvent interaction parameter X of the Flory-Huggins relationship is not accurately known. No experimental data are available for the vapour pressures of dimer or trimer. The published values for the diffusion coefficient of EG in solid and molten PET vary by orders of magnitude. For the diffusion of water, acetaldehyde and DEG in polymer, no reliable data are available. It is not even agreed upon if the mutual diffusion coefficients depend on the polymer molecular weight or on the melt viscosity, and if they are linear or exponential functions of temperature. Molecular modelling, accompanied by the rapid growth of computer performance, will hopefully help to solve this problem in the near future. The mass-transfer mechanisms for by-products in solid PET are not established, and the dependency of the solid-state polycondensation rate on crystallinity is still a matter of assumptions. 

Chemical/Physical. Oxidation in air yields acetic acid (Windholz et ah, 1983). In the presence of sulfuric, hydrochloric, or phosphoric acids, polymerizes explosively forming trimeric paraldehyde (Huntress and Mulliken, 1941 Patnaik, 1992). In an aqueous solution at 25 °C, acetaldehyde is partially hydrated, i.e., 0.60 expressed as a mole fraction, forming a gem-diol (Bell and McDougall, 1960). Acetaldehyde decomposes at temperatures greater than 400 °C, forming carbon monoxide and methane (Patnaik, 1992). 

Nicotinic acid Nicotinic acid, pyridine-3-carboxylic acid (20.2.9) is synthesized industrially by heating a paraldehyde trimer of acetaldehyde, under pressure with ammonia, which leads to the formation of 2-methyl-5-ethylpyridine, followed by oxidation with nitric acid which gives the desired product [22-25]. 

Monitoring of acetaldehyde-induced polymerization of catechin and epicatechin by HPLC-MS demonstrated the formation of several methylmethine-linked flavanol dimers, trimers, and tetramers. Detection of the intermediate ethanol adducts confirmed the mechanism postulated by Timberlake and Bridle, which involves protonation of acetaldehyde in the acidic medium, followed by nucleophilic attack of the resulting carbocation by the flavan unit. The ethanol adduct then loses a water molecule and gives a new carbocation that undergoes nucleophilic attack by another flavanol molecule. Four dimers (C6-C6, C8-C8, and C6-C8, R and S) were formed from each monomeric flavanol. When both epicatechin and catechin units were present, additional isomers containing both types of units were... 

In 1972, Eiter and his group reported the synthesis of a-alkoxy dialkyl N-nitrosamines (11),which can be obtained easily in 20-50 g quantities. This synthetic scheme works well when formaldehyde was used. In those cases when higher aliphatic aldehydes are used (e.g. acetaldehyde), the yields decreased to 3-5%. The a -alkoxy dialkyInitrosamines always contained the trimeric paraldehyde as impurity. When acetaldehyde and... 

Trimerization of aldehydes affords trialkyl-1,3,5-thioxanes 11. Compounds of this type were obtained from acetaldehyde, propionaldehyde (29,33), isobutyraldehyde (47), and isovaleralde-hyde (35). The two isomers normally formed can be separated by GC. 

Secondary amines are less selectively converted than primary amines. With diethyl-amine 46% acetonitrile, 3% acetaldehyde and 36% acetic acid are obtained with pyrrolidine 50% of the trimer of 3,4-dihydro-2 H-pyrrole are formed 2. In our hands controlled potential electrolysis (0.39 V vs. SCE) of pyrrolidine formed... 

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