Acetaldehyde chemical intermediate

Ethanol s many uses can be conveniently divided into solvent and chemical uses. As a solvent, ethanol dissolves many organic-based materials such as fats, oils, and hydrocarbons. As a chemical intermediate, ethanol is a precursor for acetaldehyde, acetic acid, and diethyl ether, and it is used in the manufacture of glycol ethyl ethers, ethylamines, and many ethyl esters. 

Uses. Nearly half the ethyl alcohol produced in petrochemical plants (not the stuff fermented for human consumption) is used as a chemical intermediate in the manufacture of ethyl acrylate, ethyl amines, ethyl acetate (when you pop the cap on nail polish remover, you smell ethyl acetate), ethylene chloride, glycol ethers, acetaldehyde, and acetic acid. However, you will see in the chapters on acetaldehyde and acetic acid, there are now more competitive routes than those based on ethyl alcohol. 

Ethanol s use as a chemical intermediate (Table 8) suffered considerably from its replacement in the production of acetaldehyde, butyraldehyde, acetic acid, and ethylhexanol. The switch from the ethanol route to those products has depressed demand for ethanol by more than 300 x 106 L (80 x 106 gal) since 1970. This decrease reflects newer technologies for the manufacture of acetaldehyde and acetic acid, which is the largest use for acetaldehyde, by direct routes using ethylene, butane (173), and methanol. Oxo processes (qv) such as Union Carbide s Low Pressure Oxo process for the production of butanol and ethylhexanol have totally replaced the processes based on acetaldehyde. For example, U.S. consumption of ethanol for acetaldehyde manufacture declined steadily from 50% in 1962 to 37% in 1964 and none in 1990. Butadiene was made from ethanol on a large scale during Wodd War II, but this route is no longer competitive with butadiene derived from petroleum operations. 

Platform chemicals are compounds that serve as building blocks for numerous chemical intermediates and end products. An example is ethylene, which serves as the feedstock for derivatives such as acetaldehyde, ethylene dichloride, ethylene oxide, polyethylene, vinyl acetate, and ethyl acetate. Biobased chemicals such as succinic acid, 3-hydroxypropionic acid (3-HP), and butanol also have the potential to be converted into multiple derivatives, some of which are commodity chemicals and others that are higher-value chemicals. 

Aldehydes find die most widespread use as chemical intermediates. The production of acetaldehyde, propionaldehyde, and butyraldehyde as precursors of the corresponding alcohols and acids are examples. The aldehydes of low molecular weight are also condensed in an aldol reaction to form derivatives which are important intermediates for the plasticizer industry (see Plasticizers). As mentioned earlier, 2-etliylliexanol, produced from butyraldehyde, is used in the manufacture of di(2-ethylhexyl) phthalate [117-87-7]. Aldehydes are also used as intermediates for the manufacture of solvents (alcohols and ethers), resins, and dyes. Isobutyraldehyde is used as an intermediate for production of primary solvents and rubber antioxidants (see Antioxidants). Fatty aldehydes Cg—C13 are used in nearly all perfume types and aromas (see Perfumes). Polymers and copolymers of aldehydes exist and are of commercial significance. 

Acetoxylations (oxyacylations) have to be seen in context with olefin oxidation to carbonyl compounds (Wacker process, Section 2.4.1). With the lowest olefin, ethylene, acetaldehyde is formed. In water-free acetic acid no reaction takes place. Only in the presence of alkali acetates - the acetate ion shows higher nu-cleophilicity than acetic acid - ethylene reacts with palladium salts (eq. (1)) to give vinyl acetate, the expected product, as first reported by Moiseev et al. [1]. Stem and Spector [2] independently used [HP04] as base in a mixture of isooctane and acetic acid. This reaction could be exploited for a commercial process to produce vinyl acetate and closed the last gap replacing acetylene by the cheaper ethylene, a petrochemical feed material, for the production of large-tonnage chemical intermediates. 

Acetaldehyde is a versatile chemical intermediate. It is commercially made via the Wacker process, the partial oxidation of ethylene. That process is very corrosive, requiring expensive materials of construction. And like all oxidations, over-oxidation of the ingredient and the product reduce the 5deld, and convert expensive ethylene into carbon oxides. 

This vinyl ether is monomeric in character and is used as a chemical intermediate or os o crosslinking ogent. Addition of isocyanic acid produces secondary diisocyonates. Divinyl ethers hydrolyze to the glycol and acetaldehyde. Chlorine or bromine odd to the double bonds. Reaction with an alcohol in the presence of water produces a diacetal. Polymerization of divinyl ether of diethylene glycol with acidic catolysts produce crasslinked gels. Unsoturoted polyesters, crosslinked with styrene, hove been made noncorrosive to metols through use of divinyl ethers to reduce hydroxyl ond acid numbeis. 

The one- and two-carbon aldehydes, formaldehyde and acetaldehyde, are gaseous products at ambient temperatures. Formaldehyde boils at -2PC while acetaldehyde boils at 20 C. Formaldehyde is most often used as a 37-55 wt% aqueous solution or as an alcoholic solution containing some 55 wt% formaldehyde. Methanol and n-butanol are the two alcohols often used for the formaldehyde solutions. Other aliphatic aldehydes useful as chemical intermediates include propionaldehyde (b.p. 48 C) and two butyl aldehydes, rt-butyraldehyde (b.p. 75"C) and isobutyraldehyde (b.p. 64"C). The one commercially important heterocyclic aldehyde, furfural, is a high boiling-point (161.7 0 liquid. 

Acetaldehyde is an intermediate for many chemicals such as acetic acid, n-butanol, pentaerithritol, and polyacetaldehyde. 

The close chemical relationship between acetaldehyde and ethyl alcohol is apparent in the grape fermentation process. The sugar in the grapes turns to acetaldehyde as an intermediate step. Fortunately for wine makers and oenophiles, the acetaldehyde immediately reduces to ethyl alcohol. 

As early as World War I, acetaldehyde was the primary route to acetic acid and acetone. While other preferred technologies for acetone have been developed, acetaldehyde remains an important intermediate to acetic acid as well as several other chemicals. 

The generation of the (2S,3R) diol 4 from 1 is the consequence of a multlenzymic process involving two distinct chemical operations (2) (i) Addition of a unit equivalent to acetaldehyde onto thesiface of the carbonyl carbon atom of the unsaturated aldehyde to form a (3R) -hydroxyketone, in an acyloin of type condensation, and (ii) reduction of the latter intermediate on the face of the carbonyl group to give rise to the diol actually isolated (Eq. 2). 

Students may have seen the acetaldehyde decomposition reaction system described as an example of the application of the pseudo steady state (PSS), which is usually covered in courses in chemical kinetics. We dealt with this assumption in Chapter 4 (along with the equilibrium step assumption) in the section on approximate methods for handling multiple reaction systems. In this approximation one tries to approximate a set of reactions by a simpler single reaction by invoking the pseudo steady state on suitable intermediate species. 

Acetaldehyde is a natural product of combustion and photo-oxidation of hydrocarbons commonly found in the atmosphere. It is an important industrial chemical and may be released into the air or in wastewater during its production and use. It has been detected at low levels in drinking-water, surface water, rainwater, effluents, engine exhaust and ambient and indoor air samples. It is also photochemically produced in surface water. Acetaldehyde is an intermediate product in the metabolism of ethanol and sugars and therefore occurs in trace quantities in human blood. It is present in small amounts in all alcoholic beverages, such as beer, wine and spirits and in plant juices and essential oils, roasted coffee and tobacco smoke (lira et al., 1985 Hagemeyer, 1991 United States National Library of Medicine, 1998). 

It has been used as a solvent and as an intermediate in the manuf of chemicals used in the expl industry and of synthetic rubber (Ref 4). During WWII, acetal(as well as acetaldehyde) was used in Germany as hyper-gollic fuel in liquid rocket propellants in conjunction with red or white fuming nitric acid which served as an oxidizer. Acetal was later replaced by ca te ch o 1( Bren zc ate chin or Brenzol in Ger)(Ref 10)... 

However, in their study of intermediates in the enzymic reduction of acetaldehyde, Shore and Gutfreund could find no inequivalence in the binding sites of the subunits at all NADH concentrations studied.1369 This conclusion that the two active sites are kinetically equivalent is supported by kinetic studies by Hadom et al.1370 and by Kvassman and Pettersson. 1 Work by Kordal and Parsons also supports this conclusion.13" They devised a method of persuading 3H-labelled NADH to bind to one site per enzyme molecule and then, using a stopped-flow technique, to react this with excess unlabelled product. Full site reactivity was observed in either direction. They concluded that no half site reactivity was observed, and that there was no indication of subunit asymmetry induced by either the coenzyme binding or by chemical reaction. 

Intermediates of this type have the necessary chemical reactivity for cleaving the bonds indicated in figure 10.1b and c. The decarboxylated product of the pyruvate adduct shown in equation (2) is resonance-stabilized by the thiazolium ring (fig. 10.2a). This intermediate may be protonated to a-hydroxyethyl thiamine pyrophosphate (fig. I0.2d) alternatively, it may react with other electrophiles, such as the carbonyl groups of acetaldehyde or pyruvate, to form the species in figure 10.2b and c or it may be oxidized to acetyl-thiamine pyrophosphate (fig. 10.2e). The fate of the intermediate depends on the reaction specificity of the enzyme with which the coenzyme is associated. 

First steps to elucidate the reaction mechanism of PDC were achieved by the investigation of model reactions using ThDP or thiamine [36,37], Besides the identification of C2-ThDP as the catalytic center of the cofactor [36], the mechanism of the ThDP-catalyzed decarboxylation of a-keto acids as well as the formation of acyloins was explained by the formation of a common reaction intermediate, active acetaldehyde . This active species was first identified as HEThDP 7 (Scheme 3) [38,39]. Later studies revealed the a-carbanion/enamine 6 as the most likely candidate for the active acetaldehyde [40 47] (for a comprehensive review see [48]). The relevance of different functional groups in the ThDP-molecule for the enzymatic catalysis was elucidated by site-directed substitutions of the cofactor ThDP by chemical means (for a review see... 

Acetaldehyde is an intermediate in acetic acid and vinyl acetate production. Since 1916 it has been produced from the addition of water to acetylene, a reaction catalyzed by divalent mercury in sulphuric acid (20%)/water. Acetylene was made from coal. In Germany in particular, a lot of research was carried out on the use of acetylene as a chemical feedstock. 

EA [Ethyl Acetate] A one-step process for converting ethanol to ethyl acetate. Acetaldehyde is an intermediate, and the catalyst is proprietary. Developed by Davy Process Technology and Sasol from 2000, following initial work by Davy in 1983. The first commercial plant was built by Sasol in Secunda, South Africa, in 2001. The process won the Kirkpatrick Honor Award for Chemical Engineering Achievement in 2003. 

The synthesis of acetaldehyde by oxidation of ethylene, generally known as the Wacker process, was a major landmark in the application of homogeneous catalysis to industrial organic chemistry. It was also a major step in the displacement of acetylene (made from calcium carbide) as the feedstock for the manufacture of organic chemicals. Acetylene-based acetaldehyde was a major intermediate for production of acetic acid and butyraldehyde. However the cost was high because a large energy input is required to produce acetylene. The acetylene process still survives in a few East European countries and in Switzerland, where low cost acetylene is available. 

Acrylonitrile and methacrylonitrile can be obtained from petro-chemical olefins [2] by the noncatalytic reactions of HCN with acetaldehyde, acetone (cyanohydrin is the intermediate in these processes) or oxiranes (Z-cyanoetltanol being the intermediate in the acrylonitrile synthesis from ethylene oxide). 

When cyanocuprate 5 is added to bornanesultam 3, and the intermediate addition product is trapped with acetaldehyde, the / -amino-/J -hydroxy acid derivative 6 is obtained, after protection of the hydroxy group, in 71% overall yield and 99% de. No other diastereomers are detected 132. The stereochemistry of 6 is established by further chemical conversion to a -lactam of known absolute configuration. 

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