Acetaldehyde hydrate formed from

This can be illustrated by comparing the amount of hydrate formed from formaldehyde, acetaldehyde, and acetone. 

The Hydrate and Enol Form. In aqueous solutions, acetaldehyde exists in equihbrium with the acetaldehyde hydrate [4433-56-17, (CH2CH(0H)2). The degree of hydration can be computed from an equation derived by BeU and Clunie (31). Hydration, the mean heat of which is —21.34 kJ/mol (—89.29 kcal/mol), has been attributed to hyperconjugation (32). The enol form, vinyl alcohol [557-75-5] (CH2=CHOH) exists in equihbrium with acetaldehyde to the extent of approximately 1 molecule per 30,000. Acetaldehyde enol has been acetylated with ketene [463-51-4] to form vinyl acetate [108-05-4] (33). 

For example, Figure 2.3 shows plots of the a constants of X vs. log p/T of aliphatic carboxylic acids (XCOaH) and vs. log k for the dehydration of acetaldehyde hydrate by XC02H. Deviations from Equations 2.18 and 2.19 occurwhen the rate of reaction or position of equilibrium becomes dependent on steric factors. For example, Taft studied the enthalpies of dissociation, A Hd, of the addition compounds formed between boron trimethyl and amines (X1X2X3N) and found that when the amine is ammonia or a straight-chain primary amine the dissociation conforms to Equation 2.20, in which 2 ° is the sum of the a values for the... 

The slope of the plot of log/cnA versus pA a is the same as that against -logAgq, because p/fns is constant and independent of the acid (HA). This relationship is very important as it is often very difficult to measure an equilibrium constant explicitly and changes would be even more difficult to determine accurately. It is usually a simple matter to determine dissociation constants accurately and moreover there are large databases of measured pAS, values in existence. The equilibria (Equations 31-33) sum to give the equilibrium of the initially formed intermediate (MeCHOH ) from HA and acetaldehyde hydrate. 

Acetaldehyde may also mediate the self-condensation of anthocyanins, leading to the formation of oligomeric methylmethine-linked anthocyanins (Atanasova et al, 2002b Salas et al, 2005). These adducts are described to possess a (525 nm) hypsochromi-cally shifted from that of mvSglc (530 nm), as obtained by LC-DAD, and to have one of the anthocyanin moieties of the dimer mv3glc-HC(CH3)-mv3glc in their hydrated form at wine pH (Salas et al, 2005). 

Since 1960, the Hquid-phase oxidation of ethylene has been the process of choice for the manufacture of acetaldehyde. There is, however, stiU some commercial production by the partial oxidation of ethyl alcohol and hydration of acetylene. The economics of the various processes are strongly dependent on the prices of the feedstocks. Acetaldehyde is also formed as a coproduct in the high temperature oxidation of butane. A more recently developed rhodium catalyzed process produces acetaldehyde from synthesis gas as a coproduct with ethyl alcohol and acetic acid (83—94). 

Acetaldehyde to Acetic Acid. The formation of acetic acid furnishes an excellent example of liquid-phase oxidation with molecular oxygen. Acetic acid may be obtained by the direct oxidation of ethanol, but the concentrated acid is generally obtained by oxidation methods from acetaldehyde that may have been formed by the hydration of acetylene or the oxidation of ethanol. The oxidation usually occurs in acetic acid solution in the presence of a catalyst and at atmospheric or elevated pressures. Temperatures may range up to lOO C, depending upon conditions, but are usually lower. 

The cis and trans forms of the enols from the (diethoxyphosphinoyl)acetaldehydes (EtO)2P(0)CHRCHO (R = Me or Ph) have been isolated as pure lithium complexes. Although the mono- and di-chloro derivatives of (diethoxyphosphinoyl)acetaJdehyde have been obtained, in the past, by a direct chlorination step, an alternative route has now been proposed which involves, as the initial step, the chlorination of a dialkyl (2-ethoxyethenyl)phosphonate in an aqueous medium this results in the formation of the aldehyde hydrate (169). Yet a further veu iation consists in the chlorination of a dialkyl... 

This reaction was first reported by Fittig and Schrohe in 1875 and subsequently extended by Kutscheroff in 1881. It is an acid-catalyzed hydration of alkynes into ketones. In this reaction, dilute sulfuric acid and mercuric salt are used as catalysts, and mercuric chloride can form a complex with acetylene in aqueous solution. This reaction has been used to prepare ketones from higher alkynes, such as propyne, and vinylacetylene as well as in commercial production of acetaldehyde from acetylene. ... 

Apart from its use in drinks, alcohol is used as a solvent and to form ethanal (acetaldehyde). Formerly, the main source was by fermentation of molasses, but now catalytic hydration of ethene is used to manufacture industrial ethanol. 

The hydrolysis of carbohydrates in dodecylbenzene sulphonic acid in dioxane-water mixtures has been the subject of one study in which it Was found that the hydrolysis was accelerated by about 21 times in dioxane mixtures above 60% by volume [126], but no coherent mechanism was put forward for the catalysis. Non-ionic surfactants may form inverse micelles in non-aqueous solvents in the presence of small amounts of water. Triton X-1(X), for example, micellizes in carbon tetrachloride on addition of water. This system, which obviously does not suffer the problems which result from the dissociation of the head groups of ionic surfactants in the water pool, has been used to investigate the hydration reaction of acetaldehyde [127]. This acid-catalysed reaction is increased by a factor of 10000 over that in water (Table 11.9). In spite of the nonionic nature of the peripheral head groups surrounding and penetrating the aqueous core, the nature of the water is such that ionization of solubilized species is changed. 

Glycidyl ethers were identified in the form of derivatives (2,4-di-nitrophenylhydrazones) of corresponding substituted acetaldehydes (alkoxy or acyloxyacetaldehydes) obtained from parent ethers by hydration and oxidation with HIO4 (12). 

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