Acetaldehyde , from ethyl alcohol

This column must be capable of separating acetaldehyde from ethyl alcohol with the greatest completeness. A very efficient type is that of Hahn,2 in which the column is kept at a constant temperature by means of boiling methyl alcohol in a central tube, the vapors passing up an outer annular space. It is necessary that the lower part of the condenser employed be sufficiently broad (say 2 cm. in diameter) so that when in... 

Sodium hypobromite and sodium hypoiodite solutions react in an analogous manner and yield bromoform (CHBrj) and iodoform (CHI,) respectively. The smooth production of the trihalomethanes by the use of the appropriate hypohalides is termed the haloform reaction. It is applicable to all compounds containing the —COCH3 group or which yield a substance containing this group by oxidation (e.gr., acetaldehyde from ethyl alcohol). Iodoform is a stable, crystalline, yellow solid, m.p. 119°, with a characteristic odour it is only sparingly soluble in water and hence will separate, even in very minute quantity, from an aqueous solution and can easUy be identified by m.p. and mixed m.p. determinations. 

In the examples so far given, the application of the theory may be stated to be little more than an interesting hypothesis as to the disposition of atoms on a surface prior to and during reaction. It does not, for instance, enable it to be decided why a particular duplet should favor formation of acetaldehyde from ethyl alcohol, and another duplet, formation of ethylene. It would not appear that the intemuclear distances of the two types of duplet would be different, while the fact that both... 

From Ethyl Alcohol. Some acetaldehyde is produced commercially by the catalytic oxidation of ethyl alcohol. The oxidation is carried out by passing alcohol vapors and preheated air over a silver catalyst at 480°C (98). 

Alcohol to acetic acid Aldehydes to alcohols (e.g., acetaldehyde to ethyl alcohol) Starch to glucose Hexose phosphate from hexose and phosphoric acid... 

Commercially, these acids are produced in several ways (I) oxidation of relevant alcohol—e.g.. acetic acid from ethyl alcohol (2) oxidation of relevant aldehyde—e g. acetic acid from acetaldehyde (3) bacterial... 

A considerable wood hydrolysis industry with rather old traditions is located in the Soviet Union. The main fermentation product based on hexoses in wood hydrolyzates is ethyl alcohol, but pentoses and aliphatic acids can also be utilized in the production of proteins (see Section 10.2.3). A variety of chemicals, including ethylene, ethylene oxide, acetaldehyde, and acetic acid, can be produced from ethyl alcohol. One interesting future application of ethyl alcohol concerns its use as a motor fuel mixed with gasoline (gasohol). 

Acetaldehyde, CH3CHO, is a similar substance made from ethyl alcohol. 

Once-through conversion is 45 to 50 per cent and yields are 94 to 96 molar per cent Unreacted ethanol and the acetaldehyde produced are extracted from the gases leaving the reactor by scrubbing with cold aqueous etbanoL The acetaldehyde and ethyl alcohol are separated by distillation, and the dilute ethanol is concentrated and recycled. 

It was originally thought that some OH radicals must abstract hydrogen atoms from ethylene to form C2H3 radicals (14), but it is now concluded that all OH radicals add to ethylene (Reaction 1) and that the -hydroxy-ethyl radicals enter into reactions, not all of which give rise to acetaldehyde (13). Other recent evidence also supports this view (4). The absorption spectrum of the -hydroxyethyl radicals is similar to that of the a-hydroxyethyl radicals which can be prepared from ethyl alcohol (13). 

The saponification of 0 labeled ethyl propanoate was desenbed in Section 20 11 as one of the significant expenments that demonstrated acyl-oxygen cleavage in ester hydrolysis The 0 labeled ethyl propanoate used in this expenment was prepared from 0 labeled ethyl alcohol which in turn was obtained from acetaldehyde and 0 enriched water Wnte a senes of equations... 

Acetaldehyde [75-07-0] (ethanal), CH CHO, was first prepared by Scheele ia 1774, by the action of manganese dioxide [1313-13-9] and sulfuric acid [7664-93-9] on ethanol [64-17-5]. The stmcture of acetaldehyde was estabhshed in 1835 by Liebig from a pure sample prepared by oxidising ethyl alcohol with chromic acid. Liebig named the compound "aldehyde" from the Latin words translated as al(cohol) dehyd(rogenated). The formation of acetaldehyde by the addition of water [7732-18-5] to acetylene [74-86-2] was observed by Kutscherow] in 1881. 

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. 

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). 

Other synthetic methods have been investigated but have not become commercial. These include, for example, the hydration of ethylene in the presence of dilute acids (weak sulfuric acid process) the conversion of acetylene to acetaldehyde, followed by hydrogenation of the aldehyde to ethyl alcohol and the Fischer-Tropsch hydrocarbon synthesis. Synthetic fuels research has resulted in a whole new look at processes to make lower molecular weight alcohols from synthesis gas. 

The conversion of ethyl alcohol by way of acetaldehyde into acetic acid is the chemical expression equivalent to acetic fermentation. In this process the acetic bacteria utilise atmospheric oxygen in order to bind the hydrogen. That the hydrogen which has to be removed is activated, and not the oxygen (as was formerly thought), is shown by experiments in which oxygen is eaxluded and replaced by quinone the bacteria produce acetic acid from alcohol as before and the quinone is reduced to hydroquinone. 

In the mid-l O s, it was found that acetic acid itself could be catalytically dehydrated to ketene, which when absorbed in fresh acid gave the anhydride. Soon after this process became commercially established, the older processes of making the anhydride were discontinued. By this time synthetic acetic acid was being made from acetylene via acetaldehyde oxidation, from synthetic ethyl alcohol also via acetaldehyde, and by the direct oxidation of fermentation ethyl alcohol. The ketene route to acetic anhydride, in addition to starting from acetic acid, later employed acetone as raw material. 

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