Dehydrogenation ethyl alcohol

Before dehydrogenation of ethane became the dominant method ethylene was pre pared by heating ethyl alcohol with sulfunc acid... 

The chemistry of ethyl alcohol is largely that of the hydroxyl group, namely, reactions of dehydration, dehydrogenation, oxidation, and esterification. The hydrogen atom of the hydroxyl group can be replaced by an active metal, such as sodium, potassium, and calcium, to form a metal ethoxide (ethylate) with the evolution of hydrogen gas (see Alkoxides, metal). 

Dehydrogenation. The dehydrogenation of ethyl alcohol to acetaldehyde can be effected by a vapor-phase reaction over various catalysts. 

The next stage leads to the transformation of the phosphorylated glyceric acid into pyruvic add, which is then converted into acetaldehyde and C02 by the enzyme carboxylase. As soon as the acetaldehyde is formed it enters into enzymic reaction with the phosphorylated glycer-aldehyde which is dehydrogenated to the acid while the aldehyde becomes ethyl alcohol. 

AcetaJdehyde is old. It is not ancient like ethyl alcohol, the essential ingredient in wine, but it owes its discovery to this closely related compound. Scheele first prepared acetaldehyde in 1774 by dehydrogenation of ethyl alcohol. Just as many nicknames get attached to people at infancy, this process generated the name aldehyde. It is a contraction for compounds that are alcohol dehydrogenates. 

CH. They are a dehydrogenated form of a corresponding alcohol. Formaldehyde, CH2O, corresponds to methanol, acetaldehyde, CH3CHO, to ethyl alcohol. 

It can be prepd also by dehydrogenation of butane in a one-step process or of ethyl alcohol in a two-step process(Ref 8). Other props methods of prepn are given in Beil(Ref 1)... 

The dehydrogenation of alcohols was first studied by Ipatieff, who obtained the corresponding aldehydes or ketones by treatment of methyl, ethyl, isopropyl, isobutyl, and isoamyl alcohols with such catalysts as a platinum tube, zinc rods, and brass at suitable temperatures. The work of Sabatier and Senderens and later Constable and Palmer added to the understanding of this industrially important reaction. 

A more recent process allows the manufacture of ethyl acetate from ethyl alcohol without the use of acetic acid or any other cofeedstocks. In the process (Fig. 1), ethyl alcohol is heated and passed through a catalytic dehydrogenation reactor where part of the ethyl alcohol is dehydrogenated to form ethyl acetate and hydrogen. 

Schwoegler and Adkins (93) reacted alcohols with primary and secondary amines over Raney nickel to form secondary and tertiary amines, respectively. Since tertiary alcohols do not undergo the reaction, it is assumed that the catalyst dehydrogenates the alcohol to a carbonyl compound which reacts with an amine to give a product that can be readily hydrogenated to a more complex amine. Piperidine was reacted with ethyl, n-butyl, and n-dodecyl alcohols to give 82, 70, and 69% yields, respectively, of the corresponding alkylpiperidines. 

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. 

Catalytic dehydrogenations of primary alcohols are achieved by passing vapors of the alcohols at 275-350 °C over a catalyst, usually supported on asbestos, silica gel, pumice, etc. Ethyl alcohol is converted into acetaldehyde in 88% yield at 93% conversion by passing it at 275 °C over a mixture of oxides of copper, cobalt, and chromium on asbestos [1135]. 

One mechanism that has been proposed for the conversion of ethyl alcohol to butadiene in the vapor phase consists of three steps (a) dehydration of the ethyl alcohol b) dehydrogenation of the ethyl alcohol (c) condensation of the ethylene and acetaldehyde in (a) and (b) to give butadiene, C Hg. At 400 . the following information is available for the three steps ... 

This evidence of reversibility in the acrolein-ethyl alcohol reaction at a temperature (396°, 1 atm.) where both allyl alcohol and ethyl alcohol are thermodynamically unstable with respect to the aldehydes and hydrogen indicated that the hydrogen transfer reaction was catalyzed by surfaces which were inactive for hydrogenation-dehydrogenation reactions. In order to explore the activity of magnesia and zinc oxide for hydrogenation, a number of these catalysts were tested for the direct hydrogenation of acrolein. 

Samarium is used to dope calcium fluoride crystals for use in optical masers or lasers. Compounds of the metal act as sensitizers for phosphors excited in the infrared the oxide exhibits catalytic properties in the dehydration and dehydrogenation of ethyl alcohol. It is used in infrared absorbing glass and as a neutron absorber in nuclear reactors. The metal is priced at about 3.50/g (99.9%). Little is known of the toxicity of samarium therefore, it should be handled carefully. 

H. Wieland (117) showed that dehydrogenation was the first stage in the enzymatic oxidation of organic molecules. Thus, palladium black catalyzed the oxidation of ethyl alcohol not only by oxygen but also anaerobically by quinone or methylene blue. The palladium black could be replaced by dehydrogenases, and the first step is clearly... 

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