Dehydrogenation of primary alcohols

Dehydrogenation of primary alcohols gives aldehydes, but in only moderate yield, but primary allylic alcohols are oxidized in high yield (80-95%). Secondary alcohols are also oxidized in high yield. The method, being neutral, is recommended for oxidation of substrates containing acid- or base-sensitive groups. 

Synthesis of secondary amides via the oxidative coupling (dehydrogenation) of primary alcohols R CH3(OH) and primary amines R (CH3)NH3 to the amides... 

The controlled oxidation or dehydrogenation of primary alcohols (Expts 5.74 to 5.76). 

Tishchenko (79), using a modified form of Raney nickel, obtained a 95.7 % yield of camphor from the dehydrogenation of borneol. Rutovskii, (80) received a 93.5% yield of camphor with Raney alloy. Reeves and Adkins (81), studying the dehydrogenation of primary alcohols, removed the hydrogen with ethylene. It was found that, though Raney nickel could be used for a catalyst for the reaction, the yields were low and, in general, the Raney nickel was inferior to a catalyst composed of copper, zinc, nickel, and barium chromite. 

Another commercial aldehyde synthesis is the catalytic dehydrogenation of primary alcohols at high temperature in the presence of a copper or a copper-chromite catalyst. Although there are several other synthetic processes employed, these tend to be smaller scale reactions. For example, acyl halides can be reduced to the aldehyde (Rosemnund reaction) using a palladium-on-barium sulfate catalyst. Formylation of aryl compounds, similar to hydrofomiylation, using HCN and HQ (Gatterman reaction) or carbon monoxide and HQ (Gatterman-Koch reaction) can be used to produce aromatic aldehydes. 

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]. 

Vapor-phase dehydrogenation of primary alcohols to aldehydes takes... 

These novel skeletal copper catalysts have significant potential for use in a wide range of organic synthesis reactions including those in which high caustic concentrations are involved such as in the dehydrogenation of primary alcohols to form carboxylic acid salts. 

The molecules of the substrate are oriented with their reacting groups to the surface of the catalyst. This is borne out by very near values of the activation energy of different compounds in reactions with equal indexes, for instance, in dehydrogenation of primary alcohols on copper [Constable 20), and others] and in the dehydration of normal primary alcohols on bauxites and on alumina, as well as by our recent studies (see Section I,D). 

Formula (11.58) contains a result of fundamental importance in catalytic reactions, unlike noncatalytic ones, the effect of substituents on the reaction rate and on E should be taken into account twice, viz., the effect on Qab and on Qak, the two effects being opposed. This explains, in particular, the results, which seemed contradictory, that in the homologous series, in some instances, the rate diminishes (this happens when SQab<8Qak), in other instances it increases (when Qab>Qak), and sometimes it does not change (when Qab = Qak). The last case is realized in the dehydrogenation of primary alcohols where e for normal primary alcohols from C2 to C9 has proved to be constant (on an oxide catalyst). In alcohol dehydration this compensation of Qab and Qak does not occur and a-, jS-, and y-substitution each introduces its increment into e. 

Bertoli M, Choualeb A, Gusev DG et al (2011) PNP pincer osmium polyhydrides for catalytic dehydrogenation of primary alcohols. Dalton Trans 40(35) 8941-8949... 

Several catalysts are available that effect the reduction of secondary alcohols to ketones. Typical acceptors are cyclohexene or various ketones.Diphen-ylacetylene has been used as an acceptor for dehydrogenation of primary alcohols. Attempts to activate alkanes in this way have been attempted and indeed... 

Ru(II) hydride complexes based on electron-rich PNP and PNN ligands of the type depicted on Fig. 13 (which can undergo aromatization/ dearomatization steps) efficiently and selectively catalyze the acceptorless dehydrogenation of primary alcohols to esters and H2 with high TONs... 

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