Condensation of alcohols

Ethyl chloride can be dehydrochlorinated to ethylene using alcohoHc potash. Condensation of alcohol with ethyl chloride in this reaction also produces some diethyl ether. Heating to 625°C and subsequent contact with calcium oxide and water at 400—450°C gives ethyl alcohol as the chief product of decomposition. Ethyl chloride yields butane, ethylene, water, and a soHd of unknown composition when heated with metallic magnesium for about six hours in a sealed tube. Ethyl chloride forms regular crystals of a hydrate with water at 0°C (5). Dry ethyl chloride can be used in contact with most common metals in the absence of air up to 200°C. Its oxidation and hydrolysis are slow at ordinary temperatures. Ethyl chloride yields ethyl alcohol, acetaldehyde, and some ethylene in the presence of steam with various catalysts, eg, titanium dioxide and barium chloride. 

This direct condensation of alcohols has limited use as a route to polymers because many alcohols undergo other reactions under the conditions required for condensation. Nature forges ether linkages in a more roundabout way than by eliminating water directly. The most important pol Tners containing ether linkages are two biochemical macromolecules, starch and cellulose. 

The Guerbet reaction is an important industrial process for increasing the carbon numbers of alcohols. Thus, a primary or secondary alcohol reacts with itself or another alcohol to produce a higher alcohol (Scheme 23). Alkaline earth metal oxides have been used as catalysts for the condensation of alcohols. Ueda et al. (158,159) reported the condensation of methanol with other primary or secondary alcohols having a methyl or methylene group at the )S-position they used MgO, CaO, and ZnO as catalysts. The reactions were performed with gas-phase reactants at 635 K only MgO was found to be both active and selective (>80%). 

A. Condensation of Alcohols with Substituted Olefins and Acetylenes to Give... 

Apart from halides, pseudohalides and acetates, FeCl3 is able to activate hydroxyl groups in a similar manner. Hence various substitutions of hydroxyl groups have been developed, e.g. the condensation of alcohols or phenols with diphenylmethanol to give DPM-protected alcohols [Equation (7.4), Scheme 7.11] [15] or the direct coupling of allylic or benzylic alcohols with C—H-acidic compounds [Equation (7.5)] [16]. 

Rychnovsky et al. have postulated the same mechanism during their study of the a-acetoxy acetal 143 cyclization and of the condensation of alcohol 145 with cin-namyl aldehyde (Scheme 13.49) [72-74]. In both cases, the desired adducts 144a,b were obtained in good yields and excellent diastereoselectivity. 

The most general method for the synthesis of tetrahydrofurans based upon the IMSC methodology was developed by Overman et al. [53, 54, 94—96] For example, condensation of alcohol 221 with an aldehyde or a ketone in the presence of a Lewis acid leads to the formation of the carbocations 222a,b. The tertiary carboca-tion 222a undergoes a pinacol rearrangement and forms the desired heterocycle 224 (Scheme 13.82). Overman et al. used this approach during the synthesis of the various cladiellin diterpenes, which possess the core skeleton 224 [53]. 

Synthesis of Ethers by Alkoxymercuration-Demercuration 636 14-7 Industrial Synthesis Bimolecular Condensation of Alcohols 637 Summary Syntheses of Ethers (Review) 638 14-8 Cleavage of Ethers by HBr and HI 638... 

Bimolecular condensation of alcohols industrial synthesis (Sections 11-10B and 14-7)... 

Reduction of the 1,5-dithiocin 847 with LiAlH4 gave the l,5-dithiacyclooctan-7-ol 848 (30%). Condensation of alcohol 848 with methacryloyl chloride (CMAO) in presence of NEt3 afforded the 1,5-dithiocin 849 in low yield (Scheme 170) <1998W035955>. 

The ethers are compounds obtained by condensation of alcohols, with elimination of water. The most important ether is diethyl ether (ordinary ether), (C2H5) 20. It is made by treating ethanol with concentrated sulfuric acid, which serves as a dehydrating agent ... 

III. Condensation of Alcohols and Phenols with Sugars and Sugar Derivatives.. 163... 

The nature of support also plays a critical role in catalytic performance. Acidic supports such as A1203 favors the dehydration of ethanol to produce ethylene, which leads to carbon deposition on the catalyst surface.242,252,254,259 The carbon deposition can be minimized over basic supports such as Mg0.235, 241,258,259 However, these supports also favor condensation of alcohols to higher oxygenates.260 Interestingly,... 

Guerbet reaction. Condensation of alcohols at high temperature and pressure in the presence of sodium alkoxide or copper by a dehydrogenation, aldol condensation, and hydrogenation sequence. 

An ether can be considered as an alcohol derivative resulting from the condensation of alcohols. 

There is a clear economic incentive to develop heterogeneous catalysts to replace conventional homogeneous catalysts in many industrial processes. Efforts to formulate highly active and selective solid catalysts have been the subject of intense research. One such process of interest is the condensation of alcohols, aldehydes and ketones, known as aldol condensation, which is used industrially for the synthesis of a series of products used extensively in various industries (/). 

Acid-catalyzed condensation of alcohols (Sections 15.7 and 16.5) Two molecules of an alcohol condense in the presence of an acid catalyst to yield a dialkyl ether and water. The reaction is limited to the synthesis of symmetrical ethers from primary alcohols. 

Ostromislensky I.I (1916) Condensation of Alcohols and Aldehydes in Presence of Dehydrating Agents. Mechanism of the Process J. Russ. Phys. Chem. Soc. 48 1071. 

Condensation of alcohols and acidic components (NuH) on treatment with dialkyl azodicarboxylates and trialkyl- or triarylphosphines occurring primarily with inversion of configuration via the proposed intermediary oxyphosphonium salts ... 

Cumpstey I, Agrawal S, Martm-Matute B et al (2011) Iridium-catalysed condensation of alcohols and amines as a method for aminosugar synthesis. Chem Commiin 47(27) 7827—7829... 

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