Guerbet condensation

Performing this reaction in presence of metals like copper or nickel (Raney nickel)—especially in the case of lower molecular weight alcohols (C6-C10)— a dehydrative process occurs, the so-called Guerbet condensation reaction. Two alcohol molecules react to a 2-alkyl-branched isoalcohol ... 

Other references related to the Guerbet condensation are cited in the literature. ... 

Copper chromite magnesium oxide Modified Guerbet condensation s. U, 800... 

Higher molecular weight branched alcohols are produced by condensation of lower alcohols ia the Guerbet reaction. 

The Guerbet reaction can be used to obtain higher alcohols 2-propyl-1-heptanol [10042-59-8] from 1-pentanol condensation and 6-methyl-4-nonanol from 2-pentanol (80—83). Condensations with alkah phenolates as the base, instead of copper catalyst, produce lower amounts of carboxyhc acids and requke lower reaction temperatures (82,83). The crossed Guerbet reaction of 1-pentanol with methanol in the presence of sodium methoxide catalyst afforded 2-heptanol in selectivities of about 75% (84). 

The Guerbet reaction (386—389) involving condensation of ethanol in the presence of sodium ethoxide, catalyzed by potassium hydroxide and boric anhydride (390,391) or alkaline phosphates (392), gives / -butanol [71-36-3]. ... 

Other alcohols used in the surfactant industry, although of minor importance, are the Guerbet alcohols obtained by self-condensation of lower alcohols to yield products in the range of 16-26 carbons with a high degree of branching. 

In 1899 R. C. Guerbet discovered the self-condensation reaction of alcohols, which, via the aldehyde as an intermediate, lead to branched structures (2-alkyl alcohols) (Fig. 4.21) - the Guerbet alcohols. Starting with fatty alcohols from vegetable sources, such as octanol and decanol, the corresponding C1(, and C2o alcohols are produced (2-hexyldecanol and 2-octyldecanol, respectively). The reaction is carried out under alkali catalysis and high temperatures (>200 °C). Over the years, both products have proven to be efficient emollients, but are also used for other applications, such as plasticizers or components for lubricants (Fig. 4.21). 

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%). 

Highly branched and saturated oily Guerbet polymers having primary alcohols have been prepared by condensing 1,9-, 1,10-, or 1,12-aliphatic diols with behenyl alcohol and zinc oxide. To control the molecular weight, each polymer was capped with a C12 or higher fatty alcohol. 

Side reactions of the product aldehydes to form heavier products generally occur, particularly at higher-reaction temperatures, and usually account for s 9% of the product distribution. Aldol condensations, aldols, trimerizations, and Guerbet dimerizations of product alcohols are some of the more common ways to form heavy by-products. These side reactions are common to varying extents for all long-term... 

The Guerbet reaction is a complex combination of oxidation of a primary alcohol to an aldehyde, aldol condensation followed by dehydration, hydrogenation of the a,p-unsaturated aldehyde to a saturated alcohol, and oxidation of the aldehyde to an acid. The reaction is catalyzed by sodium and copper bronze and is carried out by heating the mixture in an autoclave at 270-300 °C and 50-60 atm for 6-10 h (equation 352). 

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. 

Branched long-chain alcohols (IV) obtained by condensation of lower alcohols (Guerbet synthesis) have some importance as lipophilic surfactants, emollients, and surfactant intermediates. Alcohols and sterols derived by saponification of wool wax, such as Amerchol 400 Amerchol), Argowax Westbrook Lanolin), Super Hartolan and Lanethyl Croda), sterols from vegetable waxes and oils, diols (such as 2,4,7,9-tetramethyl-decyne-5-diol-4,7 (V) that is known as wetting agent) as well as long-chain epoxy hydrolysates (1,2-diols) are also of some importance. 

The third of the reactions described above (i.e., the Guerbet reaction of primary alcohols) allows for the self-condensation/dimerization of alcohols to give the... 

Scheme 19 Preparation of p-all lated ketones via the dehydrogenation/aldol condensation/hydrogenation sequence (Guerbet reaction). ...

G. Guerbetalkohole R alcools guerbet The condensation of two moles of fatty alcohols (mostly Cs-Cn or Ci6-Cig) at 200-300 °C in the presence of an alkaline catalyst, e. g., KOH leads to branched alcohols (2-alkyl alcohols) ... 

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