Guerbet reaction

The Guerbet reaction, named after Marcel Guerbet (1861-1938), is an organic reaction converting a primary aliphatic alcohol into its β-alkylated dimer alcohol with loss of one equivalent of water. [ cite journal
title = Condensation de l'alcool isopropylique avec son dérivé sodé; formation du méthylisobutylcarbinol et du diméthyl-2.4-heptanol-6
author = Marcel Guerbet
journal = Comptes rendus de l'Académie des sciences
volume = 149
issue =
pages = 129-132
year = 1909
url = http://gallica.bnf.fr/ark:/12148/bpt6k3103r/f129.table
doi = ] This reaction requires a catalyst and elevated temperatures.

The original 1899 publication concerned the conversion of "n"-butanol to "2-ethyl-1-hexanol". The alcohols dervied from this reaction are called Guerbet alcohols. Application of long-chained aliphatic alcohols gives access to surfactants.

The reaction requires alkali metal hydroxides or alkoxides and hydrogenation catalysts such as Raney Nickel at higher temperature (220 °C) and pressure.

Reaction mechanism

The reaction mechanism for this reaction is a four-step sequence. In the first step the alcohol is oxidized to the aldehyde. These intermediates then react in an Aldol condensation to the vinyl aldehyde which the hydrogenation catalyst then reduces to the alcohol. [cite journal
title = On the mechanism of the Guerbet reaction
author = S. Veibel and J. I. Nielsen
journal = Tetrahedron
volume = 23
issue = 4
pages = 1723-1733
year = 1967
url =
doi = 10.1016/S0040-4020(01)82571-0 ]

The Cannizzaro reaction is a competing reaction when two aldehyde molecules react by disproportionation to form the corresponding alcohol and carboxylic acid. Another side reaction is the Tishchenko reaction.

cope

New catalyst systems are actively researched which can bring down the processing temperature. In one study 1-pentanol is reacted with an iridium dehydrogenation catalyst (Cp* stands for the pentamethylcyclopentadiene ligand) and potassium tert-butoxide as a base in "p"-xylene [cite journal
title = Guerbet Reaction of Primary Alcohols Leading to -Alkylated Dimer Alcohols Catalyzed by Iridium Complexes
author = Toyomi Matsu-ura, Satoshi Sakaguchi, Yasushi Obora, and Yasutaka Ishii
journal = Journal of Organic Chemistry
volume = 71
issue = 21
pages = 8306 - 8308
year = 2006
url =
doi = 10.1021/jo061400t ] . A small amount of the diene "1,7-octadiene" is required as a proton acceptor.

ee also

* Two related reactions in the production of butadiene are the Lebedev process and the Ostromisslenskii reaction.

External links

* "A Review of Guerbet Chemistry" Anthony J. O’Lenick, Jr. http://www.zenitech.com [http://www.zenitech.com/documents/guerbet_chemistry.pdf#search=%22Guerbet%20Reaction%22 Link]

References