Fatty alcohols

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Structure of the fatty alcohol 1-octanol
Fatty alcohols with a linear, saturated alkyl radical are represented in a simplified manner using this formula. With octanol, n = 6.

Fatty alcohols are aliphatic , long-chain, monohydric, mostly primary alcohols . The hydrocarbon residues in native fatty alcohols are often unbranched, synthetic fatty alcohols are often also branched. The carbon chain has 6 to 22 carbon atoms and can also be mono- or polyunsaturated .

Fatty alcohols are found in natural waxes , bound as carboxylic acid esters , e.g. B. in wool wax or whale rat and are often called wax alcohols . Such alcohols usually contain an even number of carbon atoms, which can also be 36 or more carbon atoms.

Fatty alcohols are used in the chemical industry , e.g. B. produced by reducing fatty acids or petrochemically . Fatty alcohols are used directly as a nonionic surfactant and in the manufacture of various other surfactants .

structure

The table shows examples of fatty alcohols; Sometimes the higher molecular weight representatives from around 24 carbon atoms are counted among the wax alcohols. The nomenclature corresponds to the nomenclature of the alkanes , supplemented by the ending -ol for the additional alcohol group. Their common names are often used (see in brackets).

C atoms: double bonds Surname Gross formula
saturated fatty alcohols
6-0 1-hexanol C 6 H 13 OH
7-0 1-heptanol C 7 H 15 OH
8-0 1-octanol C 8 H 17 OH
10-0 1-decanol C 10 H 21 OH
12: 0 1-dodecanol (lauryl alcohol) C 12 H 25 OH
14: 0 1-tetradecanol (myristyl alcohol) C 14 H 29 OH
16: 0 1-hexadecanol (cetyl alcohol) C 16 H 33 OH
17: 0 1-heptadecanol (margaryl alcohol) C 17 H 35 OH
18: 0 1-octadecanol (stearyl alcohol) C 18 H 37 OH
20: 0 1-eicosanol (arachidyl alcohol) C 20 H 41 OH
22: 0 1-docosanol (behenyl alcohol) C 22 H 45 OH
24: 0 1-tetracosanol (lignoceryl alcohol) C 24 H 49 OH
26: 0 1-hexacosanol (ceryl alcohol) C 26 H 53 OH
28: 0 1-octacosanol (montanyl alcohol) C 28 H 57 OH
30: 0 1-triacontanol (melissyl alcohol) C 30 H 61 OH
monounsaturated fatty alcohols
16: 1 cis -9-hexadecen-1-ol (palmitoleyl alcohol) C 16 H 31 OH
18: 1 cis -9-octadecen-1-ol (oleyl alcohol) C 18 H 35 OH
18: 1 trans -9-octadecen-1-ol (elaidyl alcohol) C 18 H 35 OH
18: 1 cis -11-octadecen-1-ol C 18 H 35 OH
polyunsaturated fatty alcohols
18: 2 cis , cis -9,12-octadecadien-1-ol ( linoleyl alcohol ) C 18 H 33 OH
18: 3 6,9,12-octadecatrien-1-ol (γ-linolenyl alcohol) C 18 H 31 OH

Manufacturing

Reduction of fatty acid esters

Fatty alcohols can be produced by the reduction and hydrolysis of waxes such as whale rat with elemental sodium ( Bouveault-Blanc reaction ). The first technical presentation was carried out in 1928 by the hydrogenation works in Rodleben . This process is no longer of technical importance for the production of fatty alcohols.

Hydrogenation of fatty acids and fatty acid esters

As a rule, fatty alcohols are made from renewable raw materials , for example by hydrogenating fatty acids from vegetable oils (see also oleochemistry ). The carboxy group  (-COOH) typical of carboxylic acids is converted into the hydroxyl group (-OH) typical of alcohols. The carbon atom of the COOH group is retained as -CH 2 -OH. So z. B. Cetyl alcohol  (C 16 ) as a product of palmitic acid from palm oil or coconut oil and stearyl alcohol (C 18 ) obtained from stearic acid.

Hydroformylation of olefins

Fatty alcohols can be produced from olefins and carbon monoxide by hydroformylation (oxo synthesis) on cobalt and rhodium catalysts. The aldehydes formed are converted into alcohols by hydrogenation. The alcohols obtained in this way are also called oxo alcohols and, thanks to this synthetic route, can also be branched and odd-numbered.

Ziegler-Alfol synthesis

Reactivity of triethylaluminum :
[1a] build-up reaction, [1b] displacement, [2a] oxidation, [2b] hydrolysis

Fatty alcohols with even carbon chains can be produced by reacting ethene with triethylaluminum. In the first step, hydrogen and triethylaluminum are produced as an intermediate product, diethylaluminum hydride , from metallic aluminum , which further reacts with ethene to form triethylaluminum. About two thirds of the triethylaluminum formed is fed back into the initial reaction (1), one third is used for the build-up reaction.

The distribution of the chain length corresponds to a Poisson distribution , which is optimized for the range from 10 to 16 carbons by suitable choice of the process parameters. During the oxidation of the complex with oxygen and subsequent hydrolysis with sulfuric acid and water, nature-identical Ziegler alcohols , also called alfoles, are formed, which are used as fatty alcohol sulfates or, after ethoxylation and sulfation, as alkyl ether sulfates in personal care products and detergents and cleaning agents.

Synol procedure

In synol processes, fatty alcohols are obtained from carbon monoxide and hydrogen under similar conditions as in the Fischer-Tropsch synthesis .

Bashkirov procedure

During the oxidation of paraffins in the presence of boric acid by the Bashkirov process, mainly secondary alcohols are produced .

Guerbet condensation

By Guerbet condensation of linear, primary alcohols at temperatures of about 180 to 300 ° C in the presence of, for example, potassium hydroxide branched in the alpha position fatty alcohols leads to the formation of primary,.

biosynthesis

Many organisms use fatty alcohols for various purposes, the most famous of which is the production of beeswax by the honeybee . Activated fatty acid esters from fatty acids and coenzyme A are enzymatically reduced to fatty alcohol by an acyl-CoA reductase in two steps. In the first step, the ester is reduced to the aldehyde and this to the fatty alcohol. As a cofactor is NADPH needed.

use

Fatty alcohols such as stearyl alcohol and cetyl alcohol are used as nonionic surfactants and can be used as the basis for many creams and ointments . They are not miscible with water, but can be converted into fatty alcohol sulfates by reaction with gaseous sulfur trioxide and subsequent neutralization with bases such as sodium hydroxide solution . These are of great importance as anionic surfactants in detergents and personal care products. By ethoxylation can be fatty alcohol ethoxylates win as nonionic surfactants that are used in personal care products.

literature

  • Keyword Fatty Alcohols In: Hans Zoebelein (Ed.): Dictionary of Renewable Resources. 2nd edition, Wiley-VCH, Weinheim and New York 1996; Pp. 101-102. ISBN 3-527-30114-3 .

Web links

Individual evidence

  1. ↑ Spectrum online lexica: Entry on fatty alcohols . In: Lexikon der Chemie, accessed on December 15, 2015.
  2. ↑ Entry on fatty alcohols. In: Römpp Online . Georg Thieme Verlag, accessed on January 10, 2013.
  3. ↑ Der Brockhaus, Natural Science and Technology, Spectrum Akademischer Verlag GmbH, Heidelberg, 2003.
  4. ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 6: T-Z. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1988, ISBN 3-440-04516-1 , pp. 4562-4563.
  5. ↑ a b Dr. Z Presents: All about fatty alcohols ( Memento from September 27, 2007 in the Internet Archive ), 43-page pdf with comprehensive information on fatty alcohols, in English, accessed on March 22, 2010
  6. ↑ S. Würkert: Hydrogenation of fatty acid methyl esters to saturated fatty alcohols , as a 205-page pdf, accessed on March 22, 2010.
  7. ^ Christoph Elschenbroich, Albrecht Salzer , Organometallchemie , 3rd edition, Teubner, Stuttgart, 1990.
  8. ^ Wilhelm Keim, Arno Behr and Günter Schmitt: Fundamentals of industrial chemistry. Technical products and processes , ISBN 3-7935-5490-2 (Salle), ISBN 3-7941-2553-3 (Sauerländer), pp. 188–189.
  9. ↑ W. Hagge: Modern developments and economic importance of detergents. In: fats, soaps, paints. 67, 1965, pp. 205-211, doi : 10.1002 / lipi.19650670312 .
  10. ↑ Gunther Czichocki, Helga Brämer, Inge Ohme: Production, properties and analysis of ether sulfates. In: Journal of Chemistry. 20, 1980, pp. 90-94, doi : 10.1002 / zfch.19800200303 .
  11. ↑ William Wenzel: The Synolverfahren. A New Synthesis of Aliphatic Alcohols. In: Angewandte Chemie. 20, 1948, p. 225, doi : 10.1002 / ange.19480200902 .
  12. ↑ Noweck, Klaus, and Wolfgang Grafahrend. "Fatty alcohols." Ullmann's encyclopedia of industrial chemistry (2006).
  13. ↑ Ramesh Varadaraj, Jan Bock, Paul Valint, Stephen Zushma, Robert Thomas: Fundamental interfacial properties of alkyl-branched sulfate and ethoxy sulfate surfactants derived from Guerbet alcohols. 1. Surface and instantaneous interfacial tensions. In: The Journal of Physical Chemistry. 95, 1991, p. 1671, doi : 10.1021 / j100157a033 .
  14. ↑ Janine Hellenbrand Characterization of Acyl-CoA-Reductases Dissertation RWTH Aachen 2012