11-Aminoundecanoic acid

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11-Aminoundecanoic acid
11-Aminoundecansäure Strukturformel.svg
3D model (JSmol)
ECHA InfoCard 100.017.652
Molar mass 201.31
Appearance white solid
Density 1,1720 g·cm−3
Melting point 188–191 °C
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

11-Aminoundecanoic acid is an organic compound with the formula H2N(CH2)10CO2H. This white solid is classified as an amine and a fatty acid. 11-Aminoundecanoic acid is a precursor to Nylon-11.[1]


As practiced by Arkema, 11-aminoundecanoic acid is prepared industrially from undecylenic acid, which is derived from castor oil.[2] The synthesis proceeds in four separate reactions:

1. Transesterification of castor oil to methyl ricinoleat:

Crude castor oil consists to about 90% of the triglyceride of ricinoleic acid. It is quantitatively transesterified with methanol to methyl ricinoleat (the methyl ester of ricinoleic acid) in the presence of the basic sodium methoxide at 80 °C within 1 h reaction time in a stirred reactor. At the end of the reaction, the resulting glycerol separates and the liquid methyl ester is washed with water to remove residual glycerol.


2. Pyrolysis of methylricinoleate to heptanal and methyl undecenoate:

Methylricinoleat is evaporated at 250 °C, mixed with hot steam (600 °C) in a 1:1 ratio and decomposed in a cracking furnace at 400 - 575 ° C at a retention time of about 10 seconds into its cleavage products heptanal and methyl undecenoate. The cleavage of the aliphatic chain occurs in this variant of the steam cracking selectively between the hydroxymethylene and the allyl-methylene group. Besides heptanal and methyl undecenoate, a mixture of methyl esters of saturated and unsaturated C18-carboxylic acids is obtained. This mixture is known under the trade name Esterol® and is used as a lubricant additive.

Pyrolyse von Ricinolsäuremethylester

3. Hydrolysis of methyl undecenoate to 10-undecenoic acid

The hydrolyis of the methyl ester with sodium hydroxide proceeds at 25 °C within 30 min with quantitative yield. After acidification with hydrochloric acid, solid 10-undecenoic acid (undecylenic acid) is obtained.

Hydrolyse Methylundecenoat.svg

4. Hydrobromination of 10-undecenoic acid to 11-bromoundecanoic acid

The undecenoic acid is dissolved in toluene and, in the presence of the radical initiator benzoyl peroxide (BPO), gaseous hydrogen bromide is added, in contrary to the Markovnikov rule ("anti-Markovnikov"). When cooled to 0 °C, the fast and highly exothermic reaction produces 11-bromoundecanoic acid in 95% yield - the Markownikov product 10-bromoundecanoic acid is produced in small quantities as a by-product. Toluene and unreacted hydrogen bromide are extracted under reduced pressure and resused.


5. Bromine exchange of 11-bromoundecanoic acid to 11-aminoundecanoic acid

11-Bromodecanoic acid is mixed at 30 °C with a large excess of 40% aqueous ammonia solution. When the reaction is complete, water is added and the mixture is heated to 100 °C to remove the excess ammonia.

Synthese von 11-Aminoundecansäure.svg

The acid can be recrystallized from water. For further purification, the hydrochloride of 11-aminoundecanoic acid, which is available by acidification with hydrochloric acid, can be recrystallized from a methanol/ethyl acetate mixture.[3]


11-aminoundecanoic acid is a white crystalline and odourless solid with low solubility in water.


  1. ^ Ben Herzog, Melvin I. Kohan, Steve A. Mestemacher, Rolando U. Pagilagan and Kate Redmond "Polyamides" in Ullmann's Encyclopedia of Industrial Chemistry 2013, Wiley-VCH, Weinheim. doi:10.1002/14356007.a21_179.pub3.
  2. ^ A. Chauvel, G. Lefebvre, Petrochemical Processes: Technical and Economic Characteristics, Band 2, S. 277, Editions Technip, Paris, 1989, ISBN 2-7108-0563-4.
  3. ^ M.-H. Koh et al.: Divergent process for C10, C11, and C12 α-amino acid and α,ω-dicarboxylic acid monomers of polyamides from castor oil as a renewable resource. In: Bull. Korean Chem. Soc., 33 (6), 1873–1878 (2012), doi:10.5012/bkcs.2012.33.6.1873.