11-Aminoundecanoic acid

The starting point for this amino acid, from which nylon 11 is obtained, is the vegetable product castor oil, composed largely of the triglyceride of ricinoleic acid. This is first subjected to treatment with methanol or ethanol to form the appropriate ricinoleic acid ester. 

This amino acid may also be produced via telomerisation reactions (see below). 

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Nylon-11. Nylon-11 [25035-04-5] made by the polycondensation of 11-aminoundecanoic acid [2432-99-7] was first prepared by Carothers in 1935 but was first produced commercially in 1955 in France under the trade name Kilsan (167) Kilsan is a registered trademark of Elf Atochem Company. The polymer is prepared in a continuous process using phosphoric or hypophosphoric acid as a catalyst under inert atmosphere at ambient pressure. The total extractable content is low (0.5%) compared to nylon-6 (168). The polymer is hydrophobic, with a low melt point (T = 190° C), and has excellent electrical insulating properties. The effect of formic acid on the swelling behavior of nylon-11 has been studied (169), and such a treatment is claimed to produce a hard elastic fiber (170). 

Nylon-11. This nylon is produced from 11-aminoundecanoic acid, which is derived from castor oil. The acid is polymerized by heating to 200°C with continuous removal of water. Catalysts such as phosphoric acid are frequentiy used. There is no appreciable amount of unreacted monomer left in the product. 

Undecenoic acid is the starting point for making 11-aminoundecanoic acid [2432-99-7] and nylon-11 (see Castor oil Polyamides). 

Cracking of the ester at about 500°C leads to the formation of the undecylenic acid ester together with such products as heptyl alcohol, heptanoic acid and heptaldehyde. Undecylenic acid may then be obtained by hydrolysis of the ester. Treatment of the acid by HBr in the presence of a peroxide leads to w-bromoundecanoic acid together with the 10-isomer, which is removed. Treatment of the w-bromo derivative with ammonia leads to w-aminoundecanoic acid, which has a melting point of 50°C (Figure 18.8). 

This polymer may be prepared by stirring the molten w-aminoundecanoic acid at about 220°C. The reaction may be followed by measurements of the electrical conductivity of the melt and the intrinsic viscosity of solutions in w-cresol. During condensation 0.4-0.6% of a 12-membered ring lactam may be formed by intramolecular condensation but this is not normally removed since its presence has little effect on the properties of the polymer. 

Polyamide is available commercially as polyamide-6 (based on e-aminocapro-lactam, Macherey-Nagel) and as polyamide-11 (based on 11-aminoundecanoic acid, Merck). The lipophilic properties of these are different, thus altering their chromatographic selectivity. 

To a 50-mL three-necked flask (Fig. 3.18b) equipped with a stirrer (comprised of a stainless steel shaft and paddle), a head for the distillation of water, and a nitrogen inlet is added 20 g of purified 11-aminoundecanoic acid. The flask is then purged with nitrogen for 5 min. The flask is warmed in a silicon oil bath to 220° C and maintained at this temperature for 10 h. After raising the stirrer from the molten mass, the reaction is cooled under nitrogen and the resultant polymer removed by breaking the glass. The Tm of the polymer is 185—190° C and the rjmh in m-cresol (0.5% at 35°C) is 0.6—0.7. 

It is expected that, if instead of laurolactam, 11-aminoundecanoic acid is used, then die reaction can be carried out at atmospheric pressure, as in Example 10. 

The important but unusual fatty acid ricinoleic acid, or 12-hydroxyoleic acid, is a major component of castor oil (>87%) and is also found in useful quantities in ergot. The metal salts of the acid find use in dry-cleaning soaps but the majority is converted to aminoundecanoic acid (Scheme 6.6) which is used to make nylon 11. Nylon 11 has very good chemical and shock-resistance properties, which have led to it being used in the automotive industry. Ricinoleic triglyceride is initially transesterified to the methyl ester. This is heated to 300 °C at which temperature it is... 

Scheme 6.6 Conversion of ricinoleic acid into aminoundecanoic acid...

The process of self condensation of co-amino acids involves reactions of the type shown in Fig. 23.6 b). This type of reaction is used to make polymers, such as nylon 11, from molten 11-aminoundecanoic acid, which is stirred at 220 °C. Such specialty nylons are made in much smaller quantities than nylon 6 and are thus more likely to be made in a batch reactor than in a continuous reaction tube. 

Principal raw materials are adipic acid, sebacic acid, hexalmethylene diamine, caprolactam. 10-aminoundecanoic acid and dodecyl lactam. 

Steinbrunn and Wenz recently reported poly(amide-CD rotaxane)s 53 via a very imaginative approach [90,91]. First, the CD was threaded on to an a,co-amino acid in water to give a pseudorotaxane monomer. An NMR study showed that two CD molecules were threaded per linear molecule for 11-aminoundecanoic acid. The X-ray powder pattern indicated that these rotaxanes stacked like channels in the solid state this provided the basis for solid state polymerization at 200°C to afford polyamide 53 with m/n=2 ... 

Other lipophilic derivatives of EDTA and DTPA were synthesized by condensing the bisanhydride of the former with phosphatidylethanolamine to give PE-EDTA (16)121 whereas that of the latter was condensed with 11-aminoundecanoic acid to give Puchel, 17,122. PE-EDTA failed to mobilize plutonium from the hamster, although studies with PE-[14C]EDTA established the uptake of the radiolabel into the liver. 

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