Sebacic Acid Route

The diacid (BB) monomer used for the AABB polyamide PA610 and PAlOlO is sebacic acid (1,8-octanedicarboxylic acid). While the process to arrive at this monomer is straightforward, it too will receive a collective term, the sebacic acid route. 

The diamine (AA) monomer used for the PA610 AABB polyamide is hexamethylene diamine (HMDA), which is produced petrochemically from butadiene. 

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Alkali fusion of oleic acid at about 350°C ia the Varrentrapp reaction causes double-bond isomerization to a conjugated system with the carboxylate group followed by oxidative cleavage to form palmitic acid (75). In contrast, alkaU fusion of riciaoleic acid is the commercial route to sebacic acid [111 -20-6] ... 

Seb cic Acid. Sebacic acid [111-20-6] C QH gO, is an important intermediate in the manufacture of polyamide resins (see Polyamides). It has an estimated demand worldwide of approximately 20,000 t/yr. The alkaline hydrolysis of castor oil (qv), which historically has shown some wide fluctuations in price, is the conventional method of preparation. Because of these price fluctuations, there have been years of considerable interest in an electrochemical route to sebacic acid based on adipic acid [124-04-9] (qv) as the starting material. The electrochemical step involves the Kolbn-type or Brown-Walker reaction where anodic coupling of the monomethyl ester of adipic acid forms dimethyl sebacate [106-79-6]. The three steps in the reaction sequence from adipic acid to sebacic acid are as follows ... 

An example of the first route is given in the preparation of nylon 66, which is made by reaction of hexamethylenediamine with adipie acid. The first 6 indicates the number of carbon atoms in the diamine and the second the number of carbon atoms in the acid. Thus, as a further example, nylon 6.10 is made by reacting hexamethylenediamine with sebacic acid (HOOC (CH2)s"COOH). (In this context the numbers 10,11 and 12 are considered as single numbers the need to use two digits results simply from the limitations of the decimal system.)... 

In Japan the need for new technology was answered by the development of an electrolytic route to sebacic acid(33). The Kolbe type electrolytic process developed by Asahi involves dimerization of adipic acid half methyl ester salt to give dimethyl sebacate(34). The dimerization proceeds in 92% yield with 90% selectivity based on the adipate half ester. The main drawbacks of this process are the cost of energy utilized by the electrolytic process and the cost of adipic acid. A Chem Systems report indicates a small advantage for the Asahi electrolytic process with ample room for new technology development(35). 

Methyl 2, -pentadienoate self-dimerization as a potential route to sebacic acid precursors was extensively evaluated. Homogeneous metal catalyzed dimerization of compounds containing conjugated double bonds is known to give cyclic, branched, and linear dimers(43-45). At higher temperatures or in the presence of many zero-valent metal catalysts, cyclodimerization (Equation 12.) is the only observable reaction. 

A commercially attractive palladium catalyzed oxidative carbonylation route to adipic and sebacic acid has been developed which uses butadiene and the elements of synthesis gas as the raw... 

Ester chlorides of dicarboxylic acids can be converted into ester amides without attack on the ester group. E.g., the methyl ester chloride from sebacic acid gives, with aqueous ammonia, a 95% yield of the ester amide.592 Treatment of chloroformic esters with ammonia576,593 or a primary594 or secondary amine595 is a much used route to urethanes. 

This process results in low yields of sebacic acid (about 50% based on the castor oil) but, nevertheless, other routes have not proved competitive. Sebacic acid is a colourless crystalline solid, m.p. 134.5°C. 

Aside from whether they are directly active per se, or merely as precursors of active metabolic intermediates, carcinogenic polycyclic hydrocarbons can initiate carcinomas (e.g. epithelioma) at the point of application on the skin (the commonest mode of study), or can lead to distant tumours, as in bronchogenic cancer [23]. The mechanism probably includes solubilisation of the carcinogens (by proteins, nucleoproteins, fatty acid esters, etc. or even in aqueous solution [58]), so as to enable them to traverse the dermis (possibly via an external solvent) and thus react in the epidermis, which possesses a lipoid barrier. Alternatively, appendageal transport routes (hair follicles, sweat glands, sebaceous glands) may be used [59]. When carcinogens act at a distance, as with liver, breast, bladder and other internal cancers, an internal transport mechanism or medium is evidently needed. 

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