Adipate esters

Plasticizers. About 2.5% of U.S. adipic acid consumed in 1988 was used in two basic types of adipic ester based plasticizers (195). Simple adipate esters prepared from Cg—alcohols are used especially as PVC plasticizers (qv). Eor special appHcations requiring low volatility or extraction resistance, polyester derivatives of diols or polyols are preferred. 

Raw Materials. PVC is inherently a hard and brittle material and very sensitive to heat it thus must be modified with a variety of plasticizers, stabilizers, and other processing aids to form heat-stable flexible or semiflexible products or with lesser amounts of these processing aids for the manufacture of rigid products (see Vinyl polymers, vinyl chloride polymers). Plasticizer levels used to produce the desired softness and flexibihty in a finished product vary between 25 parts per hundred (pph) parts of PVC for flooring products to about 80—100 pph for apparel products (245). Numerous plasticizers (qv) are commercially available for PVC, although dioctyl phthalate (DOP) is by far the most widely used in industrial appHcations due to its excellent properties and low cost. For example, phosphates provide improved flame resistance, adipate esters enhance low temperature flexibihty, polymeric plasticizers such as glycol adipates and azelates improve the migration resistance, and phthalate esters provide compatibiUty and flexibihty (245). 

Choice of the acid constituent can also be significant. For equivalent alcohol constituents, phthalate and adipate esters are approximately equivalent but both are considerably more efficient than the trimeUitate equivalent. 

Rubbers. Plasticizers have been used in mbber processing and formulations for many years (8), although phthaHc and adipic esters have found Htde use since cheaper alternatives, eg, heavy petroleum oils, coal tars, and other predominandy hydrocarbon products, are available for many types of mbber. Esters, eg, DOA, DOP, and DOS, can be used with latex mbber to produce large reductions in T. It has been noted (9) that the more polar elastomers such as nitrile mbber and chloroprene are insufficiendy compatible with hydrocarbons and requite a more specialized type of plasticizer, eg, a phthalate or adipate ester. Approximately 50% of nitrile mbber used in Western Europe is plasticized at 10—15 phr (a total of 5000—6000 t/yr), and 25% of chloroprene at ca 10 phr (ca 2000 t/yr) is plasticized. Usage in other elastomers is very low although may increase due to toxicological concerns over polynuclear aromatic compounds (9). 

SPE has been applied to phthalate esters (plasticisers in PVC), polar pesticides (agricultural usage) and for other continuous pollution monitoring problems and environmental analyses [272]. For these applications SPE has largely displaced LLE as the preferred technique for the preparation of liquid samples, e.g. EPA method 506 is concerned with the determination of phthalates and adipate esters in drinking water. 

The first stage of a reaction involved the addition of sodium dispersed in toluene to a solution of adipic ester in toluene. The subsequent addition of iodomethane (b.p. 42°C) was too fast and vigorous boiling ejected some of the flask contents. Exposure of sodium particles to air caused ignition, and a violent toluene-air explosion followed [ 1 ]. When a reagent as volatile and reactive as iodomethane is added to a hot reaction mixture, controlled addition, and one or more wide-bore reflux condensers are essential. A similar incident involving benzene was also reported [2]. 

For gas chromatographic analysis of the products, the submitter used a 3 ft. x 0.125 in. stainless steel column of 5% LAC-446 (cross-linked diethylene glycol-adipic ester) on Diatoport S (60-80 mesh), which was heated at 140° and swept with prepurified nitrogen at 30 ml. per minute. The four isomers were observed as three peaks at retention times of 3.08, 3.69, and 4.07 minutes. The checkers used aim. x 4 mm. glass column of 10% DECS on Gas Chrome Q (60-80 mesh), which was heated at 200° and swept with prepurified nitrogen at 75 ml. per minute. 

Balafas, D., Shaw, K.J. and Whitfield, F.B. (1999). Phthalate and adipate esters in Australian packaging materials. Food Chem., 65, 279-287. 

Determination of Phthalate and Adipate Esters in Drinking Water by LLE or LSE and GC with Photoionization... 

The most important adipate ester is also the di-2-ethylhexyl ester, DOA (Equation 15.4). 

By this approach, esters such as di(2-ethylhexyl) adipate and an oligomeric ester of neopentyl glycol have been synthesized recently by alcoholysis of dimethyl adipate ester and the corresponding alcohols, with alkaline earth metal compounds as the catalysts (171) (Scheme 30). These types of esters find application as lubricants, and it is suggested that they can be used as environment-friendly substitutes for petroleum-derived lubricants. The reactions were carried out with isooctane as a... 

Catalysis by metal ions has also been demonstrated in the hydrolysis of esters containing an a- or /I-carboxylate ion. The alkaline hydrolysis of potassium ethyl oxalate and potassium ethyl malonate is catalyzed by calcium, barium, hexaamino-cobalt(III), and thallous ion, in that order (22). The oxalate ester is catalyzed to a greater extent than the malonate ester, which in turn is more susceptible to catalysis by metal ion than the corresponding adipate ester. Alkali metal ions, on... 

Recently, polymer esters derived from azelaic esters and glycols were introduced by Unilever-Emery these show better compatibility and resistance to saponification compared with the polymer adipic esters. 

Cobalt is the catalyst of choice for the hydrocarboxylation of butadiene to adipic esters.89 The reaction is carried out in two steps, the first of which yields methyl-3-butenoate. This product can either be isolated or carried on to dimethyl adipate at high temperatures (Scheme 11). The first hydrocarboxylation occurs by the metal carboxylate insertion mechanism (vide supra). 

Wth adipate esters at the 21-hydroxyl group of methylprednisolone, no intramolecular catalysis is observed. Decreasing the chain length to succinate or malonate resulted in rate enhancements of 100- and 7700-fold, respectively, in the catalyzed region near pH 5. 

We have already seen (chapter 19) the synthesis of cyclopentanone itself 24 via the useful (3-ketoester 23 from adipate esters 22. In the same way unsaturated ketones 25 disconnect with an aldol in mind to the 1,6-dicarbonyl compound 26. There may again be regioselectivity questions in the cyclisation. 

Incidentally a yield of about 22% of adipic ester was obtained. 

TL 24 2009 (1983) (0-keto ester) 25 1241 (fi-diketones to /J-hydroxy ketones), 4623 (3-oxo glutarate and adipate esters), 5083 (a-sulfenyl-/J-keto esters) (1984) 26 101 (/J-keto esters), 771 (a-PhS ketone), 4213 (/J-keto esters) (1985) 27 565 (/J-diketones to /J-hydroxy ketones), 1915 (a-keto esters) 2091 (/J-keto esters), 2657 (/J-keto esters), 3547 (2-acyl- 1,3-dithianes 2-acylthiazoles), 4737 (a-chloro ketones), 4817 (a-PhSOj ketone), 5275 (/J-keto esters and amides), 5281 (/ -keto esters), 5397 (a-chloro ketone, /J-keto ester), 5405 (/J-keto thio- and dithioesters) (1986) 28 2709 (/ -chloro-a-keto ester), 3189 (/J-keto ester) (1987) 29 4769 (3- and 4-nitro ketones), 4865 (/J-keto ester), 6167 (5-acetyl-2-isoxazolines) (1988) 30 2707 (yS-keto ester), 3701, 5705 (/J-keto ester) (1989) 31 1159 (/J-keto ester), 1615 (/J-keto ester), 1811, 3631 (/J-keto esters), 4025 (a-hydroxy ketone), 4195 (2-acyl-2-alkenoate ester), 5575 (y- and 5-keto sulfones), 7463 (/J-diketone to /f-hydroxy ketone)... 

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