2.5- Dimethyl adipic acid

In 196146 the initial work on ( —)-(/t)-dimenthyl fumarate (l)47 was revised and a diastereomeric ratio of 78.5 21.5 (15,25) for the aluminum chloride promoted addition to 1,3-butadiene (2) was reported. The absolute configuration was established by degradation of the major cycloadduct 3 to threo-2>,4-dimethyl adipic acid (5). Absence of Lewis acids reverses the sense of chiral induction [d.r. 51.2 48.8 (l/ ,27 )]. These observations are rationalized by means of a modified Prelog model. 

Amidation. Heating of the diammonium salt or reaction of the dimethyl ester with concentrated ammonium hydroxide gives adipamide [628-94-4] mp 228°C, which is relatively insoluble in cold water. Substituted amides are readily formed when amines are used. The most industrially significant reaction of adipic acid is its reaction with diamines, specifically 1,6-hexanediamine. A water-soluble polymeric salt is formed initially upon mixing solutions of the two materials then hea ting with removal of water produces the polyamide, nylon-6,6. This reaction has been studied extensively, and the hterature contains hundreds of references to it and to polyamide product properties (31). 

Reduction. Hydrogenation of dimethyl adipate over Raney-promoted copper chromite at 200°C and 10 MPa produces 1,6-hexanediol [629-11-8], an important chemical intermediate (32). Promoted cobalt catalysts (33) and nickel catalysts (34) are examples of other patented processes for this reaction. An eadier process, which is no longer in use, for the manufacture of the 1,6-hexanediamine from adipic acid involved hydrogenation of the acid (as its ester) to the diol, followed by ammonolysis to the diamine (35). 

CO, and methanol react in the first step in the presence of cobalt carbonyl catalyst and pyridine [110-86-1] to produce methyl pentenoates. A similar second step, but at lower pressure and higher temperature with rhodium catalyst, produces dimethyl adipate [627-93-0]. This is then hydrolyzed to give adipic acid and methanol (135), which is recovered for recycle. Many variations to this basic process exist. Examples are ARCO s palladium/copper-catalyzed oxycarbonylation process (136—138), and Monsanto s palladium and quinone [106-51-4] process, which uses oxygen to reoxidize the by-product... 

The first CO route to make adipic acid is a BASF process employing CO and methanol in a two-step process producing dimethyl adipate [627-93-0] which is then hydroly2ed to the acid (43—46). Cobalt carbonyl catalysts such as Co2(CO)g are used. Palladium catalysts can be used to effect the same reactions at lower pressures (47—49). 

An electrooxidation process was developed by Asahi Chemical Industry ia Japan, and was also piloted by BASF ia Germany. It produces high purity sebacic acid from readily available adipic acid. The process consists of 3 steps. Adipic acid is partially esterified to the monomethyl adipate. Electrolysis of the potassium salt of monomethyl adipate ia a mixture of methanol and water gives dimethyl sebacate. The last step is the hydrolysis of dimethyl sebacate to sebacic acid. Overall yields are reported to be about 85% (65). 

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 ... 

Figure 12.12 THM GC/MS curves of a Winsor Newton lemon alkyd paint (a) and of an alkyd sample taken from Fontana s work Concetto spaziale (1961) (b). Peak assignments 1, 1,3 dimethoxy 2 propanol 2, 1,2,3 trimethoxy propane 3, 3 methoxy 1,2 propandiol 4, 4 chloro benzenamine 5, 3 methoxy 2,2 bis(methoxymethyl) 1 propanol 6, 3 chloro N methyl benzenamine 7, 3 methoxy 2 methoxymethyl 1 propanol 8, 4 chloro N methyl benzenamine 9, phthalic anhydride 10, 3 chloro 4 methoxy benzenamine 11, suberic acid dimethyl ester 12, dimethyl phthalate 13, azelaic acid dimethyl ester 14, sebacic acid dimethyl ester 15, palmitic acid methyl ester 16, oleic acid methyl ester 17, stearic acid methyl ester 18, 12 hydroxy stearic acid methyl ester 19, 12 methoxy stearic acid methyl ester 20, styrene 21, 2 (2 methoxyethoxy) ethanol 22, 1,1 oxybis(2 methoxy ethane) 23, benzoic acid methyl ester 24, adipic acid dimethyl ester 25, hexadecenoic acid methyl ester 26, dihydroisopimaric acid methyl ester 27, dehydroabietic acid methyl ester 28, 4 epidehydroabietol...

Dimethylquinoline, 21 189 Dimethyl sebacate, from adipic acid,... 

The dimethyl ester of adipic acid, rather than adipic acid, was used as a transesterification substrate. Reaction rate studies had shown that the transesterification would be much faster than the esterification reaction. It was considered that the rate of attack on the oxazolidine ring by methanol would be slower than the rate of attack by water and that the ring opening would not be catalysed by the enzyme, whereas the rate of the transesterification would be increased significantly, particularly at the low temperature of the enzymatic esterification. 

A solution of borane in tetrahydrofuran reduces esters at room temperature only slowly [977]. Under such conditions free carboxylic groups of acids are reduced preferentially monoethyl ester of adipic acid treated with 1 mol of borane in tetrahydrofuran at — 18° to 25° gave 88% yield of ethyl 6-hydroxy-hexanoate [977]. Borane-dimethyl sulfide in tetrahydrofuran was used for... 

One process that capitalizes on butadiene, synthesis gas, and methanol as raw materials is BASF s two-step hydrocarbonylation route to adipic acid(3-7). The butadiene in the C4 cut from an olefin plant steam cracker is transformed by a two-stage carbonylation with carbon monoxide and methanol into adipic acid dimethyl ester. Hydrolysis converts the diester into adipic acid. BASF is now engineering a 130 million pound per year commercial plant based on this technology(8,9). Technology drawbacks include a requirement for severe pressure (>4500 psig) in the first cobalt catalyzed carbonylation step and dimethyl adipate separation from branched diester isomers formed in the second carbonylation step. 

Adipic Acid Precursor Other Carbonylation Products Carbon Dioxide Dimethyl Oxalate... 

Carbon monoxide insertion into the carbon-palladium bond of 4, followed by nucleophilic displacement with methoxide, gives a 4 1 mixture of trans and cis-dimethyl hex- endioate which is the desired l, 4-dicarbonylaton precursor to adipic acid. 

Palladium catalyst stability, recovery and recycle are the key to viable commercial technology. Continuous palladium recovery and recycle at 99.9% efficiency is critical to the economics of the process. Traditional catalyst recovery methods fail since the adipic acid precursor, dimethyl hex- -enedioate, is high boiling and the palladium catalytic species are thermally unstable above 125 C. Because of this problem, a non-traditional solvent extraction approach to catalyst recovery has been worked out and implemented at the pilot plant scale. Since patents have not issued, process detail on catalyst separation, secondary palladium recovery, and product recovery cannot be included in this review. 

Following hydrogenation over palladium on carbon(33), dimethyl adipate hydrolysis to adipic acid is carried out using a strong mineral acid such as sulfuric acid. Hydrolysis is nearly quantitative with a selectivity of 99.5%. Since the adipic acid from the oxycarbonylation process contains no branched by-product acids, as is the case with the commercial oxidation process, extensive recrystallization is not required to produce a polymer grade material. Results indicate that the dried adipic acid crystals contain less than. 5 weight % moisture and are 99.95 weight % pure on a dry basis. 

Direct use of dimethyl adipate from the oxycarbonylation process to produce nylon 6,6 could be an attractive alternative to current adipic acid/nylon 6,6 technology. Dimethyl adipate condensation with hexamethylene diamine would give methanol rather than water. Reactors, which currently use caprolactam to prepare nylon 6, could also easily be retrofitted to produce nylon 6,6. Dimethyl hex- nedioate or dimethyl adipate are also useful raw materials for preparation of other high volume chemicals including hexamethylene diamine, caprolactam, and 1, -hexanediol. 

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). 

This structure was conclusively established by carboxylation of the dimer which produced a mixture of stereoisomers of 2-5-dimethyl-2,5-diphenyl-adipic acids (19). 

Glularic Acid. Until 1990-1991 glularic acid was available commercially from DuPont as a by-product in the production of adipic acid. It is no longer available, but DuPont produces dimethyl glutaratc and mixtures of dimethyl succinate and dimethyl glutarate. as well as mixtures of dimethyl glutarate and dimethyl adipate. 

In a 500-ml single-necked flask containing a magnetic stirrer bar, place 58.5 g (0.4 mol) of adipic acid, 16 g (20 ml, 0.5 mol) of methanol, 83.2 g (0.8 mol) of 2,2-dimethoxypropane and 0.5 g of toluene-p-sulphonic acid. Fit a reflux condenser to the flask and stir the mixture magnetically for 4 hours in a water bath kept at 45 °C. Rearrange the condenser for distillation and distil off acetone (b.p. 56 °C) and methanol (b.p. 64 °C) on the water bath. Distil the residue under reduced pressure (water pump) and collect the dimethyl adipate, b.p. 130°C/25mmHg. The yield is 54.9 g (79%). 

Copper or silver can be used to condense /3-iodo-propionic acid to adipic acid, and also for condensing a-brom-propionic ester to dimethyl succinic ester... 

The necessity for the continuous removal of water can be avoided by operating in a system composed of an aqueous and a non-aqueous layer. When a mixture of adipic acid, methanol, sulfuric acid, and ethylene chloride is heated, dimethyl adipate passes into the ethylene chloride layer the lower layer contains the water (19). 

Butanediol, adipic acid, butyrate, diethyl succinate, dimethyl succinate, maleic anhydride, polyamides, polybutylene succinate, pyrrolidinones, succindiamide, tetrahydrofuran... 

The world-wide production of PA (excluding fibers) in 1997 was 1.6x10 t, with a 75 % use of casting processed materials. For food contact articles the following can be used as starting materials straight chain u -amino acids (C6-C12) and their lactams adipic acids, azelaic acids, sebacic acids, dodecane dicarboxylic acids and heptadecane-dicarboxylic acids salts with hexamethylenediamine isophthalic acid, bis(4-aminocy-clohexyl)-methane, 2,2-bis(4 -aminocyclohexyl)-propane, 3,3 -dimethyl-4,4 -diamino-dicyclohexyl-methane, terephthalic acid or its methylester, l,6-diamino-2,2,4-tri-methylhexane, 1,6-diamino-2,4,4-trimethylhexane, l-amino-3-amino-methyl-3,5,5-tri-methylhexane. 

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