Diacids

Nylon A class of synthetic fibres and plastics, polyamides. Manufactured by condensation polymerization of ct, oj-aminomonocarboxylic acids or of aliphatic diamines with aliphatic dicarboxylic acids. Also rormed specifically, e.g. from caprolactam. The different Nylons are identified by reference to the carbon numbers of the diacid and diamine (e.g. Nylon 66 is from hexamethylene diamine and adipic acid). Thermoplastic materials with high m.p., insolubility, toughness, impact resistance, low friction. Used in monofilaments, textiles, cables, insulation and in packing materials. U.S. production 1983 11 megatonnes. 

Organic polyesters, obtained either from a diacid and a mono-alcohoi, or from poly-alcohols and a monoacid, or from di-alcohols and a diacid. This class represented 29% of the synthetic base market in France in 1992. 

The organophilic part R can come from a natural fatty acid whose carbon number is around 18 and whose chain contains a number of unsaturated bonds. Dimers of fatty acids (Cgg diacids) have also been used. 

If two equivalents of the reagents are used, disubstitution to ECeC-CH(E)R occurs in most cases, but interestingly the reaction of LiCeCCH(Li)R with an excess of COj gives mainly the allenic dicarboxylic acids. These are probably the result of a rapid isomerization of the primary dilithium salt of the acetylenic diacid during the work-up or during the reaction of the dilithio compound with COj ... 

We presume that the dilithiopropyne causes partial isomerization into the allenic derivative. The treatment with KOH is to complete this transformation. When the latter treatment was not carried out, considerable amounts of the acetylenic diacids were sometimes found in the crude product. 

The low yield of the diacid may be explained by incomplete carboxylation, due to the slight solubility of the dilithio compound. 

The 2,4- or 2,5-diacids and 2,4,5-triacids have been prepared in good yields (40 to 50%) by hydrolysis of the esters obtained by heterocyclization (7, 12). 

Excluding enantiomers there are three isomeric cyclopropanedicarboxyhc acids Two of them A and B are constitutional isomers of each other and each forms a cyclic anhydnde on being heated The third diacid C does not form a cyclic anhydride C is a constitutional isomer of A and a stereoisomer of B Identify A B and C Construct molecular models of the cyclic anhy dndes formed on heating A and B Why doesn t C form a cyclic anhydride" ... 

Many trivial names exist for acids these are listed in Table 1.11. Generally, radicals are formed by replacing -ic acid by -oyL When a trivial name is given to an acyclic monoacid or diacid, the numeral 1 is always given as locant to the carbon atom of a carboxyl group in the acid or to the carbon atom with a free valence in the radical RCO—. 

Ester interchange reactions are valuable, since, say, methyl esters of di-carboxylic acids are often more soluble and easier to purify than the diacid itself. The methanol by-product is easily removed by evaporation. Poly (ethylene terephthalate) is an example of a polymer prepared by double application of reaction 4 in Table 5.3. The first stage of the reaction is conducted at temperatures below 200°C and involves the interchange of dimethyl terephthalate with ethylene glycol... 

The diacid-diamine amidation described in reaction 2 in Table 5.4 has been widely studied in the melt, in solution, and in the solid state. When equal amounts of two functional groups are present, both the rate laws and the molecular weight distributions are given by the treatment of the preceding sections. The stoichiometric balance between reactive groups is readily obtained by precipitating the 1 1 ammonium salt from ethanol ... 

As with polyesters, the amidation reaction of acid chlorides may be carried out in solution because of the enhanced reactivity of acid chlorides compared with carboxylic acids. A technique known as interfacial polymerization has been employed for the formation of polyamides and other step-growth polymers, including polyesters, polyurethanes, and polycarbonates. In this method the polymerization is carried out at the interface between two immiscible solutions, one of which contains one of the dissolved reactants, while the second monomer is dissolved in the other. Figure 5.7 shows a polyamide film forming at the interface between an aqueous solution of a diamine layered on a solution of a diacid chloride in an organic solvent. In this form interfacial polymerization is part of the standard repertoire of chemical demonstrations. It is sometimes called the nylon rope trick because of the filament of nylon produced by withdrawing the collapsed film. 

The diphenyl ester of the diacid [XI] is used to prevent side reactions such as decarboxylation. 

In the area of moleculady designed hot-melt adhesives, the most widely used resins are the polyamides (qv), formed upon reaction of a diamine and a dimer acid. Dimer acids (qv) are obtained from the Diels-Alder reaction of unsaturated fatty acids. Linoleic acid is an example. Judicious selection of diamine and diacid leads to a wide range of adhesive properties. Typical shear characteristics are in the range of thousands of kilopascals and are dependent upon temperature. Although hot-melt adhesives normally become quite brittle below the glass-transition temperature, these materials can often attain physical properties that approach those of a stmctural adhesive. These properties severely degrade as the material becomes Hquid above the melt temperature. 

Standard polyester fibers contain no reactive dye sites. PET fibers are typically dyed by diffusiag dispersed dyestuffs iato the amorphous regions ia the fibers. Copolyesters from a variety of copolymeri2able glycol or diacid comonomers open the fiber stmcture to achieve deep dyeabiHty (7,28—30). This approach is useful when the attendant effects on the copolyester thermal or physical properties are not of concern (31,32). The addition of anionic sites to polyester usiag sodium dimethyl 5-sulfoisophthalate [3965-55-7] has been practiced to make fibers receptive to cationic dyes (33). Yams and fabrics made from mixtures of disperse and cationicaHy dyeable PET show a visual range from subde heather tones to striking contrasts (see Dyes, application and evaluation). 

Fluorinated ether-containing dicarboxyhc acids have been prepared by direct fluorination of the corresponding hydrocarbon (17), photooxidation of tetrafluoroethylene, or by fluoride ion-cataly2ed reaction of a diacid fluoride such as oxalyl or tetrafluorosuccinyl fluorides with hexafluoropropylene oxide (46,47). Equation 8 shows the reaction of oxalyl fluoride with HEPO. A difunctional ether-containing acid fluoride derived from HEPO contains regular repeat units of perfluoroisopropoxy group and is terminated by two alpha-branched carboxylates. 

Fluorinated diacids offer a convenient method for introducing a perfluoro moiety into organic molecules. They are of potential interest in the preparation of polyamides and other fluorinated polymers. A detailed description of the perfluorocarboxyUc acids and their derivatives has been pubflshed (1), and a review article on polyfluorinated linear biflmctional compounds has appeared (35). 

Cross-linked macromolecular gels have been prepared by Eriedel-Crafts cross-linking of polystyrene with a dihaloaromatic compound, or Eriedel-Crafts cross-linking of styrene—chloroalkyl styrene copolymers. These polymers in their sulfonated form have found use as thermal stabilizers, especially for use in drilling fluids (193). Cross-linking polymers with good heat resistance were also prepared by Eriedel-Crafts reaction of diacid haUdes with haloaryl ethers (194). 

Chemical Properties. Trimethylpentanediol, with a primary and a secondary hydroxyl group, enters into reactions characteristic of other glycols. It reacts readily with various carboxyUc acids and diacids to form esters, diesters, and polyesters (40). Some organometaUic catalysts have proven satisfactory for these reactions, the most versatile being dibutyltin oxide. Several weak bases such as triethanolamine, potassium acetate, lithium acetate, and borax are effective as stabilizers for the glycol during synthesis (41). 

A cross-linked and crystalline copoly(ester—imide) containing an alkene function was made by reaction of an unsaturated diacid chloride containing a cychc imido group with ethylene glycol at low temperature (27). 

New heat-resistant polymers containing -iiitrophenyl-substituted quinoxaline units and imide rings as well as flexible amide groups have been synthesi2ed by polycondensation reaction of a dianainoquinoxaline derivative with diacid dichlorides (80). These polymers are easily soluble in polar aprotic solvents with inherent viscosities in the range of 0.3—0.9 dL/g in NMP at 20°C. AH polymers begin to decompose above 370°C. 

A polyester backbone with two HFIP groups (12F aromatic polyester of 12F-APE) was derived by the polycondensation of the diacid chloride of 6FDCA with bisphenol AF or bisphenol A under phase-transfer conditions (120). These polymers show complete solubkity in THF, chloroform, ben2ene, DMAC, DMF, and NMP, and form clear, colorless, tough films the inherent viscosity in chloroform at 25°C is 0.8 dL/g. A thermal stabkity of 501°C (10% weight loss in N2) was observed. 

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