Caprolactam Specifications

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. 

Enzymatic hydrolysis is also used for the preparation of L-amino acids. Racemic D- and L-amino acids and their acyl-derivatives obtained chemically can be resolved enzymatically to yield their natural L-forms. Aminoacylases such as that from Pispergillus OTj e specifically hydrolyze L-enantiomers of acyl-DL-amino acids. The resulting L-amino acid can be separated readily from the unchanged acyl-D form which is racemized and subjected to further hydrolysis. Several L-amino acids, eg, methionine [63-68-3], phenylalanine [63-91-2], tryptophan [73-22-3], and valine [72-18-4] have been manufactured by this process in Japan and production costs have been reduced by 40% through the appHcation of immobilized cell technology (75). Cyclohexane chloride, which is a by-product in nylon manufacture, is chemically converted to DL-amino-S-caprolactam [105-60-2] (23) which is resolved and/or racemized to (24)... 

Camphor, molecular model of, 129 specific rotation of, 296 Cannizzaro, Stanislao, 724 Cannizzaro reaction. 724 mechanism of, 724 Caprolactam, nylon 6 from, 1213 Capsaicin, structure of. 78 -curbahlehyde, aldehyde name ending, 696... 

The caprolactam obtained must meet die specifications of permanganate number, volatile bases, hazen color, UV transmittance, solidification point, and turbidity in order to be used for repolymerization alone or in combination witii virgin CL.5 Reported CL purification methods include recrystallization, solvent extraction, and fractional distillation. One solvent extraction technique involves membrane solvent extraction. Ion exchange resins have been shown to be effective in the purification of aqueous caprolactam solutions. In one such process,... 

Racemic a-amino amides and a-hydroxy amides have been hydrolyzed enantio-selectively by amidases. Both L-selective and o-selective amidases are known. For example, a purified L-selective amidase from Ochrobactrum anthropi combines a very broad substrate specificity with a high enantioselectivity on a-hydrogen and a,a-disubstituted a-amino acid amides, a-hydroxyacid amides, and a-N-hydroxya-mino acid amides [102]. A racemase (a-amino-e-caprolactam racemase, EC 5.1.1.15) converts the o-aminopeptidase-catalyzed hydrolysis of a-amino acid amides into a DKR (Figure 6.38) [103]. 

Rhodium carboxylates have been found to be effective catalysts for intramolecular C—H insertion reactions of a-diazo ketones and esters.215 In flexible systems, five-membered rings are formed in preference to six-membered ones. Insertion into methine hydrogen is preferred to a methylene hydrogen. Intramolecular insertion can be competitive with intramolecular addition. Product ratios can to some extent be controlled by the specific rhodium catalyst that is used.216 In the example shown, insertion is the exclusive reaction with Rh2(02CC4F9)4, whereas only addition occurs with Rh2(caprolactamate)4, which indicates that the more electrophilic carbenoids favor insertion. 

The student should adapt this general mechanism and work through the specific cyclic example of cyclohexanone oxime to caprolactam. Note that the result of the shift is an expansion of the ring size in the final amide product with the incorporation of the nitrogen atom as part of the ring. 

Among the more common thermoplastics from ring opening polymerization of interest in composite processing are polylactams, polyethers, polyacetals, and polycycloolefins. It has also been shown that polycarbonates can be produced from cyclic carbonates [22], Anionic ring opening polymerization of caprolactam to nylon 6 is uniquely suited to form a thermoplastic matrix for fiber-reinforced composites, specifically by the reaction injection pultrusion process [23-25]. The fast reaction kinetics with no by-products and the crystalline... 

The specific heat of E glass fiber is 0.192 cal/gm K (i.e., 0.804 J/gm K) [73]. The specific heat of caprolactam as a function of temperature was fitted to the following equation from experimental data available in Monsanto ... 

Alternative purification protocols are available. Zhaolin Sun of Lanzhou University reports (Tetrahedron Lett. 45 2681,2004) that the ionic liquid TISC was specifically designed to promote Beckmann rearrangement. TISC is not soluble in water, so the product caprolactam was easily removed from the ionic liquid by extraction with water. 

Figure 17.17. Examples of reactors for specific liquid-gas processes, (a) Trickle reactor for synthesis of butinediol 1.5 m dia by 18 m high, (b) Nitrogen oxide absorption in packed columns, (c) Continuous hydrogenation of fats, (d) Stirred tank reactor for batch hydrogenation of fats, (e) Nitrogen oxide absorption in a plate column, (f) A thin film reactor for making dodecylbenzene sulfonate with S03. (g) Stirred tank reactor for the hydrogenation of caprolactam, (h) Tubular reactor for making adiponitrile from adipic acid in the presence of phosphoric acid.

To establish the identity of the —CO—NH— links, a comparative recording was made between 2000 and 4000 cm-1, a range that is specific for those groups. Samples of pure poly (e-caprolactam) and a copolymer synthesized mechanochemically were used. The reaction time exerted a decisive influence on the polymer structure. The products obtained after short milling times (less than 20 hours) gave bands characteristic of the support polymer and a succession of new bands... 

A typical loss maximum of this type was observed for poly(methyl methacrylate) containing caprolactam or derivatives of cyclohexane12,13. It is noteworthy70 that in the latter case the relaxation induced by the cyclohexyl group present in the incorporated plasticizer and the secondary relaxation of poly(cyclohexyl methacrylate) or poly(cyclohexyl acrylate) are characterized by an identical temperature position, 190 K (1 Hz), and activation energy, 47.9 kJ/mol (AU = 47.7 kJ/mol is reported for the chair-chair transition of cydohexanol). Hence, it can be seen that the cyclohexyl ring inversion, which represents a specific molecular motion, is remarkably insensitive to the surrounding molecules. 

The one-base mechanism is characterized by the retention of the substrate-derived proton in the product (internal retum).30) With this criterion, reactions catalyzed by a-amino-c-caprolactam racemase,323 amino acid racemase of broad specificity from Pseudomonas striata333 have been considered to proceed through the one-base mechanism. However, such internal returns were not observed in the reactions of alanine racemases from K coli B,33) B. stearothermophilus,263 and S. typhirmaium (DadB and /1/r).263 The internal return should not be observed in the two-base mechanism, because the base catalyzing the protonation to the intermediate probably obtains the proton from the solvent. But the failure of the observation of the internal return can be also explained by the single-base mechanism in which exchange of the proton abstracted from the substrate a-carbon with the solvent is much faster than its transfer to the a-carbanion. Therefore, lack of the internal return does not directly indicate the two-base mechanism of the alanine racemase reaction. 

The fused azepine 29 was formed unexpectedly by the cyclisation of the Al-arylsulfonyl caprolactam 28 as a competing reaction for the formation of the alkcnylphosphonite 30 <07OBC3472>. The cyclisation was also specific for the seven-membered derivatives, with pyrrolidinone and piperidinone derivatives yielding the phosphonites as the only products. The mechanism is believed to be initial ortho-lithiation followed by nucleophilic addition to the lactam followed by dehydration. 

Some pyrolysis products have high value. These are mainly monomers, such as methylmethacrylate, caprolactam (the monomer of PA 6), tetralinorethylene, or styrene. Others are comparable to standard prodncts with specifications of naphtha, kerosene, or gas-oil. Snch fractions have a well-known market, as follows from Table 1.7. 

The work [9] discusses publications analysing physico-chemical indices and the specifics of the chemical structure of cast aminoplasts modified with 20-50% (with respect to the mass of melamine) of caprolactam and other lactams. Materials of this type, havin an increased impact strength, thermal stability, strength and elasticity modulus in bending, are manufactured in Czechoslovakia under the trade mark UmaLur MK-1, MK-2, MK-3. 

A second type of study that corroborates the basic assumption is any measurement which specifically shows that the H bonded species are cyclic. Infrared data can offer such evidence, provided the only important species over a wide concentration range are monomers and dimers. For such a system the peak intensities of absorption by the monomer (Im) and dimer (Id) are simply related the ratio IdIIm is a constant. Such behavior has been observed and cited in favor of cyclic dimers of S-valerolactam and of -caprolactam by Tsuboi (2050), and of y-bu-tyrolactam by Klemperer et al. (1117). However, no such deduction can be made for other amides (e.g., see 1117), phenols (e.g., see 411), or alcohols (e.g., see 1375 and 1150). There is much evidence in favor of cyclic dimers of carboxylic acids in the gas phase (1081), and some referring to solutions (1652 and 445). On the other hand, the IR data for liquid formic acid are more complicated. Ghapman (373) concludes that the liquid contains a mixture of cyclic dimers and chain polymers. Dielectric data have been interpreted to show that formic acid is not entirely dimeric (1046). By use of thermo-electric osmometry Davies and Thomas have measured AH of dimerization of several amides and have concluded that trichloroacetamide and A -methyltrichloroacet-amide form cyclic dimers, whereeis iV-methylaceteunide, iV-methylform-... 

Skuratov et al. [39] tried to estimate the polymerization entropy from specific heat measurements of the monomer and polymer. However, the calculated value of AS29 8> -g- foi caprolactam (+1.1 eu), is too positive because the authors disregarded the fact that the polymer was not completely crystalline. Making allowance for the partial crystallinity, the value of ASp becomes more negative and approaches the value —3.2 eu calculated from the monomer-polymer equilibria [45]. 

The specific role of either amine or carboxyl groups in the polyaddition reaction has been established by Heikens et al. [216] by following the incorporation of added amine or carboxylic acid during the hydrolytic caprolactam polymerization. These experiments revealed that the lactam is added at the amine end group and that the reaction is catalysed by carboxyl groups. 

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