Caprolactam, hydrolysis

Nylon-6, on the other hand, is made by the ring opening polymerization of caprolactam with water in a tubular VK column reactor [6-8]. The process consists of two main stages (i) caprolactam hydrolysis to aminocaproic... 

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)... 

In one process the resulting solution is continuously withdrawn and cooled rapidly to below 75°C to prevent hydrolysis and then further cooled before being neutralised with ammonia. After phase separation, the oil phase is then treated with trichlorethylene to extract the caprolactam, which is then steam distilled. Pure caprolactam has a boiling point of 120°C at 10 mmHg pressure. In the above process 5.1 tons of ammonium sulphate are produced as a by-product per ton of caprolactam. 

Important solvolysis reactions for nylons are hydrolysis, methanolysis, glycolysis, aminolysis, ammonolysis, transamidation, and acidolysis.17 Hydrolysis of nylon-6 with steam in the presence of an acid catalyst to form caprolactam is tlie preferred depolymerization approach. However, when recycling carpet face fibers, file fillers in the polymer may react with file acid catalyst and lower the efficiency of the catalyst. 

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]. 

The use is described of a process involving both hydrolysis and pyrolysis to recover caprolactam from nylon 6 used in carpet fibres. By means of precise temperature control and the use of a catalyst, nylon 6 can be isolated from the PP backing. The process has been developed by the National Renewable Resource Laboratory, and interest has been shown by AlliedSignal who are considering a cooperative research and development project. 

The high simple diastereoselectivities observed running the [4-1-3] cycloadditions raised the question concerning the induction of chirality. Preliminary experiments involving chiral menthyloxy Fischer carbenes 169 (R = (-)-men-thyl) resulted in the formation of the diastereomeric lactim ethers 173-1 and 173-2 in a 7 3 ratio, which could be separated by means of a crystallization. A final acidic hydrolysis gave the enantiomerically pure e-caprolactams 175 and ent-175 and the acyclic esters, respectively. No signs of racemization have been detected,Eqs. (18,19) [39b]. 

Caprolactam (5.68, Fig. 5.21) has a seven-membered lactam ring and is a major industrial compound in the production of Nylon , its polymer. This compound shows only moderate levels of toxicity in mice and rats when administered orally. The hydrolysis product 6-aminohexanoic acid (5.69) was a minor metabolite in rats [176]. Hydroxylation in the y-position to yield 5.70 without preliminary hydrolysis of the lactam linkage has been shown to be the major metabolic pathway. This metabolite hydrolyzes in urine to produce 6-amino-4-hydroxyhexanoic acid (5.71), which is in equilibrium with the corresponding lactone (5.72). 

Hydrolytic polymerization of e-caprolactam to form nylon 6 (Sec. 2-8f) is carried out commercially in both batch and continuous processes by heating the monomer in the presence of 5-10% water to temperatures of 250-270°C for periods of 12 h to more than 24 h [Anton and Baird, 2002 Zimmerman, 1988]. Several equilibria are involved in the polymerization [Bertalan et al., 1984 Sekiguchi, 1984]. These are hydrolysis of the lactam to e-amino-caproic acid (Eq. 7-56), step polymerization of the amino acid with itself (Eq. 7-57), and initiation of ring-opening polymerization of lactam by the amino acid. The amino acid is... 

The deoxygenative ring expansion of nitrobenzene with tri-n-butylphosphine in butanol (77BCJ2013), or with phosphorus trichloride and di-n-butylamine in hexane, followed by catalytic reduction and hydrolysis of the resulting 2-butoxy- or 2-butylamino-3//-azepines have been patented as methods for the production of caprolactam (78JAP(K)78132586, 77GEP2647936 respectively). 

Although there is some evidence for protonation of the amide at the carboxyl oxygen, there is no evidence which confines the protonation exclusively to this position and many of the kinetic results of earlier workers may be interpreted in terms of either kind of mechanism in particular the results of Farber and Brieux225 on the hydrolysis of 6-caprolactam in sulphuric acid fit equation (5 1) very well. 

Cyclic anhydrides react well with trimethyl(trifluoromethyl)silane however, a stoichiometric amount of tctrabutylammonium fluoride is required. - For example, succinic anhydride undergoes efficient addition of trimethyl(trifluoromethyl)silane to initially form an adduct, which upon hydrolysis aflbrds the trifluoromethyl-substiluted 0x0 carboxylic acid 27. Simple amides, such as benzamide and acetamide, do not react with trimetliyl(trifluoromethyl)silane even when a molar quantity of tetrabutylainmonium fluoride is used. Furthermore, lactams, such as caprolactam, do not react with trimethyl(trifluoromethyl)silane under similar conditions. An activated amide carbonyl, such as that in A -methylsuccinimide. however, reacts smoothly to afford an interesting adduct, which upon acid hydrolysis affords the hcmiaminal 28. 

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