Caprolactam, reduction

C, b.p. 81"C. Manufactured by the reduction of benzene with hydrogen in the presence of a nickel catalyst and recovered from natural gase.s. It is inflammable. Used as an intermediate in the preparation of nylon [6] and [66] via caprolactam and as a solvent for oils, fats and waxes, and also as a paint remover. For stereochemistry of cyclohexane see conformation. U.S. production 1980 1 megatonne. 

The only other nitroparaffin manufactured on a large scale was nitrocyclohexane [1122-60-7] made by Hquid-phase nitration of cyclohexane. Nitrocyclohexane was the starting material for S-caprolactam via reduction to cyclohexanone oxime. This process has been superseded by other, more efficient processes (see Caprolactam). Nitrocyclohexane is not being produced ia large quantities for either captive use or sale. 

Hydroxylamine sulfate is produced by direct hydrogen reduction of nitric oxide over platinum catalyst in the presence of sulfuric acid. Only 0.9 kg ammonium sulfate is produced per kilogram of caprolactam, but at the expense of hydrogen consumption (11). A concentrated nitric oxide stream is obtained by catalytic oxidation of ammonia with oxygen. Steam is used as a diluent in order to avoid operating within the explosive limits for the system. The oxidation is followed by condensation of the steam. The net reaction is... 

Action of catalytic amounts of vanadium compounds on oxaziridine (52) yields caprolactam almost quantitatively. Reductive opening of the oxaziridine ring and /3-scission yield radical (118), which recyclizes with elimination of the metal ion to form the lactam (63) (77JPR274). 

Under forced conditions, the reductive cyclization of a 6-oximeester at 150 °C gave a simple c-caprolactam in about 60% yield [5a]. A preliminary chemoen-... 

Methoxyphenylurea, 31,10,13 Methyl -acetylbenzoate, 32, 81 Methyl acrylate, 30, 65 32, 86 y-Methylallophanate, 32, 62 Methylamine, 30, 60 4 -Methyl-2-aminobenzophenone, 32,12 N-Methylaniline, 30, 62 31,110 N-Methylarylamines, preparation by reductive alkylation, 30, 59, 60 Methylation, of e-caprolactam, 31, 72 of quinacetophenone, with dimethyl sulfate, 31, 91 with methyl iodide, 31, 90 2-Methyl-3,l,4-benzoxaz-4-one, 32, 12 N-Methyl-a-bromo-n-butyranilide, 30, 63... 

Reduction of 5,5-dimethyl-2-pyrrolidone with 3 mol of lithium aluminum hydride by refluxing for 8 hours in tetrahydrofuran gave 2,2-dimethylpyrrol-idine in 67-79% yields [1123]. Reduction of e-caprolactam was accomplished by heating with sodium bis(2-methoxyethoxy)aluminum hydride [544], by successive treatment with triethyloxonium fiuoroborate and sodium borohydride [1121], and by refluxing with borane-d ras. )a.y sulfide complex [1064]. 

Pyrrolidone is a lactone used for the production of nylon-4. This reactant may be produced by the reduction ammoniation of maleic anhydride. s-Caprolactam, used in the production of nylon-6, may be produced by the Beckman rearrangement of cyclohexanone oxime (structure 17.11). The oxime may be produced by the catalytic hydrogenation of nitrobenzene, the photolytic nitrosylation of cyclohexane (structure 17.9), or the reaction of cyclohexanone and hydroxylamine (structure 17.10). Nearly one-half of the production of caprolactam is derived from phenol. 

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). 

The TS-l catalyzed hydroxylation of phenol to a 1 1 mixture of catechol and hydroquinone has already been commercialized by Enichem. Another reaction of considerable commercial importance is the above mentioned ammoximation of cyclohexanone to cyclohexanone oxime66, an intermediate in the manufacture of caprolactam. It could form an attractive alternative to the established process that involves a circuitous route via oxidation of ammonia to nitric acid followed by reduction of the latter to hydroxylamine (figure 4). 

The most simple way of preparing sodium caprolactam consists in dissolving the sodium metal in molten caprolactam. Although the solutions thus obtained are capable to induce a rapid polymerization, we meet with complications arising from the presence of reduction products formed such as hexamethyleneimine (53,69,80,81) and 6-aminohexanol (59,69). These by-products affect the course of the subsequent polymerization as they react with the active centers. The ratio neutralization/reduction in the alkali metal reaction with caprolactam depends strongly on the temperature. According to Hamann (41) and Yumoto (101) the reduction reaction takes place to 75% and 10—20% respectively. In order to suppress the reduction it is recommended to maintain the temperature during the dissolution of the sodium metal below 100° (42). 

During a study of the e-caprolactam polymerization mechanism in isothermal conditions,1,2 it was found that there was a distinct induction period at the beginning of the process when sodium caprolactam salt was used as a catalyst. The addition of the necessary quantity of an activator into the reactive mixture leads to a reduction of the induction period and thus allows us to regulate the process rate. 

The hetero Diels-Alder reaction of y-dienyl N-acylazo compounds, formed by oxidation of the hydrazine derivative 25, yields bicyclic diazepines 26 in excellent yields. The reductive cleavage of the N-N bond yielded 6-substituted caprolactams 27 <07JOC6816>. 

ALTAM A process for making caprolactam from butadiene and carbon monoxide. Developed by DSM in the late 1990s and subsequently improved by Shell Chemicals, which contributed catalyst know-how. In the first two steps of the process, butadiene undergoes two hydroformylations with carbon monoxide, followed by reductive animation with ammonia and then cyclization to caprolactam. First commercialization was expected in Taiwan. A joint venture with Chiyoda Corporation, to further develop and commercialize the process, was announced in 2002. 

Although NH2OH can act as an oxidizing agent, it is usually used as a reductant. Its main use is in synthesis of caprolactam and oxime derivatives, but it is also used as an 02 scavenger. 

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