Caprolactam complexes

The related dirhodium(II) a-caprolactamate (cap) complex [Rh2(p--cap)4] undergoes a one-electron oxidation process at quite a lower potential (11 mV) than the acetate complex (1170 mV). In agreement with the Kochi hypothesis, the a-caprolactamate complex has recently been found to be an exceptional catalyst for the allylic oxidation of alkenes under mild conditions. A wide range of cyclohexenes, cycloheptenes, and 2-cycloheptenone (Eq. 5) are rapidly converted to enones and enediones in 1 h with only 0.1 mol % of [Rh2( x-cap)4] and yields ranging from 60 to 90%, in the presence of potassium carbonate [34]. 

D-a-Amino-e-caprolactam Complex of L-substrate L-a-Amino-e-caprolactam [177]... 

The crystal structures of the apo form and e-caprolactam complexed form of ACL racemase were solved at resolutions 2.21 A and 2.40 A, respectively [26]. The structure of ACL racemase was found to be composed of an N-terminal domain (residues 3 3), C-terminal domain (residues 321 36), and large PLP-binding domain (residues 48-319) (Figure 19.6). PLP boimd in a cleft between these domains, and the C4 atom of PLP connected covalently to the e-amino group of Lys267 to form the internal aldimine (Schiff base) linkage. 

Caprolactam is an amide and, therefore, undergoes the reactions of this class of compounds. It can be hydrolyzed, Ai-alkylated, O-alkylated, nitrosated, halogenated, and subjected to many other reactions (3). Caprolactam is readily converted to high molecular weight, linear nylon-6 polymers. Through a complex series of reactions, caprolactam can be converted to the biologically and nutritionally essential amino acid L-lysine (10) (see Amino acids). 

The preparation of nylon resins from lactam precursors involves ring opening, which is facihtated by a controlled amount of water in the reaction mixture. The salt complex condenses internally to produce the polyamide (57). The synthesis of nylon-6 [25038-54-4] from S-caprolactam is as follows ... 

A regio- and stereoselective Beckmann rearrangement utilized diastereose-lective host guest interactions of the inclusion complexes 225 and 228 in a solid state reaction. Initially, a 1 1 mixture of the chiral host 223 and the racemic oximes 224 and 227, respectively, was treated with ultra sound in the solid state to induce the optical resolution. Then H2SO4 was added to start the Beckmann rearrangement, the corresponding c-caprolactams 226 and 229 were isolated in 68 % and 64 % yields and ee of about 80 % and 69 % (determined by HPLC analysis on chiracel OC) (Scheme 43) [46]. 

Lactams Lactams represent a special type of C=N system due to the tautomerization between the lactam (keto amine) and lactim (hydroxyimine) forms. The lactim form is much more favored for cyclic than for non-cyclic amides of carbocyclic acids. In the reaction of complex 2b with N-methyl-e-caprolactam, a simple ligand exchange reaction occurs and complex 87 can be isolated. With P-propiolactam, the alkenyl-amido complex 88 is formed, which indicates an agostic interaction. The reaction of complex 1 with e-caprolactam gives, after elimination of the alkyne and of molecular hydrogen, complex 89 with a deproto-nated lactam in a r]2-amidate bonding fashion [47]. 

Production processes for chemical commodities exist often already for decades and are continuously enhanced as shown in the following example from the 1970s. Commodity production processes this time already have been rather complex composed by multiple reactions and interim steps as shown in the following example of Caprolactam production, an intermediate product for Polyamide (Sittig 1972, p. 139) in fig. 35. 

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]. 

Figure 1.13 Isothermal complex viscosity rise during anionic polymerization of caprolactam using caprolactam-magnesium-bromide/isophthaloyl-bis-caprolactam as the catalyst/initiator system. Run numbers and polymerization temperatures are shown in the legend...

Upon mixing and injection of the caprolactam monomer streams into the rheological instrument, polymerization was initiated and continued, whereas simultaneously monitoring the complex viscosity and other rheological parameters of the polymerizing system. The maximum measurable complex viscosity levels were achieved in about 100 s or less, depending on temperature. 

For sodium/hexamethylene-l,6-bis-carbamidocaprolactam system, Sibal et al. [64] found the value of the constant k in Equation 1.4 to be 17.5. Note that the values of the constant k in Equation 1.4 that defines the relative complex viscosity rise during anionic ring opening polymerization of caprolactam are comparable for both caprolactam-magnesium-bromide/isophthaloyl-bis-caprolactam and sodium/hexamethylene-l,6-bis-carbamidocapro-lactam as the catalyst/initiator systems even though the kinetic constants for anionic polymerization for these systems are extremely different (see Table 1.2). 

From Equation 1.4, the complex viscosity at 57 percent conversion of the caprolactam monomer, which may be defined as solidification or gel point, is 100Pas (1000 Poise). Combining the information on conversion at the gel point with the data presented in Figures 1.20 and 1.21, the time to gel formation during pultrusion can be estimated. 

The rheokinetics of polycaprolactam polymerizing in the monomer shows that below 50 percent conversion, the relative complex viscosity versus conversion of the nylon 6 homopolymerization is defined by the phenomenological equation ri / t]Q = exp(19.6 X), where // is the complex viscosity of nylon 6 anionically polymerizing in its monomer, 0 is the viscosity of caprolactam monomer, and X is fractional conversion. 

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