2183-86-0

Usage

General Description

2H-Azepin-2-one, 1,3-dihydro- is a chemical compound with the molecular formula C6H9NO. Also known as caprolactam, it is a cyclic amide with a seven-membered ring structure. Caprolactam is an important precursor in the production of nylon-6, a widely used synthetic polymer. It is primarily utilized in the production of nylon fibers, which are used in a range of applications including textiles, car parts, and packaging materials. Additionally, caprolactam is used in the production of other chemicals, such as polyurethanes and plasticizers. It is an important industrial chemical with versatile applications in various industries.

Upstream product

• 31162-13-7 2-azidobenzoic acid 
• 64-17-5 ethanol 
• 64-19-7 acetic acid 
• 622-37-7 Phenyl azide 

Downstream Products

• 2183-99-5 cis-2-azabicyclo<3.2.0>heptan-3-one 

Relevant academic research and scientific papers

Acid-base properties of arylnitrenium ions

This study uses a combination of laser flash photolysis (LFP) and product analysis to show that singlet nitrenes from the irradiation of phenyl, 4-biphenylyl, and 2-fluorenyl azide can be trapped by protonation in aqueous solutions forming nitrenium ions. With phenyl azide, the phenylnitrenium ion is indicated by the formation of ring-substituted anilines in yields of up to 50% in 1 M acids. The acidity dependence furnishes the ratio k(H):k(exp) = 1.1, where k(H) refers to H+-trapping of singlet phenylnitrene and k(exp) to ring expansion of this species. With k(H) expected to be 2-4 x 1010 M-1 s-1, k(exp) is therefore estimated as 2-4 x 1010 s-1. Protonation by solvent water also occurs, but even though the rate constant is of the order of 109 s-1, it constitutes a minor pathway in competition with the ring expansion. LFP studies in acids reveal a transient that is assigned the structure of N-protonated 4-hydroxy-2,5-cyclohexadienone imine, the intermediate formed by water addition to the para position of the phenylnitrenium ion. With 4-biphenylyl- and 2-fluorenylnitrene, ring expansion (and intersystem crossing) occurs more slowly and protonation by water is faster, with the consequence that there are substantial yields of nitrenium ion without added acids. These nitrenium ions are detected with ns LFP, and their formation from singlet nitrene is observed with ps LFP. Combining the LFP experiments with product analysis furnishes a pK(a) value of 16 for the 4-biphenylylnitrenium ion deprotonating to singlet nitrene in 20% acetonitrile. Thus singlet 4-biphenylylnitrene falls close to the category of a strong base in this solution. LFP experiments in acids show behavior consistent with N-protonation of the nitrenium ion forming an aniline dication. Kinetic analyses furnish pK(a) values of 0.1 (4-aminobiphenyl dication) and 0.6 (2-aminofluorene dication) in 20% acetonitrile with 1 M ionic strength. This and other pieces of evidence are consistent with these arylnitrenium ions being better regarded as 6-iminocyclohexadienyl carbocations. Overall, arylnitrenium ions (ArNH+) are very weak acids in water in their deprotonation to singlet nitrenes. They are also weak bases, accepting a proton to form the aniline dication - 1ArN ? 1ArNH+ ? (ArNH2)2+.

3H-azepines and related systems. Part 4. Preparation of 3 H-azepin-2-ones and 6H-azepino[2,1-b]quinazolin-12-ones by photo-induced ring expansions of aryl azides

Photolysis of a series of p-substituted phenyl azides (p-X-C6H4N3; X= CO2Me, CO2Et, CN, CF3, SO2NH2, CO2CHPh2, COMe, CHO, and NO2) in 1:1 (v/v) THF-water solution produces, in the majority of cases, a 5-substituted-3H-azepine-2-one. In a like manner, 3H-azepin-2-one-3-carboxylates can be prepared from 5-substituted-2-azidobenzoates, providing the 5-substituent is electron-withdrawing. 3H-Azepin-2-one mono- and di-carboxylic acids, the former in admixture with decarboxylated material, and 6H-azepino[2,1-b]quinazolin-12-ones, are obtained by irradiation of 2-azidobenzoic acid and of 5-azidoisophthalic acid, respectively. The mode of formation of the azepino-quinazolinones is discussed.

Photolysis and Thermolysis of Phenyl Azide in Acetic Acid. Trapping of 1-Azacyclohepta-1,2,4,6-tetraene and Nucleophilic Aromatic Substitution

Photolysis and thermolysis of phenyl azide in acetic acid yielded 1H-azepin-2(3H)-one (4), 2-methylbenzoxazole (15), 2- and 4- acetamidophenyl acetates (16) and (12), 2- and 4- acetamidophenols (14) and (13), acetanilide, and azobenzene.Addition of ethanol to the system caused a linear decrease in the yield of (4) and a more remarkable decrease in total yield for the para-products than that for the ortho-products to give 2- and 4- acetamidophenyl ethyl ethers (9) and (8).Photolysis of the azide in ethanol in the presence of phenol afforded 2-phenoxy-3H-azepine (5) and aniline, but no 2- and 4-phenetidines.The yield of compounds (4) and (12)-(16) was independent of the presence of penta-1,3-diene(0.01 M), and somewhat decreased by an addition of bromobenzene.The rate of decomposition of azide in acetic acid was not accelerated as compared with that in 1,4-dioxan, and the activation parameters varied little in the two solvents.The results suggest that 1-azacyclohepta-1,2,4,6-tetraene (1) formed via singlet phenylnitrene or via singlet excited phenyl azide is trapped by acetic acid or phenol to give (4) or (5), and that a resonance-stabilized ion (3) neighbouring acetate anion is formed by an attack of the singlet nitrene on acetic acid to give aromatic nucleophilic substitution.

Photolysis and Thermolysis of Phenyl Azide in Acetic Acid

The photolysis and thermolysis of phenyl azide in acetic acid gave 2,3-dihydro-1H-azepin-2-one via 1-azacyclohepta-1,2,4,6-tetraene, and ring-disubstituted products via a resonance-stabilized ion formed by attack of singlet phenylnitrene on acetic acid.