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Caprolactam
Caprolactam-2D-skeletal.png
Caprolactam-3D-vdW.png
IUPAC name
Other names ε-Caprolactam, 1-Aza-2-cycloheptanone, 2-Azacycloheptanone, Capron PK4, Cyclohexanone iso-oxime, Extrom 6N, Hexahydro-2-azepinone, Hexahydro-2H-azepin-2-one (9CI), Hexanolactame
Identifiers
CAS number 105-60-2 Yes check.svgY
PubChem 7768
EC number 203-313-2
SMILES
Properties
Molecular formula C6H11NO
Molar mass 113.16 g/mol
Appearance white solid
Density 1,01 g/cm3
Melting point

68 °C

Boiling point

136-138 °C @ 10 mm Hg

Solubility in water 820 g/L (20 °C)
Hazards
R-phrases R20, R22, R36/37/38
Flash point 125 °C
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Caprolactam is an organic compound with the formula (CH2)5C(O)NH. This colourless solid, which is a lactam or a cyclic amide of caproic acid. Approximately 2 billion kilograms are produced annually. Caprolactam is the precursor to Nylon 6, a widely used synthetic polymer.[1]

Contents

Synthesis and production

Caprlactam was first described in the late 1800s when it was prepared by the cyclization of ε-aminocaproic acid, the product of the hydrolysis of caprolactam. Given the commercial significance of nylon-6, many methods have been developed for the production of caprolactam. Most of the caprolactam is synthesised from cyclohexanone, which is first converted to its oxime. Treatment of this oxime with acid induces the Beckmann rearrangement.

The Beckmann Rearrangement


The immediate product of the acid-induced rearrangement is the bisulfate salt of caprolactam. This salt is neutralized with ammonia to release the free lactam and cogenerate ammonium sulfate. In optimizing the industrial practices, much attention is directed toward minimizing the production of ammonium salts.

The other major industrial route involves formation of the oxime from cyclohexane using nitrosyl chloride. The advantage of this method is that cyclohexane is less expensive than cyclohexanone. In earlier times, caprolactam was prepared by treatment of caprolactone with ammonia.[1]

Uses

Caprolactam is the precursor to Nylon-6. The conversion entails a ring-opening polymerization:

n (CH2)5C(O)NH → [(CH2)5C(O)NH]n

Nylon-6 is widely used in fibers and plastics.

Safety

Caprolactam is an irritant and is mildly toxic, with an LD50 of 1.1 g/kg (rat, oral). In 1991, it was included on the list of hazardous air pollutants by the U.S. Clean Air Act of 1990. It was subsequently removed from the list in 1993.[2] In water, caprolactam hydrolyzes to aminocaproic acid, which is used medicinally.

References

  1. ^ a b Josef Ritz, Hugo Fuchs, Heinz Kieczka, William C. Moran "Caprolactam" Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. doi:10.1002/14356007.a05_031
  2. ^ EPA - Modifications To The 112(b)1 Hazardous Air Pollutants

Further information

  • The Nylon-6 Promotional Group website.[1]]
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