Caprolactam

Last updated
Caprolactam
Pytel na Caprolactam.jpg
Caprolactam-2D-skeletal.png
Caprolactam-from-xtal-3D-sf.png
Names
Preferred IUPAC name
Azepan-2-one
Other names
  • 1-Aza-2-cycloheptanone
  • 2-Azacycloheptanone
  • ε-Caprolactam
  • Capron PK4
  • Cyclohexanone iso-oxime
  • Extrom 6N
  • Hexahydro-2-azepinone
  • Hexahydro-2H-azepin-2-one (9CI)
  • Hexanolactam
  • Hexano-6-lactam
  • Aminocaproic lactam
Identifiers
3D model (JSmol)
106934
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.003.013 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 203-313-2
101802
KEGG
PubChem CID
UNII
  • InChI=1S/C6H11NO/c8-6-4-2-1-3-5-7-6/h1-5H2,(H,7,8) Yes check.svgY
    Key: JBKVHLHDHHXQEQ-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C6H11NO/c8-6-4-2-1-3-5-7-6/h1-5H2,(H,7,8)
    Key: JBKVHLHDHHXQEQ-UHFFFAOYAF
  • O=C1NCCCCC1
Properties
C6H11NO
Molar mass 113.160 g·mol−1
AppearanceWhite solid
Density 1.01 g/cm3
Melting point 69.2 °C (156.6 °F; 342.3 K)
Boiling point 270.8 °C (519.4 °F; 544.0 K) at 1013.25 hPa
866.89 g/l (22 °C)
Vapor pressure 8.10−8 mmHg (20°C) [1]
Hazards
GHS labelling:
GHS-pictogram-exclam.svg
Warning
H302, H315, H319, H332, H335
P261, P264, P270, P271, P280, P301+P312, P302+P352, P304+P312, P304+P340, P305+P351+P338, P312, P321, P330, P332+P313, P337+P313, P362, P403+P233, P405, P501
Flash point 125 °C (257 °F; 398 K)
Explosive limits 1.4%-8.0% [1]
NIOSH (US health exposure limits):
PEL (Permissible)
none [1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Caprolactam (CPL) is an organic compound with the formula (CH2)5C(O)NH. This colourless solid is a lactam (a cyclic amide) of caproic acid. Global demand for this compound is approximately five million tons per year, and the vast majority is used to make Nylon 6 filament, fiber, and plastics. [2]

Contents

Synthesis and production

Caprolactam 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. World demand for caprolactam was estimated to reach five million tons per year for 2015. 90% of caprolactam produced is used to make filament and fiber, 10% for plastics, and a small amount is used as a chemical intermediate. [2] Due to its commercial significance, many methods have been developed for the production of caprolactam. It was estimated that 90% of all caprolactam is synthesised from cyclohexanone (1), which is first converted to its oxime (2). Treatment of this oxime with acid induces the Beckmann rearrangement to give caprolactam (3): [2]

Beckmann-rearangement.png

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. [2]

The other major industrial route involves formation of the oxime from cyclohexane using nitrosyl chloride, and this method accounts for 10% of world production. [2] The advantage of this method is that cyclohexane is less expensive than cyclohexanone.

A minor industrial route involves the treatment of cyclohexanecarboxylic acid with nitrosylsulfuric acid (the Snia Viscosa process). This is thought to proceed via a ketene.

Nitrosodecarboxylation Caprolactam Synthesis.svg

Other paths to caprolactam include the depolymerization of waste Nylon 6, and the reaction of caprolactone with ammonia. [2] At bench scale, the reaction between cyclohexanone with hydrazoic acid to give caprolactam in the Schmidt reaction has been reported. [3]

Schmidt ring expansion.png

Uses

Almost all caprolactam produced goes into the manufacture of Nylon 6. The conversion entails a ring-opening polymerization:

Caprolactam polymerization.png

Nylon 6 is widely used in fibers and plastics.

In situ anionic polymerization is employed for cast nylon production where conversion from ε-caprolactam to Nylon 6 takes place inside a mold. In conjunction with endless fiber processing the term thermoplastic resin transfer molding (T-RTM) is often used.

Caprolactam is also used in the synthesis of several pharmaceutical drugs including pentylenetetrazol, meptazinol, and laurocapram.

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 1996 at the request of the manufacturers. [4] In water, caprolactam hydrolyzes to aminocaproic acid, which is used medicinally.

As of 2016 caprolactam had the unusual status of being the only chemical in the International Agency for Research on Cancer's lowest hazard category, Group 4: "probably not carcinogenic to humans". [5]

Currently, there is no official permissible exposure limit set for workers handling caprolactam in the United States. The recommended exposure limit is set at 1 mg/m3 over an eight-hour work shift for caprolactam dusts and vapors. The short-term exposure limit is set at 3 mg/m3 for caprolactam dusts and vapors. [6]

Climate impact

The production of caprolactam can produce nitrous oxide as a by-product, a highly potent greenhouse gas. Emissions differ significantly due to different production processes and inconsistent use of emission abatement technology. A study commissioned by the German Federal Ministry for Economic Affairs and Climate Action estimates emissions between 9 kg of nitrous oxide per ton of caprolactam and almost zero. [7]

Nitrous oxide emissions from caprolactam production are unregulated in most countries. Unlike other chemical production processes, nitrous oxide emissions from caprolactam production are not included in the European Union Emissions Trading System. [8]

Related Research Articles

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Phenol is an aromatic organic compound with the molecular formula C6H5OH. It is a white crystalline solid that is volatile. The molecule consists of a phenyl group bonded to a hydroxy group. Mildly acidic, it requires careful handling because it can cause chemical burns.

<span class="mw-page-title-main">Nitrous oxide</span> Colourless non-flammable greenhouse gas

Nitrous oxide, commonly known as laughing gas, nitrous, or factitious air, among others, is a chemical compound, an oxide of nitrogen with the formula N
2O. At room temperature, it is a colourless non-flammable gas, and has a slightly sweet scent and taste. At elevated temperatures, nitrous oxide is a powerful oxidiser similar to molecular oxygen.

<span class="mw-page-title-main">Petrochemical</span> Chemical product derived from petroleum

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<span class="mw-page-title-main">Butanone</span> Chemical compound

Butanone, also known as methyl ethyl ketone (MEK) or ethyl methyl ketone, is an organic compound with the formula CH3C(O)CH2CH3. This colorless liquid ketone has a sharp, sweet odor reminiscent of acetone. It is produced industrially on a large scale, but occurs in nature only in trace amounts. It is partially soluble in water, and is commonly used as an industrial solvent. It is an isomer of another solvent, tetrahydrofuran.

<span class="mw-page-title-main">Beckmann rearrangement</span> Chemical rearrangement

The Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann (1853–1923), is a rearrangement of an oxime functional group to substituted amides. The rearrangement has also been successfully performed on haloimines and nitrones. Cyclic oximes and haloimines yield lactams.

Acrylonitrile is an organic compound with the formula CH2CHCN and the structure H2C=CH−C≡N. It is a colorless, volatile liquid. It has a pungent odor of garlic or onions. Its molecular structure consists of a vinyl group linked to a nitrile. It is an important monomer for the manufacture of useful plastics such as polyacrylonitrile. It is reactive and toxic at low doses.

<span class="mw-page-title-main">Hydroxylamine</span> Inorganic compound

Hydroxylamine is an inorganic compound with the chemical formula NH2OH. The compound is in a form of a white hygroscopic crystals. Hydroxylamine is almost always provided and used as an aqueous solution. It is consumed almost exclusively to produce Nylon-6. The oxidation of NH3 to hydroxylamine is a step in biological nitrification.

Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is non-polar. Cyclohexane is a colourless, flammable liquid with a distinctive detergent-like odor, reminiscent of cleaning products. Cyclohexane is mainly used for the industrial production of adipic acid and caprolactam, which are precursors to nylon.

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<span class="mw-page-title-main">Cyclohexanol</span> Chemical compound

Cyclohexanol is the organic compound with the formula HOCH(CH2)5. The molecule is related to cyclohexane by replacement of one hydrogen atom by a hydroxyl group. This compound exists as a deliquescent colorless solid with a camphor-like odor, which, when very pure, melts near room temperature. Millions of tonnes are produced annually, mainly as a precursor to nylon.

<span class="mw-page-title-main">Adipic acid</span> Chemical compound

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<span class="mw-page-title-main">Cyclohexanone</span> Chemical compound

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<span class="mw-page-title-main">Caprolactone</span> Chemical compound

ε-Caprolactone or simply caprolactone is a lactone possessing a seven-membered ring. Its name is derived from caproic acid. This colorless liquid is miscible with most organic solvents and water. It was once produced on a large scale as a precursor to caprolactam.

<span class="mw-page-title-main">Nitrosyl chloride</span> Chemical compound

Nitrosyl chloride is the chemical compound with the formula NOCl. It is a yellow gas that is commonly encountered as a component of aqua regia, a mixture of 3 parts concentrated hydrochloric acid and 1 part of concentrated nitric acid. It is a strong electrophile and oxidizing agent. It is sometimes called Tilden's reagent, after William A. Tilden, who was the first to produce it as a pure compound.

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<span class="mw-page-title-main">Cyclohexanone oxime</span> Chemical compound

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<span class="mw-page-title-main">Laurolactam</span> Chemical compound

Laurolactam is an organic compound from the group of macrocyclic lactams. Laurolactam is mainly used as a monomer in engineering plastics, such as nylon-12 and copolyamides.

<i>N</i>-Hydroxyphthalimide Chemical compound

N-Hydroxyphthalimide is the organic compound with the formula C6H4(CO)2NOH. A white or yellow solid, it is a derivative of phthalimide. The compound is as a catalyst in the synthesis of other organic compounds. It is soluble in water and organic solvents such as acetic acid, ethyl acetate and acetonitrile.

AdvanSix Inc. is an American chemical company that produces nylon 6 and related chemicals such as caprolactam and ammonium sulfate fertilizers. It operated as Honeywell's Resins and Chemicals division until 2016, when it was spun off as a separate company. The unit accounted for 3 percent of Honeywell's sales at the time. For 2019, revenue is estimated at $1.4 billion. The company traces its lineage to the H. W. Jayne Company, established 1884 in Frankford, Pennsylvania.

References

  1. 1 2 3 NIOSH Pocket Guide to Chemical Hazards. "#0097". National Institute for Occupational Safety and Health (NIOSH).
  2. 1 2 3 4 5 6 Josef Ritz; Hugo Fuchs; Heinz Kieczka; William C. Moran. "Caprolactam". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a05_031.pub2. ISBN   978-3527306732.
  3. ↑ Eric J. Kantorowski; Mark J. Kurth (2000). "Expansion to Seven-Membered Rings". Tetrahedron. 56 (26): 4317–4353. doi:10.1016/S0040-4020(00)00218-0.
  4. ↑ EPA - Modifications To The 112(b)1 Hazardous Air Pollutants
  5. ↑ "Agents Classified by the IARC Monographs" (PDF). International Agency for Research on Cancer. February 22, 2016. p. 395. Retrieved 21 October 2016.
  6. ↑ NIOSH Pocket Guide to Chemical Hazards, CDC, retrieved November 8, 2013
  7. ↑ "Mitigation potentials for emissions of nitrous oxide from chemical industry in industrialised countries world-wide" (PDF). Öko-Institut. March 2023. Retrieved 2023-10-17.
  8. ↑ Böck, Hanno (2023-09-28). "The avoidable Super-Greenhouse-Gas from Fertilizer, Nylon, and Vitamin B3 production". Industry Decarbonization Newsletter. Retrieved 2023-10-17.
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