Caprolactam

Last updated
Caprolactam
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.

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]

Related Research Articles

<span class="mw-page-title-main">Nylon</span> Family of synthetic polymers originally developed as textile fibers

Nylon is a generic designation for a family of synthetic polymers composed of polyamides. Nylon is a silk-like thermoplastic, generally made from petroleum, that can be melt-processed into fibers, films, or shapes. Nylon polymers can be mixed with a wide variety of additives to achieve many property variations. Nylon polymers have found significant commercial applications in fabric and fibers, in shapes, and in films.

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

Petrochemicals are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as maize, palm fruit or sugar cane.

<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.

<span class="mw-page-title-main">Oxime</span> Organic compounds of the form >C=N–OH

In organic chemistry, an oxime is a organic compound belonging to the imines, with the general formula RR’C=N−OH, where R is an organic side-chain and R' may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. O-substituted oximes form a closely related family of compounds. Amidoximes are oximes of amides with general structure R1C(=NOH)NR2R3.

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

Hydroxylamine is an inorganic compound with the formula NH2OH. The material is a white crystalline, hygroscopic compound. 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.

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

Acrylic acid (IUPAC: propenoic acid) is an organic compound with the formula CH2=CHCOOH. It is the simplest unsaturated carboxylic acid, consisting of a vinyl group connected directly to a carboxylic acid terminus. This colorless liquid has a characteristic acrid or tart smell. It is miscible with water, alcohols, ethers, and chloroform. More than a million tons are produced annually.

Cyclohexene is a hydrocarbon with the formula C6H10. This cycloalkene is a colorless liquid with a sharp smell. It is an intermediate in various industrial processes. Cyclohexene is not very stable upon long term storage with exposure to light and air because it forms peroxides.

<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">Formamide</span> Chemical compound

Formamide is an amide derived from formic acid. It is a colorless liquid which is miscible with water and has an ammonia-like odor. It is chemical feedstock for the manufacture of sulfa drugs and other pharmaceuticals, herbicides and pesticides, and in the manufacture of hydrocyanic acid. It has been used as a softener for paper and fiber. It is a solvent for many ionic compounds. It has also been used as a solvent for resins and plasticizers. Some astrobiologists suggest that it may be an alternative to water as the main solvent in other forms of life.

A lactam is a cyclic amide, formally derived from an amino alkanoic acid through cyclization reactions. The term is a portmanteau of the words lactone + amide.

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

Cyclohexanone is the organic compound with the formula (CH2)5CO. The molecule consists of six-carbon cyclic molecule with a ketone functional group. This colorless oily liquid has an odor reminiscent of acetone. Over time, samples of cyclohexanone assume a pale yellow color. Cyclohexanone is slightly soluble in water and miscible with common organic solvents. Billions of kilograms are produced annually, mainly as a precursor to nylon.

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

Bromine pentafluoride, BrF5, is an interhalogen compound and a fluoride of bromine. It is a strong fluorinating agent.

<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.

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

Cyclohexanone oxime is an organic compound containing the functional group oxime. This colorless solid is an important intermediate in the production of nylon 6, a widely used polymer.

Commodity chemicals are a group of chemicals that are made on a very large scale to satisfy global markets. The average prices of commodity chemicals are regularly published in the chemical trade magazines and web sites such as Chemical Week and ICIS. There have been several studies of the scale and complexity of this market for example in the USA.

<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 N-hydroxy derivative of phthalimide. The compound can be utilized as a catalyst for oxidation reactions, in particular for the selective oxidation with molecular oxygen under mild conditions.

AdvanSix 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.
  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
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