Azodicarbonamide

Last updated

Contents

Azodicarbonamide
Azodicarbonamide.png
Azodicarbonamide 3D spacefill.png
Names
IUPAC name
Carbamoyliminourea
Other names
  • Azodicarboxamide
  • Azobisformamide
  • C,C'-Azodi(formamide)
  • Diazenedicarboxamide
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.004.229 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 204-650-8
E number E927a (glazing agents, ...)
PubChem CID
UNII
  • InChI=1S/C2H4N4O2/c3-1(7)5-6-2(4)8/h(H2,3,7)(H2,4,8)/b6-5+ Yes check.svgY
    Key: XOZUGNYVDXMRKW-AATRIKPKSA-N Yes check.svgY
  • InChI=1/C2H4N4O2/c3-1(7)5-6-2(4)8/h(H2,3,7)(H2,4,8)/b6-5+
    Key: XOZUGNYVDXMRKW-AATRIKPKBW
  • O=C(/N=N/C(=O)N)N
Properties
C2H4N4O2
Molar mass 116.080 g·mol−1
AppearanceYellow to orange/red crystalline powder
Melting point 225 °C (437 °F; 498 K) (decomposes)
Hazards
GHS labelling:
GHS-pictogram-silhouette.svg
Danger
H242, H331, H334
NFPA 704 (fire diamond)
NFPA 704.svgHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
1
0
Safety data sheet (SDS)
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 ?)

Azodicarbonamide, ADCA, ADA, or azo(bis)formamide, is a chemical compound with the molecular formula C2H4O2N4. [1] It is a yellow to orange-red, odorless, crystalline powder. It is sometimes called a 'yoga mat' chemical because of its widespread use in foamed plastics. [2] [3] It was first described by John Bryden in 1959. [4]

Synthesis

It is prepared in two steps via treatment of urea with hydrazine to form biurea, as described in this idealized equation:

2 O=C(NH2)2 + H2N−NH2 → H2N−C(=O)−NH−NH−C(=O)−NH2 + 2 NH3

Oxidation with chlorine or chromic acid yields azodicarbonamide:

H2N−C(=O)−NH−NH−C(=O)−NH2 + Cl2 → H2N−C(=O)−N=N−C(=O)−NH2 + 2 HCl

Applications

Blowing agent

The principal use of azodicarbonamide is in the production of foamed plastics as a blowing agent. The thermal decomposition of azodicarbonamide produces nitrogen, carbon monoxide, carbon dioxide, and ammonia gases, which are trapped in the polymer as bubbles to form a foamed article. [5]

Azodicarbonamide is used in plastics, synthetic leather, and other industries and can be pure or modified. Modification affects the reaction temperatures. Pure azodicarbonamide generally reacts around 200 °C. In the plastic, leather, and other industries, modified azodicarbonamide (average decomposition temperature 170 °C) contains additives that accelerate the reaction or react at lower temperatures. [5]

An example of the use of azodicarbonamide as a blowing agent is found in the manufacture of vinyl (PVC) and EVA-PE foams, where it forms bubbles upon breaking down into gas at high temperature. Vinyl foam is springy and does not slip on smooth surfaces. It is useful for carpet underlay and floor mats. Commercial yoga mats made of vinyl foam have been available since the 1980s; the first mats were cut from carpet underlay. [6]

Food additive

As a food additive, azodicarbonamide is used as a flour bleaching agent and a dough conditioner. [7] It reacts with moist flour as an oxidizing agent. [8] The main reaction product is biurea, which is stable during baking. [8] Secondary reaction products include semicarbazide and ethyl carbamate. [7] It is known by the E number E927. Many restaurants in the US fast food industry removed the additive in response to negative publicity. [9]

Safety and regulation

Occupational (inhalation)

In a 1999 report, the World Health Organization has linked exposure to azodicarbonamide at workplaces where it is manufactured or handled in raw form to "respiratory issues, allergies and asthma". The available data are restricted to these occupational environments. Exposure of the general public to azodicarbonamide could not be evaluated because of the lack of available data. [10] The WHO concluded, "The level of risk is uncertain; hence, exposure levels should be reduced as much as possible".

In the UK, the Health and Safety Executive has identified azodicarbonamide as a respiratory sensitizer (a possible cause of asthma) in workplace settings and determined that containers of it should be labeled with "May cause sensitisation by inhalation." [11] Azodicarbonamide was added to the REACH Regulation candidate Substances of Very High Concern list in 2012, for its respiratory sensitizing properties. [12]

Food (ingestion)

In some jurisdictions, the use of azodicarbonamide as a flour bleaching agent has been phased out. For example, it is no longer authorized for use in Australia and the European Union as a food additive. [13] [14] Azodicarbonamide as a blowing agent in plastics has been banned in the European Union since August 2005 for the manufacture of plastic articles that are intended to come into direct contact with food. [15] In the United States, azodicarbonamide has a generally recognized as safe (GRAS) status and is allowed to be added to flour at levels up to 45 ppm. [16] [13] However, use in products intended for human consumption is in decline under pressure of the public opinion. [9] In 2014, amid public discomfort with the dual uses of azodicarbonamide, the sandwich franchise Subway and hamburger franchise Wendy's announced that they would no longer use it as a dough conditioner. [17] As of February 2014, the Center for Science in the Public Interest stated azodicarbonamide "has been poorly tested" and advocates for reducing the amount of azodicarbonamide that is allowed to be used in food. [17]

The ban on ADA in food is mostly motivated by the weak carcinogenic property of semicarbazide, a side product of ADA use. [15] The EU banned ADA in food containers despite an EFSA report considering such exposure "not a concern" due to low levels produced. The FDA's review maintains that ADA is safe at amounts allowed. [7]

As of February, 2021, in contrast to direct competitors like Wendy's that have phased out the ingredient, A&W continues to use azodicarbonamide in an unspecified quantity ("under 2 %") in their standard hamburger buns. [18]

Related Research Articles

<span class="mw-page-title-main">Food additive</span> Substances added to food

Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives have been used for centuries as part of an effort to preserve food, for example vinegar (pickling), salt (salting), smoke (smoking), sugar (crystallization), etc. This allows for longer-lasting foods such as bacon, sweets or wines. With the advent of ultra-processed foods in the second half of the twentieth century, many additives have been introduced, of both natural and artificial origin. Food additives also include substances that may be introduced to food indirectly in the manufacturing process, through packaging, or during storage or transport.

<span class="mw-page-title-main">Bread</span> Food made of flour and water

Bread is a staple food prepared from a dough of flour and water, usually by baking. Throughout recorded history and around the world, it has been an important part of many cultures' diet. It is one of the oldest human-made foods, having been of significance since the dawn of agriculture, and plays an essential role in both religious rituals and secular culture.

<span class="mw-page-title-main">Polyurethane</span> Polymer composed of a chain of organic units joined by carbamate (urethane) links

Polyurethane refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from a wide range of starting materials. This chemical variety produces polyurethanes with different chemical structures leading to many different applications. These include rigid and flexible foams, and coatings, adhesives, electrical potting compounds, and fibers such as spandex and polyurethane laminate (PUL). Foams are the largest application accounting for 67% of all polyurethane produced in 2016.

<span class="mw-page-title-main">Isocyanate</span> Chemical group (–N=C=O)

In organic chemistry, isocyanate is the functional group with the formula R−N=C=O. Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyanates are manufactured for the production of polyurethanes, a class of polymers.

<span class="mw-page-title-main">Polystyrene</span> Polymer resin widely used in packaging

Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a poor barrier to air and water vapor and has a relatively low melting point. Polystyrene is one of the most widely used plastics, with the scale of its production being several million tonnes per year. Polystyrene is naturally transparent, but can be colored with colorants. Uses include protective packaging, containers, lids, bottles, trays, tumblers, disposable cutlery, in the making of models, and as an alternative material for phonograph records.

<span class="mw-page-title-main">Nitrogen dioxide</span> Chemical compound with formula NO₂

Nitrogen dioxide is a chemical compound with the formula NO2. One of several nitrogen oxides, nitrogen dioxide is a reddish-brown gas. It is a paramagnetic, bent molecule with C2v point group symmetry. Industrially, NO2 is an intermediate in the synthesis of nitric acid, millions of tons of which are produced each year, primarily for the production of fertilizers.

<span class="mw-page-title-main">Foam</span> Form of matter

Foams are materials formed by trapping pockets of gas in a liquid or solid.

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

Ammonium bicarbonate is an inorganic compound with formula (NH4)HCO3. The compound has many names, reflecting its long history. Chemically speaking, it is the bicarbonate salt of the ammonium ion. It is a colourless solid that degrades readily to carbon dioxide, water and ammonia.

<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.

<span class="mw-page-title-main">Ethylene-vinyl acetate</span> Chemical compound

Ethylene-vinyl acetate (EVA), also known as poly(ethylene-vinyl acetate) (PEVA), is a copolymer of ethylene and vinyl acetate. The weight percent of vinyl acetate usually varies from 10 to 50%, with the remainder being ethylene. There are three different types of EVA copolymer, which differ in the vinyl acetate (VA) content and the way the materials are used.

<span class="mw-page-title-main">Cyanuric acid</span> Chemical compound belonging to the class of triazine

Cyanuric acid or 1,3,5-triazine-2,4,6-triol is a chemical compound with the formula (CNOH)3. Like many industrially useful chemicals, this triazine has many synonyms. This white, odorless solid finds use as a precursor or a component of bleaches, disinfectants, and herbicides. In 1997, worldwide production was 160 000 tonnes.

<span class="mw-page-title-main">Methylene diphenyl diisocyanate</span> Aromatic diisocyanate

Methylene diphenyl diisocyanate (MDI) is an aromatic diisocyanate. Three isomers are common, varying by the positions of the isocyanate groups around the rings: 2,2′-MDI, 2,4′-MDI, and 4,4′-MDI. The 4,4′ isomer is most widely used, and is also known as 4,4′-diphenylmethane diisocyanate. This isomer is also known as Pure MDI. MDI reacts with polyols in the manufacture of polyurethane. It is the most produced diisocyanate, accounting for 61.3% of the global market in the year 2000.

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

Sulfamic acid, also known as amidosulfonic acid, amidosulfuric acid, aminosulfonic acid, sulphamic acid and sulfamidic acid, is a molecular compound with the formula H3NSO3. This colourless, water-soluble compound finds many applications. Sulfamic acid melts at 205 °C before decomposing at higher temperatures to water, sulfur trioxide, sulfur dioxide and nitrogen.

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

Potassium bromate is a bromate of potassium and takes the form of white crystals or powder. It is a strong oxidizing agent.

Flour bleaching agent is the agent added to fresh milled grains to whiten the flour by removing the yellow colour pigment called xanthophyll. It whitens the flour, which is used in the baking industry.

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

Semicarbazide is the chemical compound with the formula OC(NH2)(N2H3). It is a water-soluble white solid. It is a derivative of urea.

Diimide, also called diazene or diimine, is a compound having the formula HN=NH. It exists as two geometric isomers, E (trans) and Z (cis). The term diazene is more common for organic derivatives of diimide. Thus, azobenzene is an example of an organic diazene.

Occupational asthma is new onset asthma or the recurrence of previously quiescent asthma directly caused by exposure to an agent at workplace. It is an occupational lung disease and a type of work-related asthma. Agents that can induce occupational asthma can be grouped into sensitizers and irritants.

<span class="mw-page-title-main">Dough conditioner</span>

A dough conditioner, flour treatment agent, improving agent or bread improver is any ingredient or chemical added to bread dough to strengthen its texture or otherwise improve it in some way. Dough conditioners may include enzymes, yeast nutrients, mineral salts, oxidants and reductants, bleaching agents and emulsifiers. They are food additives combined with flour to improve baking functionality. Flour treatment agents are used to increase the speed of dough rising and to improve the strength and workability of the dough.

Transamidation is a chemical reaction in which an amide reacts with an amine to generate a new amide:

References

  1. ↑ "Azodicarbonamide (CICADS)". Inchem. International Programme on Chemical Safety. Archived from the original on 24 August 2010. Retrieved 14 August 2010. Also published by World Health Organization, Geneva, 1999.
  2. ↑ Arts, Josje; Kimber, Ian (October 2017). "Azodicarbonamide (ADCA): A reconsideration of classification as a respiratory sensitiser". Regulatory Toxicology and Pharmacology. 89: 268–278. doi: 10.1016/j.yrtph.2017.07.018 . PMID   28734852.
  3. ↑ "Almost 500 Foods Contain the 'Yoga Mat' Compound. Should We Care?". NPR .
  4. ↑ Bryden, J. H. (10 January 1961). "The crystal structure of azodicarbonamide". Acta Crystallographica. 14 (1): 61–63. doi:10.1107/S0365110X61000139.
  5. 1 2 Heinz Weber; Isidoor De Grave; Eckhard Röhrl; Volker Altstädt (2016). "Foamed Plastics". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. pp. 1–54. doi:10.1002/14356007.a11_435.pub2. ISBN   978-3-527-30673-2.
  6. ↑ Friend, John (2009). History of Yoga Mat - Looking back with Friends.
  7. 1 2 3 FDA Frequently Asked Questions on Azodicarbonamide (ADA) Page Last Updated: 20 June 2014
  8. 1 2 WHO FAO 1965. Toxicological Evaluation of Some Antimicrobials, Antioxidants, Emulsifiers, Stabilizers, Flour-Treatment Agents, Acids and Bases: Azodicarbonamide FAO Nutrition Meetings Report Series No. 40A,B,C. WHO/Food Add./67.29
  9. 1 2 "The Yoga-Mat Chemical's Quiet Fast-Food Exit". Bloomberg . Retrieved 8 August 2016.
  10. ↑ "Concise International Chemical Assessment Document 16: Azodicarbonamide" (PDF). World Health Organization . Retrieved 5 February 2014.
  11. ↑ "Substances causing/worsening asthma". UK Occupational Health and Safety. WorkSafe Victoria. Archived from the original on 31 May 2013. Retrieved 14 August 2010.
  12. ↑ "Candidate List of substances of very high concern for Authorisation". ECHA. Retrieved 30 October 2018. Diazene-1,2-dicarboxamide (C,C'-azodi(formamide)) (ADCA)... respiratory sensitising properties (Article 57(f) - human health)
  13. 1 2 Smith, Jim; Hong-Shum, Lily (2011). Food additives data book (2nd ed.). Chichester, West Sussex: Wiley-Blackwell. p. 548. ISBN   978-1-4051-9543-0.
  14. ↑ European Commission. "European Union: Authorisation of Additives". Archived from the original on 31 December 2014. Retrieved 31 December 2014.
  15. 1 2 "COMMISSION DIRECTIVE 2004/1/EC of 6 January 2004 amending Directive 2002/72/EC as regards the suspension of the use of azodicarbonamide as blowing agent". Official Journal of the European Union. 13 January 2004. Retrieved 10 March 2011.
  16. ↑ "21CFR172.806". Code of Federal Regulations . 1 April 2012.
  17. 1 2 Landau, Elizabeth (17 February 2014). "Subway to remove 'dough conditioner' chemical from bread". CNN. Retrieved 3 November 2015.
  18. ↑ All American Foodawrestaurants.com Archived 22 April 2022 at the Wayback Machine
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.