Aaron: slightly enhance information per sources

2026-03-19T21:36:15Z

slightly enhance information per sources

->Linguist111: Reverted 1 edit by 195.224.74.136 (talk) to last revision by Zakblade2000

2022-01-06T14:23:18Z

Reverted 1 edit by 195.224.74.136 (talk) to last revision by Zakblade2000

New page

{{Use dmy dates|date=July 2018}}
{{distinguish|Methyl isocyanide}}
{{Chembox
| Watchedfields = changed
| verifiedrevid = 451299397
| ImageFile = Methyl isocyanate.svg
| ImageSize =
| ImageName = Methyl isocyanate
| ImageFile1 = Methyl-isocyanate-3D-vdW.png
| ImageSize1 =
| ImageName1 = Methyl isocyanate
| PIN = Isocyanatomethane 
| OtherNames = Methyl carbylamine MIC
|Section1={{Chembox Identifiers
| IUPHAR_ligand = 6290
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 624-83-9
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = C588JJ4BV9
| PubChem = 12228
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 11727
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 59059
| SMILES = O=C=NC
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI =1S/C2H3NO/c1-3-2-4/h1H3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = HAMGRBXTJNITHG-UHFFFAOYSA-N
}}
|Section2={{Chembox Properties
| Formula =C2H3NO
| MolarMass = 57.051 g/mol
| Appearance = Colorless liquid
| Odor = Sharp, pungent odor<ref name=PGCH/>
| Density = 0.9230 g/cm3 at 27 °C
| MeltingPtC = −45
| MeltingPt_notes = <ref name="hand">{{RubberBible87th}}</ref>
| BoilingPtC = 38.3
| BoilingPt_notes = <ref name="hand"/>
| Solubility = 10% (15°C)<ref name=PGCH/>
| VaporPressure = 57.7 [[kPa]]
}}
|Section3={{Chembox Structure
| CrystalStruct =
| Coordination =
| MolShape =
| Dipole = 2.8 [[Debye|D]]
}}
|Section4={{Chembox Thermochemistry
| DeltaHf = −92.0 [[kJ/mol|kJ·mol−1]]<ref name="hand"/>
| DeltaHc =
| Entropy =
| HeatCapacity =
}}
|Section8={{Chembox Hazards
| MainHazards =
| GHSPictograms = {{gHS skull and crossbones}} {{gHS health hazard}} {{gHS flame}} {{gHS corrosion}} {{GHS07}}
| HPhrases = {{h-phrases|225|300|311|315|317|318|330|334|335|361d}}
| PPhrases = {{p-phrases|201|202|210|233|240|241|242|243|260|261|264|270|271|272|280|281|284|285|301+310|302+352|303+361+353|304+340|304+341|305+351+338|308+313|310|312|320|321|322|330|332+313|333+313|342+311|361|362|363|370+378|403+233|403+235|405|501}}
| NFPA-H = 4
| NFPA-F = 3
| NFPA-R = 3
| NFPA-S = W
| FlashPtC = −7
| AutoignitionPtC = 534
| ExploLimits = 5.3–26%<ref name="hand"/>
| IDLH = 3 ppm<ref name=PGCH>{{PGCH|0423}}</ref>
| LC50 = 6.1 ppm (rat, 6 hr) 12.2 ppm (mouse, 6 hr) 5.4 ppm (guinea pig, 6 hr) 21 ppm (rat, 2 hr)<ref name=IDLH>{{IDLH|624839|Methyl isocyanate}}</ref>
| LD50 = 120 mg/kg (oral, mouse) 51.5 mg/kg (oral, rat)<ref name=IDLH/>
| REL = TWA 0.02 ppm (0.05 mg/m3) [skin]<ref name=PGCH/>
| PEL = TWA 0.02 ppm (0.05 mg/m3) [skin]<ref name=PGCH/>
}}<ref>{{cite web |url=http://www.nmsu.edu/safety/programs/chem_safety/NFPA-ratingJ-R.htm |title=NFPA Hazard Rating Information for Common Chemicals |publisher=nmsu.edu |access-date=2021-06-10 |url-status=dead |archive-url=https://web.archive.org/web/20150217040510/http://www.nmsu.edu/safety/programs/chem_safety/NFPA-ratingJ-R.htm |archive-date=2015-02-17 }}</ref>
|Section9={{Chembox Related
| OtherCompounds = [[Methyl isothiocyanate]]
}}
}}

'''Methyl isocyanate''' ('''MIC''') is an [[organic compound]] with the molecular formula CH3NCO. Synonyms are isocyanatomethane, methyl carbylamine and MIC. Methyl isocyanate is an intermediate chemical in the production of [[carbamate]] [[pesticide]]s (such as [[carbaryl]], [[carbofuran]], [[methomyl]], and [[aldicarb]]). It has also been used in the production of [[rubber]]s and [[adhesive]]s. As a highly [[toxic]] and irritating material, it is extremely hazardous to human health. It was the principal toxicant involved in the [[Bhopal disaster]], which killed 2,259 people initially and officially 20,000 people in total.<ref>Methyl Isocyanate. Union Carbide F-41443A – 7/76. Union Carbide Corporation, New York 1976</ref><ref>Operating Manual Part II. Methyl Isocyanate Unit. Union Carbide India Limited, Agricultural Products Division, 1979</ref><ref name="irs">{{cite journal | vauthors = Broughton E | title = The Bhopal disaster and its aftermath: a review | journal = Environmental Health | volume = 4 | issue = 1 | pages = 6 | date = May 2005 | pmid = 15882472 | pmc = 1142333 | doi = 10.1186/1476-069X-4-6 }}</ref><ref>{{cite journal |vauthors=Eckerman I |title=Chemical Industry and Public Health — Bhopal as an example |journal=MPH |year=2001 |volume=2001 |issue=24 |publisher=Nordic School of Public Health |location=Göteborg, Sweden |issn=1104-5701 |url=http://www.lakareformiljon.org/images/stories/dokument/2009/bhopal_gas_disaster.pdf |url-status=live |archive-url=https://web.archive.org/web/20121030030142/http://www.lakareformiljon.org/images/stories/dokument/2009/bhopal_gas_disaster.pdf |archive-date=2012-10-30 }}</ref><ref>{{cite book |vauthors=Eckerman I |title=The Bhopal Saga - Causes and Consequences of the World's Largest Industrial Disaster |url=http://www.eckerman.nu/default.cfm?page=The%20Bhopal%20Saga |year=2004 |publisher=Universities Press |location=India |isbn=81-7371-515-7 |url-status=dead |archive-url=https://web.archive.org/web/20070610212157/http://www.eckerman.nu/default.cfm?page=The%20Bhopal%20Saga |archive-date=2007-06-10 }}</ref><ref>{{cite web |url=http://history1900s.about.com/od/1980s/qt/bhopal.htm |vauthors=Rosenberg J |publisher=About.com |title=At 1984 - Huge Poison Gas Leak in Bhopal, India |access-date=2008-07-10 |url-status=live |archive-url=https://web.archive.org/web/20071202051803/http://history1900s.about.com/od/1980s/qt/bhopal.htm |archive-date=2007-12-02 }}</ref><ref name="Eckerman2013">{{cite book |vauthors=Eckerman I |chapter=Bhopal Gas Catastrophe 1984: Causes and Consequences |publisher=Elsevier |title=Reference Module in Earth Systems and Environmental Sciences |pages=272–287 |year=2013 |doi=10.1016/B978-0-12-409548-9.01903-5|isbn=978-0-12-409548-9}}</ref>

== Physical properties ==

Methyl isocyanate is a colorless, poisonous, [[Lachrymatory agent|lachrymatory]] ([[Tears|tearing]] agent), flammable liquid.<ref name="Union Carbide 1967">Union Carbide Corporation "Methyl Isocyanate" Product Information Publication, F-41443, November 1967.</ref> It is soluble in water to 6–10 parts per 100 parts, but it also reacts with water (see [[#Reactions|Reactions]] below).

== Manufacture ==

Methyl isocyanate is usually manufactured by the reaction of [[Methylamine|monomethylamine]] and [[phosgene]]. For large scale production, it is advantageous to combine these reactants at higher temperature in the gas phase. A mixture of methyl isocyanate and two moles of [[hydrogen chloride]] is formed, but N-methylcarbamoyl chloride (MCC) forms as the mixture is condensed, leaving one [[Mole (unit)|mole]] of [[hydrogen chloride]] as a gas.

[[File:MMA plus Phosgene diagram.svg|none]]
The methyl isocyanate is obtained by treating the MCC with a tertiary amine, such as [[dimethylaniline|N,N-dimethylaniline]], or with [[pyridine]]<ref>{{cite patent |country=US |number=2480088 |status=patent |inventor=Slocombe, R. J.; Hardy, E. E. |title=Process of Producing Carbamyl Chlorides |gdate=1949-08-23 |assign1=Monsanto}}</ref> or by separating it by using distillation techniques.<ref>{{cite patent |country=FR |number=1400863 |status=patent |inventor=Merz, W. |title=Procédé et dispositif de préparation d'isocyanates d'alkyle |assign1=Bayer |gdate=1965-05-28}}</ref>

[[File:MCC to MIC & HCl.svg|none]]
Methyl isocyanate is also manufactured from N-methylformamide and air. In the latter process, it is immediately consumed in a closed-loop process to make methomyl.<ref>Chemical Week, ''"A fleeting existence for toxic-gas molecules"'' p. 9, 12 June 1985.</ref> Other manufacturing methods have been reported.<ref>{{cite patent |country=DE |number=2828259 |status=patent |inventor=Giesselmann, G.; Guenther, K.; Fuenten, W. |title=Verfahren zur Herstellung von Methyl Isocyanate |gdate=1980-01-10 |assign1=Degussa}}</ref><ref>{{cite journal |journal=Chemical Week |year=1985 |title=A safer method for making carbamates |page=136 |volume=1985b |issue=20}}</ref>

== Reactions ==

Methyl isocyanate reacts readily with many substances that contain N-H or O-H groups. With water, it forms [[dimethylurea|1,3-dimethylurea]] and [[carbon dioxide]] with the evolution of heat (325 calories per gram of MIC):

[[File:MIC & water to DMU & TMB.png|none]]
At 25 °C, in excess water, half of the MIC is consumed in 9 min.;<ref>{{cite journal |vauthors=Castro EA, Moodie RB, Sansom PJ |title=The kinetics of hydrolysis of methyl and phenyl isocyanates |journal=Journal of the Chemical Society, Perkin Transactions 2 |year=1985 |volume=1985 |issue=5 |pages=737–742 |doi=10.1039/P29850000737}}</ref> if the heat is not efficiently removed from the mixture, the rate of the reaction will increase and rapidly cause the MIC to boil. If MIC is in excess, [[Biuret|1,3,5-trimethylbiuret]] is formed along with [[carbon dioxide]].<ref name="Union Carbide 1967" /> [[Alcohols]] and [[phenols]], which contain an O-H group, react slowly with MIC, but the reaction can be catalyzed by trialkyl[[amine]]s or dialkyltin dicarboxylate. [[Oxime]]s, [[hydroxylamine]]s, and [[enol]]s also react with MIC to form methylcarbamates.<ref name="Union Carbide 1967" /> These reactions produce the products described below ([[#Uses|Uses]]).

[[File:MIC plus 1-naphthol to carbaryl.svg|none]]
[[Ammonia]], primary, and secondary [[amine]]s rapidly react with MIC to form substituted [[urea]]s. Other N-H compounds, such as amides and [[urea]]s, react much more slowly with MIC.<ref>{{cite book |vauthors=March J |title=Advanced Organic Chemistry |edition=3rd |publisher=John Wiley & Sons |location=New York |year=1985 |page=802}}</ref>

It also reacts with itself to form a trimer or higher molecular weight polymers. In the presence of [[catalysts]], MIC reacts with itself to form a solid trimer, trimethyl isocyanurate, or a higher molecular weight polymer:

[[File:MIC to trimer.svg|none]]
[[Alkoxide|Sodium methoxide]], [[Phosphine|triethyl phosphine]], [[ferric chloride]] and certain other metal compounds catalyze the formation of the MIC-trimer, while the high-molecular-weight polymer formation is catalyzed by certain trialkyl[[amine]]s. Since the formation of the MIC trimer is [[exothermic]] (298 calories per gram of MIC), the reaction can lead to violent boiling of the MIC. The high-molecular-weight polymer hydrolyzes in hot water to form the trimethyl isocyanurate. Since catalytic metal salts can be formed from impurities in commercial grade MIC and steel, this product must not be stored in steel drums or tanks.<ref name="Union Carbide 1967" />

== Toxicity ==

Methyl isocyanate is extremely [[toxic]]. There is no known [[antidote]]. The threshold limit value set by the American Conference on Government Industrial Hygienists is 0.02 [[Parts per million|ppm]]. MIC is toxic by inhalation, ingestion and contact in quantities as low as 0.4 [[Parts per million|ppm]]. Exposure symptoms include coughing, [[chest]] pain, [[dyspnea]], [[asthma]], irritation of the [[Human eye|eye]]s, [[human nose|nose]] and [[throat]], as well as [[skin]] damage. Higher levels of exposure, over 21 ppm, can result in pulmonary or lung [[edema]], [[emphysema]] and [[hemorrhage]]s, bronchial [[pneumonia]] and [[death]]. Although the odor of methyl isocyanate cannot be detected at 5 ppm by most people, its potent [[Lachrymatory agent|lachrymal]] properties provide an excellent warning of its presence (at a concentration of 2–4 parts per million (ppm) subject's eyes are irritated, while at 21 ppm, subjects could not tolerate the presence of methyl isocyanate in air).<ref>{{cite journal |vauthors=Kimmerle G, Eben A |title=Zur Toxizität von Methylisocyanat und dessen quantitativer Bestimmung in der Luft |journal=Archiv für Toxikologie |year=1964 |volume=20 |issue=4 |pages=235–241 |doi=10.1007/bf00577897}}</ref>

Proper care must be taken to store methyl isocyanate because of its ease of exothermically polymerizing (see [[#Reactions|Reactions]]) and its similar sensitivity to water. Only stainless steel or glass containers may be safely used; the MIC must be stored at temperatures below {{convert|40|°C}} and preferably at {{convert|4|°C}}.{{fact|date=August 2018}}

The toxic effect of the compound was apparent in the 1984 [[Bhopal disaster]], when around {{convert|42000|kg}} of methyl isocyanate and other gases were released from the underground reservoirs of the [[Union Carbide India Limited]] (UCIL) factory, over a populated area on 3 December 1984, killing about 3,500 people immediately and 15,000 more over the next several years.<ref name="convictions">{{cite news|url=http://news.bbc.co.uk/1/hi/world/south_asia/8725140.stm|title=Bhopal trial: Eight convicted over India gas disaster |date=7 June 2010|work=[[BBC News]]|access-date=7 June 2010| archive-url=https://web.archive.org/web/20100607185745/http://news.bbc.co.uk/1/hi/world/south_asia/8725140.stm| archive-date= 7 June 2010 | url-status=live}}</ref>

=== Mechanism of action ===
Until recent decades, the mechanism of methyl isocyanate toxicity in humans was largely unknown or unclear.<ref>{{cite journal | vauthors = Mehta PS, Mehta AS, Mehta SJ, Makhijani AB | title = Bhopal tragedy's health effects. A review of methyl isocyanate toxicity | journal = JAMA | volume = 264 | issue = 21 | pages = 2781–7 | date = December 1990 | pmid = 2232065 | doi = 10.1001/jama.1990.03450210081037 }}</ref><ref>{{cite journal | vauthors = Varma DR | title = Epidemiological and experimental studies on the effects of methyl isocyanate on the course of pregnancy | journal = Environmental Health Perspectives | volume = 72 | pages = 153–7 | date = June 1987 | pmid = 3622430 | pmc = 1474644 | doi = 10.1289/ehp.8772153 }}</ref> Methyl isocyanate and other isocyanates are electrophiles and are currently thought to cause toxicity by the alkylation of biomolecules.<ref>{{Cite journal|last=Bessac|first=B. F.|last2=Jordt|first2=S.-E.|date=2010-07-01|title=Sensory Detection and Responses to Toxic Gases: Mechanisms, Health Effects, and Countermeasures|journal=Proceedings of the American Thoracic Society|volume=7|issue=4|pages=269–277|doi=10.1513/pats.201001-004sm|pmid=20601631|pmc=3136963|issn=1546-3222}}</ref> The mechanism of methyl isocyanate was previously suspected to be the carbamylation of hemoglobin which would interfere with its oxygen binding capability causing hypoxia. However, experiments showed that when rats and guinea pigs were exposed to methyl isocyanate at concentrations above the LC50, only 2% of hemoglobin molecules were carbamylated, suggesting that this is probably not the mechanism of toxicity.<ref>{{Cite journal|last=Varma|first=Daya R.|last2=Guest|first2=Ian|date=1993|title=The Bhopal accident and methyl isocyanate toxicity|journal=Journal of Toxicology and Environmental Health|language=en|volume=40|issue=4|pages=513–529|doi=10.1080/15287399309531816|pmid=8277516|issn=0098-4108}}</ref><ref>{{Cite journal|last=Ramachandran|first=P.K.|last2=Gandhe|first2=B.R.|last3=Venkateswaran|first3=K.S.|last4=Kaushik|first4=M.P.|last5=Vijayaraghavan|first5=R.|last6=Agarwal|first6=G.S.|last7=Gopalan|first7=N.|last8=Suryanarayana|first8=M.V.S.|last9=Shinde|first9=S.K.|last10=Sriramachari|first10=S.|date=1988|title=Gas chromatographic studies of the carbamylation of haemoglobin by methyl isocyanate in rats and rabbits|journal=Journal of Chromatography B: Biomedical Sciences and Applications|volume=426|issue=2|pages=239–247|doi=10.1016/s0378-4347(00)81952-0|pmid=3392138|issn=0378-4347}}</ref>

== Extraterrestrial occurrence ==
[[File:ALMA detects methyl isocyanate around young Sun-like stars.jpg|thumb|A photo illustration of methyl isocyanate around young Sun-like stars, as detected by the [[Atacama Large Millimeter Array|ALMA]].<ref>{{cite web|title=ALMA Finds Ingredient of Life Around Infant Sun-like Stars|url=https://www.eso.org/public/news/eso1718/|website=www.eso.org|access-date=8 June 2017|url-status=live|archive-url=https://web.archive.org/web/20170608143057/http://www.eso.org/public/news/eso1718/|archive-date=8 June 2017}}</ref>]]

On 30 July 2015, scientists reported that upon the first touchdown of the ''[[Philae (spacecraft)|Philae]]'' lander on [[comet]] [[67/P]]{{'s}} surface, measurements by the COSAC and Ptolemy instruments revealed sixteen [[organic compound]]s, four of which were seen for the first time on a comet, including [[acetamide]], [[acetone]], methyl isocyanate and [[propionaldehyde]].<ref name="wapo20150730">{{cite news |url=https://www.washingtonpost.com/world/philae-probe-finds-evidence-that-comets-can-be-cosmic-labs/2015/07/30/63a2fc0e-36e5-11e5-ab7b-6416d97c73c2_story.html |archive-url=https://web.archive.org/web/20181223235109/https://www.washingtonpost.com/world/philae-probe-finds-evidence-that-comets-can-be-cosmic-labs/2015/07/30/63a2fc0e-36e5-11e5-ab7b-6416d97c73c2_story.html |url-status=dead |archive-date=23 December 2018 |title=Philae probe finds evidence that comets can be cosmic labs |work=The Washington Post |agency=Associated Press |vauthors=Jordans F |date=30 July 2015 |access-date=30 July 2015}}</ref><ref name="esa20150730">{{cite web |url=http://www.esa.int/Our_Activities/Space_Science/Rosetta/Science_on_the_surface_of_a_comet |title=Science on the Surface of a Comet |publisher=European Space Agency |date=30 July 2015 |access-date=30 July 2015 |url-status=live |archive-url=https://web.archive.org/web/20150802005802/http://www.esa.int/Our_Activities/Space_Science/Rosetta/Science_on_the_surface_of_a_comet |archive-date=2 August 2015 }}</ref><ref name="SCI-20150731">{{cite journal | vauthors = Bibring JP, Taylor MG, Alexander C, Auster U, Biele J, Finzi AE, Goesmann F, Klingelhoefer G, Kofman W, Mottola S, Seidensticker KJ, Spohn T, Wright I | display-authors = 6 | title = Philae's first look. Philae's First Days on the Comet. Introduction | journal = Science | volume = 349 | issue = 6247 | pages = 493 | date = July 2015 | pmid = 26228139 | doi = 10.1126/science.aac5116 | bibcode = 2015Sci...349..493B | doi-access = free }}</ref>

== References ==
{{Reflist}}

== External links ==
* [https://www.cdc.gov/niosh/topics/isocyanates/ NIOSH Safety and Health Topic: Isocyanates], from the website of the National Institute for Occupational Safety and Health (NIOSH).
* [http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@na+@rel+Methyl+isocyanate U.S. National Library of Medicine: Hazardous Substances Databank – Methyl isocyanate]

{{Chemical agents}}
{{Authority control}}

[[Category:Isocyanates]]
[[Category:Monomers]]
[[Category:Bhopal disaster]]
[[Category:Pulmonary agents]]
[[Category:Lachrymatory agents]]

Methyl isocyanate - Revision history

Aaron: slightly enhance information per sources

->Linguist111: Reverted 1 edit by 195.224.74.136 (talk) to last revision by Zakblade2000