Methyl isocyanate
- MIC
- Isocyanatomethan
- Isocyansäuremethylester
Colorless, lachrymatory liquid with a pungent odor
Liquid
0.96 g · cm -3
-45 ° C ° C
38 ° C.
46.4 kPa ( 20 ° C)
Decomposes in water and alcohols
1.3637
Risk
0.024 mg · m-3
71 mg · kg -1 ( LD50, rat, oral)
-92.0 KJ / mol
Template: Infobox chemical / molecular formula search available
Methyl isocyanate ( MIC short ) is the simplest ester of isocyanic acid. It is a highly reactive chemical compound which is used for example in the manufacture of insecticides. As the isocyanic acid and the other isocyanates, it is very toxic.
History
In Bhopal, India, located on 3 December 1984, a disastrous chemical accident occurred with methyl isocyanate. It escaped from a faulty tank in a pesticide factory of the American chemical company Union Carbide Corporation near the city between 25 and 40 tonnes of methyl isocyanate. As a result of this chemical accident 3800-25000 people were estimated killed. In addition, there was an immense poisoning the environment.
Production and representation
Technical methyl isocyanate is prepared by the reaction of methyl amine and phosgene. After elimination of hydrogen chloride (HCl) to the intermediate N - Methylcarbamoylchlorid is converted to methyl isocyanate:
Methylamine reacts in the first step at -20 ° C to 60 ° C with elimination of HCl to phosgene N Methylcarbamoylchlorid. In the second step at 100-200 ° C arises with renewed elimination of HCl methyl isocyanate.
Properties
Methyl isocyanate is a volatile, colorless liquid that is highly tear- exciting and focused has a pungent odor. It is highly flammable (flash point at -7 ° C). At slightly elevated temperatures (38 ° C), it proceeds in the gaseous state in which it is heavier than air and with this easily forms explosive mixtures (explosion limits: 5.3 to 26 percent by volume of methyl isocyanate ). Gaseous methyl isocyanate ignites automatically at 535 ° C.
Use
Methyl isocyanate is used mainly for the production of carbamates by reaction with an alcohol ( 1) or for the production of special ureas by reaction with amines (2):
In the pesticide plant of the American chemical company Union Carbide Corporation near the city of Bhopal at the time the active ingredients carbaryl and aldicarb were produced (2- methyl-2 -(methylthio ) propionaldehyde -O- methylcarbamoyloxim ).
By January 2011, these substances were also produced in the Bayer Group's plant in Institute (USA). On 11 January 2011 Bayer announced in this work, which was considered a " sister plant " from Bhopal to end the MIC production until summer 2012. A court in Charleston in the U.S. state of West Virginia has given on 10 February 2011 a lawsuit filed by 16 residents of the Bayer plant in Institute, provisional, and prohibits the production of the highly toxic chemical. Since the action " great prospect of success " have, the competent Judge Joseph Goodwin chose to prohibit a re - starting the system, initially for 14 days. In a hearing on February 25, which concerns the applicant intends to discuss them in detail.
Physiology
The direct toxicity of methyl isocyanate resulted from the ability to attack a number of nucleophilic groups of metabolically active biomolecules. The mechanism for the transport was discovered in 1992. Accordingly, glutathione, a tripeptide, whose job it is actually to protect the organism from damage by toxic substances, methyl isocyanate add reversibly to the thiol group and use it to transport the body.
Safety
Methyl isocyanate caused by exposure irritates the mucous membranes, eyes and lungs, but in victims of severe burns Bhopalunglücks also internal organs were often found. This finding was surprising as methyl isocyanate is reactive to still get into the circulation.
Methyl isocyanate is potentially teratogenic.