Methanthiol Chemische Eigenschaften,Einsatz,Produktion Methoden
ERSCHEINUNGSBILD
FARBLOSES GAS MIT CHARAKTERISTISCHEM GERUCH.
PHYSIKALISCHE GEFAHREN
Das Gas ist schwerer als Luft und kann sich am Boden ausbreiten. Fernzündung möglich.
CHEMISCHE GEFAHREN
Zersetzung beim Verbrennen unter Bildung giftiger Rauche mit Schwefeloxiden und Schwefelwasserstoff. Reagiert sehr heftig mit starken Oxidationsmitteln. Reagiert mit Wasser, Wasserdampf oder Säurenunter Bildung von entzündlichem und giftigem Gas.
ARBEITSPLATZGRENZWERTE
TLV: 0.5 ppm (als TWA); (ACGIH 2005).
MAK: 0.5 ppm, 1.0 mg/m? Spitzenbegrenzung: überschreitungsfaktor II(2); Schwangerschaft: Gruppe D (DFG 2006).
AUFNAHMEWEGE
Aufnahme in den Körper durch Inhalation.
INHALATIONSGEFAHREN
Eine gesundheitsschädliche Konzentration des Gases in der Luft wird beim Entweichen aus dem Behälter sehr schnell erreicht.
WIRKUNGEN BEI KURZZEITEXPOSITION
WIRKUNGEN BEI KURZZEITEXPOSITION: Die Substanz reizt die Augen und die Atemwege. Möglich sind Auswirkungen auf das Zentralnervensystem mit nachfolgender Atemdepression. Exposition in hohen Konzentrationen kann zu Bewusstlosigkeit führen. Exposition in hohen Konzentrationen kann zum Tod führen. Die Auswirkungen treten u.U. verzögert ein. ärztliche Beobachtung notwendig.
LECKAGE
Gefahrenbereich verlassen! Fachmann zu Rate ziehen! Belüftung. NICHT in die Umwelt gelangen lassen. Persönliche Schutzausrüstung: Umgebungsluftunabhängiges Atemschutzgerät.
R-Sätze Betriebsanweisung:
R12:Hochentzündlich.
R23:Giftig beim Einatmen.
R50/53:Sehr giftig für Wasserorganismen, kann in Gewässern längerfristig schädliche Wirkungen haben.
S-Sätze Betriebsanweisung:
S16:Von Zündquellen fernhalten - Nicht rauchen.
S25:Berührung mit den Augen vermeiden.
S60:Dieses Produkt und sein Behälter sind als gefährlicher Abfall zu entsorgen.
S61:Freisetzung in die Umwelt vermeiden. Besondere Anweisungen einholen/Sicherheitsdatenblatt zu Rate ziehen.
Beschreibung
Methanethiol (also known as methyl mercaptan) is a colorless gas with a smell like rotten cabbage. It is a natural substance found in the blood and brain of humans and other animals as well as plant tissues. It is disposed of through animal feces. It occurs naturally in certain foods, such as some nuts and cheese. It is also one of the main chemicals responsible for bad breath and the smell of flatus. The chemical formula for methanethiol is CH
3SH; it is classified as a thiol. It is sometimes abbreviated as MeSH. It is very flammable.
Chemische Eigenschaften
Methyl mercaptan is a colorless gas or white
liquid with a disagreeable odor like garlic or rotten cabbage. Shipped as a liquefied compressed gas. The odor
threshold is 0.002 ppm.
Physikalische Eigenschaften
Colorless gas with a garlic-like or rotten cabbage odor. An experimentally determined odor
threshold concentration of 2.1 ppb
v was reported by Leonardos et al. (1969). A detection odor
threshold concentration of 81 μg/m
3 (41 ppb
v) was determined by Katz and Talbert (1930).
Occurrence
Methanethiol is released from decaying organic matter in marshes and is present in the natural gas of certain regions, in coal tar, and in some crude oils.
In surface seawater, methanethiol is the primary breakdown product of the algal metabolite dimethylsulfoniopropionate (DMSP). Marine bacteria appear to obtain most of their protein sulfur by the breakdown of DMSP and incorporation of methanethiol, despite the fact that methanethiol is present in seawater at much lower concentrations than sulfate (～0.3 nM vs. 28 mM). Bacteria in oxic and anoxic environments can also convert methanethiol to dimethyl sulfide (DMS), although most DMS in surface seawater is produced by a separate pathway. Both DMS and methanethiol can be used by certain microbes as substrates for methanogenesis in some anaerobic soils.
Methanethiol is a weak acid, with a pKa of ～10.4. This acidic property makes it reactive with dissolved metals in aqueous solutions. The environmental chemistry of these interactions in seawater or fresh water environments such as lakes has yet to be fully investigated.
A material safety data sheet (MSDS) lists methanethiol as a colorless, flammable gas with an extremely strong and repulsive smell. At very high concentrations it is highly toxic and affects the central nervous system. Its penetrating odor provides warning at dangerous concentrations. An odor threshold of 1 ppb has been reported. The United States OSHA Ceiling Limit is listed as 10 ppm.
Verwenden
Methanethiol is mainly used to produce methionine, which is used as a dietary component in poultry and animal feed. Methanethiol is also used in the plastics industry and as a precursor in the manufacture of pesticides. It is released as a by-product of wood pulping in pulp mills.
Methanethiol is also used for communication in mining operations . Releasing the substance into the ventilation system is generally the most efficient and reliable means to alert all workers of an emergency , and is referred to as "releasing the pest" ,This substance's strong odor alerts the miners to immediately go to a saferoom.
Since natural gas and propane are colorless and odorless, a small amount of methyl mercaptan or ethyl mercaptan is added to make it easy to detect a gas leak.
synthetische
Methanethiol is prepared commercially by the reaction of methanol with hydrogen sulfide gas over an acidic solid catalyst, such as alumina. It can be prepared by the reaction of methyl iodide with thiourea.
Air & Water Reaktionen
Highly flammable. Reacts with water, steam or acids to produce toxic, flammable vapors [Lewis].
Reaktivität anzeigen
METHYL MERCAPTAN is a reducing agent--can react vigorously with oxidizing agents. Dangerous fire or explosion hazard when exposed to heat, flame, sparks or strong oxidizing agents (e.g., calcium hypochlorite). When heating to decomposition emits highly toxic fumes of oxides of sulfur [Lewis, 3rd ed., 1993, p. 862]. Violent reaction with mercury(II) oxide [Klason P., Ber., 1887, 20, p. 3410].
Hazard
Flammable, dangerous fire risk. Explosive
limits in air 3.9–21.8%. Strong irritant. Liver damage.
Health Hazard
Can cause death by respiratory paralysis. It is an eye and respiratory tract irritant. Exposure results in pulmonary edema and hepatic and renal damage.
Brandgefahr
Combustion produces irritating sulfur dioxide. Flash back along vapor track may occur. Very dangerous when exposed to heat, flame, or oxidizers. On decomposition METHYL MERCAPTAN emits highly toxic fumes of sulfur oxides. METHYL MERCAPTAN will react with water, steam or acids to produce toxic and flammable vapors; and can react vigorously with oxidizing materials. Irritating sulfur dioxide is produced upon combustion. When heated to decomposition, METHYL MERCAPTAN emits highly toxic fumes and flammable vapors. Incompatible with mercuric oxide and oxidizing materials. Avoid direct sunlight, and areas of high fire hazards. Hazardous polymerization may not occur.
Sicherheitsprofil
Poison by inhalation.
Mutation data reported. A common air
contaminant. Very dangerous fire hazard
when exposed to heat or flame; can react
vigorously with oxidzing materials.
Explosive in the form of vapor when
exposed to heat or flame. Reacts with water,
steam, or acids to produce toxic and
flammable vapors. Violent reaction with
mercury(II) oxide. To fight fire, use alcohol
foam, CO2, dry chemical. Upon
decomposition it emits highly toxic fumes of
SOx.
mögliche Exposition
Methyl mercaptan is used in methionine synthesis, and widely as an intermediate in pesticide
manufacture. A foul-smelling odorant usually added to
chemicals, including pesticides.
Environmental Fate
Biological. After 20 d, methyl mercaptan started to degrade in anaerobic sediments and sludges
producing stoichiometric amounts of methane. Complete degradation was achieved after 20 d. Under
anaerobic freshwater conditions, methyl mercaptan were degraded by methanogenic archea (van
Leerdam et al., 2006).
Photolytic. Sunlight irradiation of a methyl mercaptan-nitrogen oxide mixture in an outdoor
chamber yielded formaldehyde, sulfur dioxide, nitric acid, methyl nitrate, methanesulfonic acid,
and an inorganic sulfate (Grosjean, 1984a).
Chemical/Physical. In the presence of nitric oxide, gaseous methyl mercaptan reacted with OH
radicals forming methyl sulfenic acid and methyl thionitrite. The rate constant for this reaction is
2.1 x 10
-11 cm
3/moleculesec at 20 °C (MacLeod et al., 1984).
Forms a crystalline hydrate with water (Patnaik, 1992).
Versand/Shipping
UN1064 Methyl mercaptan, Hazard Class: 2.3;
Labels: 2.3-Poisonous gas, 2.1-Flammable gas, Inhalation
Hazard Zone C. Cylinders must be transported in a secure
upright position, in a well-ventilated truck. Protect cylinder
and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal
law (49CFR) to transport and refill them. It is a violation
of transportation regulations to refill compressed gas cylinders without the express written permission of the owner.
Inkompatibilitäten
Violent reaction with strong oxidizers,
bleaches, copper, nickel and their alloys; aluminum. Reacts
with acids producing flammable and toxic hydrogen
sulfide
Waste disposal
Return refillable compressed
gas cylinders to supplier. Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant
(≥100 kg/mo) must conform to EPA regulations governing
storage, transportation, treatment, and waste disposal.
Incineration followed by effective scrubbing of the effluent
gas.
Methanthiol Upstream-Materialien And Downstream Produkte
Upstream-Materialien
Downstream Produkte
