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{{chembox |
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{{chembox |
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| verifiedrevid = 444010620 |
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| Watchedfields = changed |
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| Name = '''Methanethiol''' |
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| verifiedrevid = 444011638 |
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| ImageFile_Ref = {{chemboximage|correct|??}} |
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| ImageFile = Methanethiol-2D.png |
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| Name = Methanethiol |
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| ImageFile_Ref = {{chemboximage|correct|??}} |
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| ImageSize = 150px |
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| ImageName = Methanethiol |
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| ImageFile = Methanethiol.svg |
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| ImageSize = 150px |
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| ImageFileL1 = Methanethiol-3D-balls.png |
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| ImageName = Methanethiol |
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| ImageSizeL1 = 120px |
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| ImageFileL1 = Methanethiol-3D-balls.png |
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| ImageNameL1 = Ball-and-stick model of the methanethiol molecule |
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| ImageNameL1 = Ball-and-stick model of the methanethiol molecule |
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| ImageFileR1 = Methanethiol-3D-vdW.png |
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| ImageFileR1 = Methanethiol-3D-vdW.png |
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| ImageSizeR1 = 120px |
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| ImageNameR1 = Space-filling model of the methanethiol molecule |
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| ImageNameR1 = Space-filling model of the methanethiol molecule |
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| IUPACName = Methanethiol |
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| PIN = Methanethiol |
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| OtherNames = methyl mercaptan<br />mercaptomethane<br />thiomethyl alcohol |
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| OtherNames = Methyl mercaptan<br />Mercaptomethane<br />Methiol<br />Thiomethyl alcohol/Thiomethanol<br />Methylthiol |
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| Section1 = {{Chembox Identifiers |
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|Section1={{Chembox Identifiers |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspiders}} |
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| ChemSpiderID = 855 |
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| ChemSpiderID = 855 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| KEGG_Ref = {{keggcite|correct|kegg}} |
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| KEGG_Ref = {{keggcite|correct|kegg}} |
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| KEGG = C00409 |
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| KEGG = C00409 |
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| PubChem = 878 |
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| InChI = 1/CH4S/c1-2/h2H,1H3 |
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| InChI = 1/CH3SH/c1-2/h2H,1H3 |
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| InChIKey = LSDPWZHWYPCBBB-UHFFFAOYAW |
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| InChIKey = LSDPWZHWYPCBBB-UHFFFAOYAW |
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| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChI_Ref = {{stdinchicite|changed|chemspider}} |
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| StdInChI = 1S/CH4S/c1-2/h2H,1H3 |
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| StdInChI = 1S/CH3SH/c1-2/h2H,1H3 |
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChIKey = LSDPWZHWYPCBBB-UHFFFAOYSA-N |
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| StdInChIKey = LSDPWZHWYPCBBB-UHFFFAOYSA-N |
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| CASNo = 74-93-1 |
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| CASNo = 74-93-1 |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| ChEBI_Ref = {{ebicite|correct|EBI}} |
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| ChEBI_Ref = {{ebicite|correct|EBI}} |
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| ChEBI = 16007 |
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| ChEBI = 16007 |
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| DTXSID = DTXSID5026382 |
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| RTECS = PB4375000 |
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| UNNumber = 1064 |
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| EINECS = 200-822-1 |
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| 3DMet = B00105 |
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| SMILES = SC |
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| SMILES = SC |
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}} |
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}} |
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| Section2 = {{Chembox Properties |
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|Section2={{Chembox Properties |
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| Formula = CH<sub>4</sub>S |
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| Formula = CH<sub>3</sub>SH |
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| MolarMass = 48.11 g·mol<sup>−1</sup> |
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| MolarMass = 48.11 g·mol<sup>−1</sup> |
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| Appearance = colorless gas<ref name=PGCH/> |
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| MeltingPtC = -123 |
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| Odor = Distinctive, like that of rotten cabbage or eggs |
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| BoilingPtC = 5.95 |
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| pKa = ~10.4 |
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| MeltingPtC = -123 |
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| BoilingPtC = 5.95 |
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| Solubility = 2% |
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| Solvent = |
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| SolubleOther = alcohol, ether |
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| pKa = ~10.4 |
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| VaporPressure = 1.7 atm (20°C)<ref name=PGCH/> |
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| Density = 0.9 g/mL (liquid at 0°C)<ref name=PGCH/> |
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}} |
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|Section3={{Chembox Hazards |
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| GHSPictograms = {{GHS02}}{{GHS06}}{{GHS08}}{{GHS09}} |
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| GHSSignalWord = Danger |
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| HPhrases = {{H-phrases|220|331|410}} |
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| PPhrases = {{P-phrases|210|261|271|273|304+340|311|321|377|381|391|403|403+233|405|501}} |
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| NFPA-H = 4 |
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| NFPA-F = 4 |
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| NFPA-R = 1 |
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| IDLH = 150 ppm<ref name=PGCH>{{PGCH|0425}}</ref> |
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| LC50 = 3.3 ppm (mouse, 2 hr)<br/>675 ppm (rat, 4 hr)<ref name=IDLH>{{IDLH|74931|Methyl mercaptan}}</ref> |
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| LD50 = 60.67 mg/kg (mammal)<ref name=IDLH/>| PEL = C 10 ppm (20 mg/m<sup>3</sup>)<ref name=PGCH/> |
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| REL = C 0.5 ppm (1 mg/m<sup>3</sup>) <ref name=PGCH/> |
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| FlashPtF = 0 |
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| FlashPt_ref = <ref name=PGCH/> |
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| AutoignitionPtF = 687 |
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| AutoignitionPt_ref = <ref>{{cite web |title=Sigma Aldrich Methanethiol SDS |url=https://www.sigmaaldrich.com/US/en/sds/aldrich/742805 | website=Sigma Aldrich |publisher=Millipore Sigma |access-date=Nov 1, 2022}}</ref> |
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| ExploLimits = 3.9%-21.8%<ref name=PGCH/> }} |
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|Section4={{Chembox Related |
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| OtherCompounds = ] |
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] |
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'''Methanethiol''' (also known as '''methyl ]''') is a colorless gas with a smell like rotten ]. It is a natural substance found in the ] and ] of humans and other animal as well as plant tissues. It is disposed of through animal ]. It occurs naturally in certain foods, such as some ]s and ]. It is also one of the main chemicals responsible for ] and the smell of ]. The ] for methanethiol is ]]; it is classified as a ]. It is sometimes abbreviated as '''MeSH'''. |
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'''Methanethiol''' {{IPAc-en|ˌ|m|ɛ|θ|.|eɪ|n|.|ˈ|θ|aɪ|.|ɒ|l}} (also known as '''methyl ]''') is an ] with the ] {{Chem|CH|3|SH}}. It is a colorless gas with a distinctive putrid smell. It is a natural substance found in the ], ] and ] of animals (including humans), as well as in ]. It also occurs naturally in certain foods, such as some ] and ]. It is one of the chemical compounds responsible for ] and the smell of ]. Methanethiol is the simplest ] and is sometimes abbreviated as '''MeSH'''. It is very flammable. |
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==Structure and reactions== |
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The molecule is tetrahedral at the carbon atom, like ]. It is a ], with a ] of ~10.4, but is about a hundred thousand times more acidic than methanol. The colorless salt can be obtained in this way: |
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:CH<sub>3</sub>SH + ] → ] + CH<sub>3</sub>OH |
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The resulting thiolate anion is a strong ]. |
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It can be oxidized to ]: |
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:2CH<sub>3</sub>SH + → CH<sub>3</sub>SSCH<sub>3</sub> + H<sub>2</sub>O |
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Further oxidation takes the ] to two molecules of ], which is odorless. ] deodorizes methanethiol in this way. |
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==Occurrence== |
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==Occurrence== |
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Methanethiol (MeSH) is released as a by-product of ] in ]s. In kraft pulping, ] is ] by nucleophilic attack with the strongly nucleophilic hydrosulfide ion (HS<sup>−</sup>) in a highly alkaline medium. However, in a side reaction, HS<sup>−</sup> attacks methoxyl groups (OMe) in ], demethylating them to give free ] groups (PhO<sup>−</sup>) and releasing MeSH. Due to alkalinity, MeSH is readily deprotonated (]), and the formed MeS<sup>−</sup> ion is also a strong nucleophile, reacting further to ]. The compounds remain in the liquor and are burned in the ], where the sulfur is recovered as ].<ref>Sixta, H.; Potthast, A.; Krotschek, A. W., Chemical Pulping Processes. In Handbook of Pulp, Sixta, H., Ed. Wiley-VCH Verlag GmbH & Co.: Weinheim, 2006; Vol. 1, p 169 (109–510).</ref> |
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Methanethiol is released from decaying organic matter in ]es and is present in the ] of certain regions, in ], and in some ]s. |
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Methanethiol is released from decaying organic matter in ]es and is present in the ] of certain regions, in ], and in some ]s. It occurs in various plants and vegetables, such as radishes. |
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In surface seawater, methanethiol is the primary breakdown product of the algal metabolite ] (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 ] (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 ] in some anaerobic soils. |
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In surface ], methanethiol is the primary breakdown product of the ] ] ] (DMSP). ] appear to obtain most of the sulfur in their proteins 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).<ref>Charel Wohl, Julián Villamayor and Martí Galí et al. ,Marine emissions of methanethiol increase aerosol cooling in the Southern Ocean.Sci. Adv.10,eadq2465(2024).DOI:10.1126/sciadv.adq2465</ref> Bacteria in environments both with and without oxygen can also convert methanethiol to ] (DMS), although most DMS in surface seawater is produced by a separate pathway.<ref>Kiene, R.P., and Service, S. ," Marine Ecology Progress Series. September, 1991</ref> Both DMS and methanethiol can be used by certain microbes as substrates for ] in some anaerobic soils. |
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Methanethiol is a weak ], with a ] of ~10.4. This acidic property makes it reactive with dissolved ] in aqueous solutions. The ] of these interactions in ] or fresh water environments such as ] has yet to be fully investigated. |
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Methanethiol is a byproduct of the metabolism of ].<ref>Richer, Decker, Belin, Imbs, Montastruc, Giudicelli: , ''British Journal of Clinical Pharmacology'', May 1989</ref> The production of methanethiol in ] after eating asparagus was once thought to be a ]. More recent research suggests that the peculiar odor is in fact produced by all humans after consuming asparagus, while the ability to detect it (methanethiol being one of many components in "asparagus pee") is in fact the genetic trait.<ref>{{cite journal |journal=Br Med J |volume=281 |pages=1676–8 |year= 1980 |vauthors=Lison M, Blondheim SH, Melmed RN |title=A polymorphism of the ability to smell urinary metabolites of asparagus |pmid=7448566 |doi= 10.1136/bmj.281.6256.1676 |issue=6256 |pmc=1715705}}</ref> The chemical components responsible for the change in the odor of urine show as soon as 15 minutes after eating asparagus.<ref> {{webarchive|url=https://web.archive.org/web/20080229081018/http://www.discovery.com/area/skinnyon/skinnyon970115/skinny1.html |date=2008-02-29 }}</ref> |
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The United States ] (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 0.002 ] has been reported. The United States ] Ceiling Limit is listed as 10 ppm. |
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==Preparation== |
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Methanethiol is prepared commercially by the reaction of ] with ] gas over an ] catalyst:<ref name="John Wiley & Sons, Inc">{{cite book |last1=Norell |first1=John |last2=Louthan |first2=Rector P. |title=Kirk-Othmer Concise Encyclopedia of Chemical Technology |edition=3rd |year=1988 |publisher= John Wiley & Sons, Inc.|location=New York|isbn=978-0471801047|pages=946–963 |chapter=Thiols}}</ref> |
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:CH<sub>3</sub>OH + H<sub>2</sub>S → CH<sub>3</sub>SH + H<sub>2</sub>O |
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Although impractical, it can be prepared by the reaction of ] with ].<ref Name="Reid">{{cite book |last1= Reid|first1= E. Emmet |title= Organic Chemistry of Bivalent Sulfur |volume= 1|year=1958 |publisher=Chemical Publishing Company, Inc. |location= New York |pages=32–33, 38}}</ref> |
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==Uses== |
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==Uses== |
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Methanethiol is mainly used to produce ], which is used as a dietary component in poultry and animal feed. Methanethiol is also used in the ]s industry and as a precursor in the manufacture of ]s. It is also released as a decay product of ] in ]s. Due to the extremely low ] of ]s in general, they may be added to otherwise odorless gases such as ], enabling people to detect leaks by smell. And it is Also used by the Underground Mining industry, for injection into fresh-air intakes of the mine to warn miners of emergency situations that require evacuation. |
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Methanethiol is mainly used to produce the essential amino acid ], which is used as a dietary component in poultry and animal feed.<ref name="John Wiley & Sons, Inc"/> Methanethiol is also used in the ] as a moderator for ]<ref name="John Wiley & Sons, Inc" /> and as a precursor in the manufacture of ]s. |
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This chemical is also used in the ] industry as an ], as it mixes well with ]. The characteristic rotting vegetation smell of the mix is widely known by natural gas customers as an indicator of a possible ], even a very minor one.<ref></ref> |
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==Incidents== |
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===St. Petersburg incident=== |
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{{main| December 2005 Saint Petersburg gas incident}} |
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On December 26, 2005, dozens of people at a ] Maksidom home supplies store became ill when gas suspected to be methanethiol was released.<ref>{{cite news |url=http://www.foxnews.com/story/0,2933,179741,00.html |title=Gas Sickens 78 in Russia |publisher=FOXNews.com |date=2005-12-26 |accessdate=2007-02-22}}</ref> The store had received letters threatening to disrupt business during the ]. Three other stores belonging to the same chain found boxes with glass containers and timers that also might have been rigged to release the gas. |
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==Safety== |
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===Milan incident=== |
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The ] (SDS) 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 ] has been reported.<ref name= "Devos">{{cite book|last=Devos|first=M|title=Standardized Human Olfactory Thresholds|year=1990|publisher=IRL Press |location=Oxford |isbn=0199631468 |page=101|author2=F. Patte |author3=J. Rouault |author4=P. Lafort |author5=L. J. Van Gemert}}</ref> The United States ] Ceiling Limit is listed as 10 ppm. |
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In 2004, an exhausted methanethiol canister used by a ] distributor was being returned to a supplier for refilling. The canister sprang a leak while in transit at a road deliveries company in ], a town just north of ], ]. Gas was carried by winds across the eastern half of the city of Milan, causing residents as far as 12 kilometers from the canister to make thousands of calls that overwhelmed emergency services for four hours, and risked hiding actual gas leaks. |
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===San Francisco Bay Area Incident=== |
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=== Accidents === |
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In 2001 a rail car fire of {{Convert|25000|gal|L}} near ] left three people dead and nine injured.<ref>{{Cite web |title=Deadly Explosion At Chemical Plant |url=https://www.cbsnews.com/news/deadly-explosion-at-chemical-plant/ |access-date=2022-05-25 |website=www.cbsnews.com |date=14 July 2001 |language=en-US}}</ref> |
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On November 12, 2009, an out-of-state natural gas supplier injected too much methanethiol into the local supply lines. The resulting odor alarmed many thousands of customers, who called emergency services to report what they thought were leaks. |
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On November 15, 2014, at ]'s ] facility, 24,000 pounds of methyl mercaptan was released and travelled downwind into surrounding areas, killing four and injuring one other.<ref>{{Cite web |title=DuPont La Porte Facility Toxic Chemical Release {{!}} CSB |url=https://www.csb.gov/dupont-la-porte-facility-toxic-chemical-release-/#:~:text=Accident%20Description&text=The%20accident%20at%20DuPont%27s%20facility,fungicide%20manufacturing%20process,%20was%20released. |access-date=2022-06-02 |website=www.csb.gov}}</ref><ref name="CSB Video">{{cite web |author1=US Chemical Safety Board |title=Animation of Chemical Release at DuPont's La Porte Facility |url=https://www.youtube.com/watch?v=pbFzuS8Bdhw&pp=ygUQbWV0aHlsIG1lcmNhcHRhbg%3D%3D |website=Youtube |access-date=8 October 2023 |format=Video |date=30 September 2015}}</ref> In 2023, DuPont pleaded guilty to criminal negligence for its role in the leak. The company was ordered to pay a $12 million fine and donate an additional $4 million to the ].<ref>{{Cite web |date=2023-04-24 |title=Southern District of Texas {{!}} DuPont and former employee sentenced for gas release that killed four {{!}} United States Department of Justice |url=https://www.justice.gov/usao-sdtx/pr/dupont-and-former-employee-sentenced-gas-release-killed-four |access-date=2023-11-13 |website=www.justice.gov |language=en}}</ref><ref>{{Cite web |date=2023-04-24 |title=DuPont ordered to pay $16M in Texas plant leak that killed 4 |url=https://fox5sandiego.com/news/business/ap-business/dupont-ordered-to-pay-16m-in-texas-plant-leak-that-killed-4/ |access-date=2023-04-24 |website=FOX 5 San Diego |language=en-US}}</ref> |
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==Asparagus== |
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Methanethiol is a byproduct produced by the metabolism of ].<ref>Richer, Decker, Belin, Imbs, Montastruc, Giudicelli: , ''British Journal of Clinical Pharmacology'', May 1989</ref> The ability to produce methanethiol in urine after eating asparagus was once thought to be a genetic trait. However recent research suggests that the peculiar odor is in fact produced by all humans after consuming asparagus, while the ability to detect it (methanethiol being one of many components in "asparagus pee") is in fact the genetic trait.<ref>{{cite journal | journal=Br Med J | volume=281 | page=1676 | year= 1980 | author=Lison M, Blondheim SH, Melmed RN. | title=A polymorphism of the ability to smell urinary metabolites of asparagus | pmid=7448566 | doi =10.1136/bmj.281.6256.1676 | issue=6256 | pmc=1715705 }}</ref> The chemical components responsible for the change in the odor of urine show as soon as 15 minutes after eating asparagus.<ref></ref> |
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On July 14, 2022, there was an accidental release of methanethiol in ]. While there were no injuries, a rare weather event caused the odor to persist for several hours. Many believed they were experiencing a ], which led to a high volume of emergency calls and the closure of several local government offices.<ref>{{Cite news |last=Limehouse |first=Jonathan |date=2022-07-14 |title=What is the strong natural gas odor smell in Charlotte NC? |work=Charlotte Observer |url=https://www.charlotteobserver.com/news/local/article263462253.html |access-date=2022-07-14 |archive-url=https://web.archive.org/web/20220715063619/https://www.charlotteobserver.com/news/local/article263462253.html |archive-date=2022-07-15}}</ref> |
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==See also== |
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*] |
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On April 10, 2024, an accidental release<ref>{{cite web |last1=Carr |first1=Dillon |title=Mansfield-area schools back to normal following natural gas scare |url=https://www.richlandsource.com/2024/04/10/area-schools-back-to-normal-following-natural-gas-scare/ |website=Richland Source |date=10 April 2024 |access-date=2024-04-11}}</ref> of a higher-than expected level of methyl mercaptan into the natural gas supply was attributed to an "upstream supplier" for ]. This release was noticed by residents in at least ], ], and ] counties in Ohio. Numerous schools cancelled their school day and numerous evacuations took place out of an abundance of caution prior to the understanding of the source of the odor. No known injuries or deaths were reported. |
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==References== |
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{{Reflist|2}} |
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==External links== |
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==External links== |
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{{Molecules detected in outer space}} |
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{{Authority control}} |
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==References== |
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{{reflist}} |
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