Methanethiol

Structural formula
General
Surname	Methanethiol
other names	Methyl mercaptan; Methyl sulfhydrate; Thiomethanol; Methyl hydrosulfide; Methanethioalcohol; Mercaptomethane;
Molecular formula	CH 4 S
Brief description	colorless gas with a putrid, pungent odor
External identifiers / databases
EC number	200-822-1
ECHA InfoCard	100,000,748
PubChem	878
Wikidata	Q409309
properties
Molar mass	48.11 g mol −1
Physical state	gaseous
density	0.8665 g cm −3 (20 ° C)
Melting point	−123 ° C
boiling point	6 ° C
Vapor pressure	170 k Pa (20 ° C)
solubility	poor in water (23.3 g l −1 at 20 ° C)
safety instructions
H and P phrases	H: 220-280-331-410
	P: 210-261-273-304 + 340-311-403 + 233
MAK	DFG / Switzerland: 0.5 ml m −3 or 1 mg m −3
Thermodynamic properties
ΔH f 0	−22.9 kJ / mol
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Methanethiol is a colorless gas with an unpleasant smell of rotten vegetables.

synthesis

Methanethiol is obtained by heating methyl halides with sodium hydrogen sulfide and hydrogen sulfide in ethanol : ${\ displaystyle {\ ce {CH3Br + NaSH -> CH3SH + NaBr}}}$

The technical production takes place by converting methanol and hydrogen sulfide at approx. 400 ° C on tungsten-activated aluminum oxide contact. Alternatively, methanethiol can be produced by reacting carbon disulfide (CS ₂ / H ₂ ) and carbon monoxide with H ₂ / H ₂ S.

Occurrence

Methanethiol occurs naturally in nuts and cheese, but also in the blood, brain and other organs in humans and animals. It arises from the bacterial breakdown of proteins . One cause of the unpleasant halitosis in humans is - along with other volatile sulfur-containing compounds - methanethiol.

Methanethiol is a major decomposition product of dimethyl sulfoniopropionate (DMSP), which is found in bacteria in seawater. It is therefore detectable in water close to the surface. Methanethiol can be converted into dimethyl sulfide by bacteria .

physiology

Larger amounts of methanethiol, such as those produced when an excess of the amino acid L - methionine is broken down, are partially oxidized to carbon dioxide and sulfates in the microsomes of the liver . The latter is detectable in urine and lowers its pH value.

properties

Chemically, methanethiol belongs to the group of alkanethiols and is a weak acid . Their critical temperature is 196.8 ° C, the critical pressure 72.4 bar, the critical density 0.332 kg / l and the triple point temperature at −123.0 ° C (melting temperature).

use

Due to its unpleasant and persistent odor, methanethiol is added to natural gas and propane gas as a warning substance to draw attention to leaks ( odorization ). The perception threshold for humans is around 2 mg / t (0.002 ppm ).

Also, the plant protection products using methanethiol acephate , alanycarb , aldicarb , aldoxycarb , ametryn , Butocarboxim , desmetryn , dimethametryn , dithiopyr , methomyl , Methoprotryn , oxamyl , prometryn , simetryn , terbutryn , thiodicarb and thiofanox shown. The amino acid DL - methionine used as a feed additive is produced on a large industrial scale from methanethiol.

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Entry on methanethiol in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
↑ Entry on methanethiol in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
↑ Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for 74-93-1 or methanethiol ), accessed on November 2, 2015.
↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-20.
↑ Hans Beyer, Wolfgang Walter: Textbook of organic chemistry . 18th edition. S. Hirzel Verlag, Stuttgart 1978, ISBN 3-7776-0342-2 , p. 135 .
↑ Entry on methanethiol. In: Römpp Online . Georg Thieme Verlag, accessed on July 7, 2019.
↑ Wolfgang Legrum: Fragrances, between stink and fragrance , Vieweg + Teubner Verlag (2011) pp. 61–62, ISBN 978-3-8348-1245-2 .
↑ CANELLAKIS ES, TARVER H: The metabolism of methyl mercaptan in the intact animal . In: Arch. Biochem. Biophys. . 42, No. 2, February 1953, pp. 446-55. PMID 13031644 .
↑ Tschöpe W, Ritz E: Sulfur-containing amino acids are a major determinant of urinary calcium . In: Miner Electrolyte Metab . 11, No. 3, 1985, pp. 137-9. PMID 4010645 .
↑ MAZEL P, HENDERSON JF, AXELROD J: S-DEMETHYLATION BY MICROSOMAL ENZYMES . In: J. Pharmacol. Exp. Ther. . 143, January 1964, pp. 1-6. PMID 14112303 .
↑ Torsten Schmiermund: The chemical knowledge for the fire brigade , Springer Spectrum, ISBN 978-3-662-56605-3 , p. 585.
↑ Thomas A. Unger: Pesticide Synthesis Handbook . William Andrew, 1996, ISBN 0-8155-1853-6 , pp. 1040 ( limited preview in Google Book search).
↑ Hans-Dieter Jakubke, Hans Jeschkeit: amino acids, peptides, proteins , Verlag Chemie, Weinheim, p. 53, 1982, ISBN 3-527-25892-2 .
↑ Bernd Hoppe, Jürgen Martens : Amino acids - production and extraction , chemistry in our time , 18th year 1984, No. 3, pp. 73–86, doi : 10.1002 / ciuz.19840180302 .

[GESTIS-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Entry on methanethiol in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .

[CLP_100.000.748-2] Entry on methanethiol in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .

[3] Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for 74-93-1 or methanethiol ), accessed on November 2, 2015.

[CRC90_5_20-4] David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-20.

[5] Hans Beyer, Wolfgang Walter: Textbook of organic chemistry . 18th edition. S. Hirzel Verlag, Stuttgart 1978, ISBN 3-7776-0342-2 , p. 135 .

[6] Entry on methanethiol. In: Römpp Online . Georg Thieme Verlag, accessed on July 7, 2019.

[Legrum-7] Wolfgang Legrum: Fragrances, between stink and fragrance , Vieweg + Teubner Verlag (2011) pp. 61–62, ISBN 978-3-8348-1245-2 .

[8] CANELLAKIS ES, TARVER H: The metabolism of methyl mercaptan in the intact animal . In: Arch. Biochem. Biophys. . 42, No. 2, February 1953, pp. 446-55. PMID 13031644 .

[9] Tschöpe W, Ritz E: Sulfur-containing amino acids are a major determinant of urinary calcium . In: Miner Electrolyte Metab . 11, No. 3, 1985, pp. 137-9. PMID 4010645 .

[10] MAZEL P, HENDERSON JF, AXELROD J: S-DEMETHYLATION BY MICROSOMAL ENZYMES . In: J. Pharmacol. Exp. Ther. . 143, January 1964, pp. 1-6. PMID 14112303 .

[„Schmiermund“-11] Torsten Schmiermund: The chemical knowledge for the fire brigade , Springer Spectrum, ISBN 978-3-662-56605-3 , p. 585.

[unger-12] Thomas A. Unger: Pesticide Synthesis Handbook . William Andrew, 1996, ISBN 0-8155-1853-6 , pp. 1040 ( limited preview in Google Book search).

[jakubkeHD-13] Hans-Dieter Jakubke, Hans Jeschkeit: amino acids, peptides, proteins , Verlag Chemie, Weinheim, p. 53, 1982, ISBN 3-527-25892-2 .

[Hoppe2-14] Bernd Hoppe, Jürgen Martens : Amino acids - production and extraction , chemistry in our time , 18th year 1984, No. 3, pp. 73–86, doi : 10.1002 / ciuz.19840180302 .