Iodomethane
Structural formula | ||||||||||||||||
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General | ||||||||||||||||
Surname | Iodomethane | |||||||||||||||
other names |
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Molecular formula | CH 3 I. | |||||||||||||||
Brief description |
colorless liquid with a pungent ethereal smell |
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External identifiers / databases | ||||||||||||||||
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properties | ||||||||||||||||
Molar mass | 141.94 g mol −1 | |||||||||||||||
Physical state |
liquid |
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density |
2.28 g cm −3 |
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Melting point |
−66 ° C |
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boiling point |
42 ° C |
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Vapor pressure |
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solubility |
poor in water (8.66 g l −1 at 20 ° C) |
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Dipole moment | ||||||||||||||||
Refractive index |
1.5304 |
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safety instructions | ||||||||||||||||
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MAK |
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Toxicological data | ||||||||||||||||
Thermodynamic properties | ||||||||||||||||
ΔH f 0 |
−13.6 ± 0.5 kJ mol −1 |
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As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C |
Iodomethane , outdated methyl iodide , is an organic halogen compound .
presentation
Iodomethane is formed in an exothermic reaction when iodine is added to a mixture of methanol and red phosphorus . The iodising reagent is phosphorus triiodide , which is formed in situ :
Alternatively, iodomethane can be made by reacting dimethyl sulfate with potassium iodide in the presence of calcium carbonate :
Methyl iodide / CH 3 I can be purified from iodine by distillation and subsequent washing with Na 2 S 2 O 3 .
Physical Properties
Iodomethane is a colorless, ethereal-smelling liquid at ambient temperature and normal pressure. The compound boils at 42.44 ° C. under normal pressure. According to Antoine, the vapor pressure function results from log 10 (P) = A− (B / (T + C)) (P in bar, T in K) with A = 4.1554, B = 1177.78 and C = −32.058 in the temperature range from 218 to 315.6 K or with A = 4.14897, B = 1223.831 and C = −20.179 in the temperature range from 315.6 to 521 K. The compound is hardly combustible. The explosion range is between 8.5% by volume (500 g / m 3 ) as the lower explosion limit (LEL) and 66% by volume (3870 g / m 3 ) as the upper explosion limit (UEL). The ignition temperature is 355 ° C. The substance therefore falls into temperature class T2.
Chemical properties
Iodomethane reacts with alkali and alkaline earth metals and is used for the methylation (introduction of a methyl group ) of organic substances. Ammonia and amines react with iodomethane to form methylammonium iodides. By repeating this reaction, quaternary ammonium ions can be generated (so-called exhaustive methylation), whereby the amine is released with a base after each step:
Quaternary ammonium ions can no longer be deprotonated by alkalis . Their salts are completely dissociated .
Toxic properties
Iodomethane has been shown to be carcinogenic in animal experiments .
Physiological effect
Like other methylation reagents (example: dimethyl sulfate ), iodomethane is carcinogenic and very toxic . The carcinogenic effect is causally linked to the methylating effect. Methyl iodide is a very good electrophile and therefore easily enters into nucleophilic substitution reactions with the body's own nucleophiles . This leads to a methylation of the DNA , which can then no longer be read correctly by the DNA polymerase during cell division .
Reactions
Monsanto trial
Iodomethane is part of the Monsanto catalytic cycle for the production of acetic acid .
use
Disodium methyl arsonate can be obtained by reacting with sodium arsenite in the presence of sodium hydroxide .
Individual evidence
- ↑ a b c d e f g h i j k l Entry on iodomethane in the GESTIS substance database of the IFA , accessed on May 15, 2019(JavaScript required) .
- ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Permittivity (Dielectric Constant) of Gases, pp. 6-188.
- ↑ a b c Entry on iodomethane. In: Römpp Online . Georg Thieme Verlag, accessed on September 19, 2014.
- ↑ Entry on Iodomethane 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 74-88-4 or iodomethane ), accessed on November 2, 2015.
- ↑ AS Carson, PG Laye, JB Pedley, Alison M. Welsby: The enthalpies of formation of iodomethane, diiodomethane, triiodomethane, and tetraiodomethane by rotating combustion calorimetry , in: The Journal of Chemical Thermodynamics , 1993 , 25 (2) , p. 261-269; doi : 10.1006 / jcht.1993.1025 .
- ^ A b CS King, WW Hartman: Methyl Iodide In: Organic Syntheses . 13, 1933, p. 60, doi : 10.15227 / orgsyn.013.0060 ; Coll. Vol. 2, 1943, p. 399 ( PDF ).
- ↑ Boublik, T .; Aim, K .: Heats of Vaporization of Simple Non-spherical Molecule Compounds in Collect. Czech. Chem. Commun. 37, 3513 (1972).
- ^ A b Stull, DR: Vapor Pressure of Pure Substances. Organic and Inorganic Compounds in Ind. Eng. Chem. 39 (1947) 517-540, doi : 10.1021 / ie50448a022 .
- ^ A b E. Brandes, W. Möller: Safety-related parameters - Volume 1: Flammable liquids and gases , Wirtschaftsverlag NW - Verlag für neue Wissenschaft GmbH, Bremerhaven 2003.
- ↑ Carsten Schmuck, Bernd Engels, Tanja Schirmeister, Reinhold Fink: Chemistry for Medicine , Pearson Studies, p. 457, ISBN 978-3-8273-7286-4 .
- ↑ Greener Industry: Ethanoic Acid - Production Method: The Monsanto Process. Accessed May 14, 2019 .
- ^ PH List, L. Hörhammer: Chemicals and Drugs Part A: NQ . Springer-Verlag, 2013, ISBN 978-3-642-65035-2 , pp. 108 ( limited preview in Google Book search).