Trimethyl phosphite

Structural formula
General
Surname	Trimethyl phosphite
other names	Phosphorous acid trimethyl ester TMPI
Molecular formula	C 3 H 9 O 3 P
Brief description	colorless, pyridine-like (pungent in lower concentrations) smelling liquid
External identifiers / databases
CAS number 121-45-9 EC number 204-471-5 ECHA InfoCard 100.004.065 PubChem 8472 Wikidata Q153418
properties
Molar mass	124.08 g mol −1
Physical state	liquid
density	1.05 g cm −3 (20 ° C)
Melting point	−78 ° C
boiling point	111 ° C (1013 hPa)
Vapor pressure	28 h Pa (20 ° C) 43 hPa (30 ° C) 99 hPa (50 ° C)
solubility	Decomposes in water
Refractive index	1.4095 (20 ° C)
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 226-302-315-319 EUH: 014 P: 210-302 + 352-305 + 351 + 338
MAK	Switzerland: 2 ml m −3 or 10 mg m −3
Toxicological data	1600 mg kg −1 ( LD 50 ,  rat ,  oral )
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

Trimethyl phosphite (TMPI) or phosphorous acid trimethyl ester is a colorless, foul-smelling, poisonous liquid that belongs to the group of phosphites . It may, for example, in the Arbuzov reaction for the preparation of phosphonates and in the perkow reaction for synthesis of vinyl phosphonates are used.

Presentation and extraction

Trimethyl phosphite can easily be obtained by reacting phosphorus trichloride with methanol .

properties

Physical Properties

Trimethylphosphite is a colorless liquid that boils at 111 ° C under normal pressure . The vapor pressure function results according to Antoine according to ln (P) = A− (B / (T + C)) (P in Pa, T in K) with A = 20.15306, B = 2519.7227 and C = −89, 44893 in the temperature range from 302 to 343 K.

Trimethyl phosphite forms highly flammable vapor-air mixtures. The compound has a flash point at 23 ° C. The explosion range is between 5.2 vol.% As the lower explosion limit (LEL) and 61.2 vol.% As the upper explosion limit (UEL). The ignition temperature is 250 ° C. The substance therefore falls into temperature class T3. Violent decomposition occurs on contact with water.

Chemical properties

By reacting with alkyl halides, the corresponding phosphonic acid esters can be obtained in an Arbuzov reaction .

This type of reaction can be initiated thermally or catalytically as isomerization to dimethyl methanephosphonate. This reaction proceeds with a heat of reaction of −180.7 kJ mol ⁻¹ or −1456 kJ kg ^−1, strongly exothermic, which can be explosive in an uncontrolled manner . In an incident on December 1, 2014 at Schill & Seilacher Chemie GmbH in Pirna , 5 tons of trimethylphosphite leaked, with one fatality and four injuries as well as property damage of several million euros.

In a Perkow reaction , organic vinyl phosphates are formed with α – halogen ketones.

According to Corey-Winter, the corresponding alkenes can be obtained from 1,2-diols in a two-step synthesis after reaction with thiophosgene to give the thiocarbonate and subsequent reduction with trimethyl phosphite . The degradation step of the thiocarbonate intermediate is stereoselective. Thus, the cis-alkenes result from the cis-1,2-diols and the trans-alkenes from trans-1,2-diols result in good yield.

Thermal decomposition takes place above 200 ° C with the formation of hydrogen phosphide , methanol , phosphorous acid and other phosphorus compounds. The compound reacts violently and with strong heat generation with water and acids. Highly flammable methanol is formed during hydrolysis . Contact with magnesium perchlorate (e.g. as a desiccant) leads to the formation of explosive methyl perchlorate .

use

The compound is used as a methylating and phosphorylating agent, especially in the synthesis of insecticides and herbicides . used.

Individual evidence

1. ↑ ^{a b c d e f g h i j k l m n o} Entry on trimethyl phosphite in the GESTIS substance database of the IFA , accessed on May 5, 2020(JavaScript required) .
2. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-510.
3. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for 121-45-9 or trimethylphosphite ), accessed on November 2, 2015.
4. ↑ ^{a b} entry on trimethyl phosphite. In: Römpp Online . Georg Thieme Verlag, accessed on August 7, 2012.
5. ↑ Dutt, NVK; Kahol, AP; Jyothiraju, P .: Vapor Pressure of Trimethyl Phosphite and Triethylamine in J. Chem. Eng. Data 27 (1982) 389-370, doi: 10.1021 / je00030a001 . Adaptation of the measurement data according to Antoine by the processor
6. ↑ ^{a b c} e-EROS Encyclopedia of Reagents for Organic Synthesis , 1999-2013, John Wiley and Sons, Inc., entry for Trimethyl phosphite, accessed August 8, 2013 .
7. ↑ Regenass, W .: Thermoanalytical methods in chemical process development in Thermochim. Acta 20 (1977) 65-79, doi : 10.1016 / 0040-6031 (77) 85041-7 .
8. ^ Regenass, W .: Calorimetric Monitoring of Industrial Chemical Processes in Thermochim. Acta 95 (1985) 351-368, doi : 10.1016 / 0040-6031 (85) 85296-5 .
9. ↑ IChemE Symposium series no. 102: Pressure Hazards - Hazards from Pressure: Exothermic Reactions, Unstable Substances, Pressure Relief and Accidental Discharge, 1987, S102-21, Bourne, JR; Brogli, F .; Hoch, F .; Regenass, W .: Heat transfer from exothermically reacting fluid in vertical unstirred vessels .
10. ↑ Federal Environment Agency - Central reporting and evaluation point for incidents and malfunctions in process engineering systems (ZEMA), annual report 2012-2014, pages 223-225, pdf
11. ↑ ^{a b c} Roth / Weller: Hazardous chemical reactions , ecomed SECURITY, publishing group Hüthig Jehle Rehm GmbH, edition 08/2011.