Thiophosphoric acid
| Structural formula | ||||||||||
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| General | ||||||||||
| Surname | Thiophosphoric acid | |||||||||
| other names |
Monothiophosphoric acid |
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| Molecular formula | H 3 PO 3 S | |||||||||
| Brief description |
clear liquid |
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| properties | ||||||||||
| Molar mass | 114.06 g · mol -1 | |||||||||
| Physical state |
liquid |
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| Melting point |
−60 ° C |
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| solubility |
hydrolyzes in water to form hydrogen sulfide and phosphoric acid |
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| safety instructions | ||||||||||
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||
Thiophosphoric acid is an unstable chemical compound from the group of phosphorus compounds . It is a derivative of phosphoric acid in which an oxygen atom has been replaced by a sulfur atom (hence the prefix thio- ). If more than one oxygen atom is replaced, dithiophosphoric acid , trithiophosphoric acid or tetrathiophosphoric acid are formed accordingly .
Extraction and presentation
According to R. Klement, thiophosphoric acid can be obtained by reacting barium dithiophosphate with sulfuric acid and subsequent hydrolysis of the resulting dithiophosphoric acid to form monothiophosphoric acid.
properties
Thiophosphoric acid can be stored as a concentrated acid (up to 83% concentration) in the absence of air at temperatures below −2 ° C and remains clear. When exposed to air, it becomes clouded by precipitating sulfur, which is formed by the oxidation of the hydrogen sulfide formed by the gradual hydrolysis of monothiophosphoric acid . When the concentrated acid is heated to 40 ° C, hydrogen sulfide is violently developed. The acid solidifies below −60 ° C.
Derivatives
Ester
Some compounds derived from thiophosphoric acid, such as its esters, are of great importance . They are practically derivatives of (mostly aromatic ) phosphoric acid esters in which one ( thiophosphoric acid ester ) or more oxygen atoms ( dithiophosphoric acid ester , trithiophosphoric acid ester and tetrathiophosphoric acid ester) are replaced by sulfur. Many of them are highly toxic because, like other phosphoric acid esters, the enzyme cholinesterase , which has an essential function in the central nervous system , is inhibited. They are often used as insecticides and acaricides (e.g. Chlorpyrifos , Dimethoat , Parathion , Azamethiphos ), as cytostatics (e.g. Thiotepa ), but also as nerve agents (e.g. VX ). The first thiophosphoric ester insecticides were introduced to the market in the 1950s.
Examples of thiophosphoric acid esters:
- Chlorthiophos C 11 H 15 Cl 2 O 3 PS 2
- Cythioate C 8 H 12 NO 5 PS 2
- Demephion C 5 H 13 O 3 PS 2
- Diazinon C 12 H 21 N 2 O 3 PS
- Dioxathione C 12 H 26 O 6 P 2 S 4
- Fensulfothione C 11 H 17 O 4 PS 2
- Fenthion C 10 H 15 O 3 PS 2
- Malathion C 10 H 19 O 6 PS 2
- Parathion C 10 H 14 NO 5 PS
- Phorate C 7 H 17 O 2 PS 3
Salts
In addition to the thiophosphoric acid esters, there are also salts of thiophosphoric acid, which are known as thiophosphates (also phosphorothioates with the anions PO 3 S 3− to PS 4 3− ), such as sodium monothiophosphate , which is used for chemical syntheses.
Examples of thiophosphates:
- Sodium monothiophosphate Na 3 PO 3 S
- Sodium dithiophosphate Na 3 PO 2 S 2
- Barium dithiophosphate Ba 3 (PO 2 S 2 ) 2
See also
Individual evidence
- ↑ a b c d e Georg Brauer (Ed.), With the collaboration of Marianne Baudler u. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 .
- ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
- ↑ Memorandum: Organophosphate Pesticides (PDF; 739 kB).