Tetraethyl pyrophosphate

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Tetraethyl pyrophosphate
Skeletal formula
Ball-and-stick model
Names
Preferred IUPAC name
Tetraethyl diphosphate
Identifiers
3D model (
JSmol
)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard
 100.003.179 Edit this at Wikidata
EC Number
  • 203-495-3
KEGG
RTECS number
  • UX6825000
UNII
UN number 3018 2783
  • InChI=1S/C8H20O7P2/c1-5-11-16(9,12-6-2)15-17(10,13-7-3)14-8-4/h5-8H2,1-4H3 checkY
    Key: IDCBOTIENDVCBQ-UHFFFAOYSA-N checkY
  • InChI=1/C8H20O7P2/c1-5-11-16(9,12-6-2)15-17(10,13-7-3)14-8-4/h5-8H2,1-4H3
    Key: IDCBOTIENDVCBQ-UHFFFAOYAI
  • O=P(OP(=O)(OCC)OCC)(OCC)OCC
Properties
C8H20O7P2
Molar mass 290.189 g·mol−1
Appearance colorless to amber liquid[1]
Odor faint, fruity[1]
Density 1.19 g/mL (20°C)[1]
Melting point 0 °C; 32 °F; 273 K[1]
Boiling point decomposes[1]
miscible[1]
Vapor pressure 0.0002 mmHg (20°C)[1]
Hazards
GHS labelling:
GHS06: ToxicGHS08: Health hazard
Danger
H300, H310, H400
P262, P264, P270, P273, P280, P301+P310, P302+P350, P310, P321, P322, P330, P361, P363, P391, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
4
1
1
Lethal dose or concentration (LD, LC):
0.5 mg/kg (rat, oral)
2.3 mg/kg (guinea pig, oral)
3 mg/kg (mouse, oral)[2]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 0.05 mg/m3 [skin][1]
REL (Recommended)
 TWA 0.05 mg/m3 [skin][1]
IDLH
(Immediate danger)
 5 mg/m3[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Tetraethyl pyrophosphate, abbreviated TEPP, is an

organophosphate compound with the formula [(C2H5O)2P(O)]2O. It is the tetraethyl derivative of pyrophosphate (P2O74-). It is a colorless oil that solidifies near room temperature. It is used as an insecticide. The compound hydrolyzes rapidly.[3]

Applications

TEPP is an insecticide to aphids, mites, spiders, mealybugs, leafhoppers, lygus bugs, thrips, leafminers, and many other pests.[4] TEPP and other organophosphates are the most widely used pesticides in the U.S. due to their effectiveness and relative small impact on the environment because this organophosphate breaks down so easily.

TEPP has been used for treatment for myasthenia gravis, an autoimmune disease. The treatment would deliver an increase in strength.[5]

Synthesis

The synthesis by De Clermont and Moschnin was based on the earlier work by Alexander Williamson (who is well known for the Williamson-synthesis of ethers).[6] Their synthesis made use of ethyl iodide and silver salts to form esters in combination with pyrophosphate.[7]

Ag4P2O7 + 4EtI → [(EtO)2P(O)]2O + 4AgI

Commercial routes to TEPP often use methods developed by Schrader, Woodstock, and Toy.

phosphorus oxychloride (Schrader-method) or phosphorus pentoxide (Woodstock-method).[8][9] Alternatively, controlled hydrolysis of diethyl phosphorochloridate delivers the compound:[10][11]

2(EtO)2P(O)Cl + H2O → [(EtO)2P(O)]2O + 2HCl

The related tetrabenzylpyrophosphate is prepared by dehydration of dibenzylphosphoric acid:[12]

2(RO)2P(O)OH → [(EtO)2P(O)]2O + H2O

Hydrolysis

TEPP and most of the other organophosphates are susceptible to hydrolysis.[13] The product is diethyl phosphate.[13][14]

Toxicity

TEPP is bioactive as an

acetyl choline
.

TEPP is highly toxic for all warm-blooded animals, including humans.[15] There are three types of effects on these animals that have come forward during laboratory studies.

  • DERMAL: LD50 = 2.4 mg/kg (male rat)
  • ORAL: LD50 = 1.12 mg/kg (rat)[4]

Death is mostly due to either respiratory failure and in some cases cardiac arrest. The route of absorption might be responsible for the range of effect on certain systems.[16]

For cold-blooded animals the effects are slightly different. In a study with frogs, acute exposure caused a depression in the amount of erythrocytes in the blood. There was also a reduction of white bloodcells, especially the neutrophil granulocytes and lymphocytes. There was no visible damage to the bloodvessels to explain the loss of blood cells. Further there were no signs like hypersalivation or tears like in warm-blooded animals, though there was hypotonia leading to paralysis.[17]

History

It was first synthesized by

Adolphe Wurtz. A fellow student Philippe de Clermont is often incorrectly credited as the discoverer of TEPP despite his recognition of the Moschnin primacy in two publications.[18]

The ignorance about the potential

organophosphorus chemistry has really started developing with the help of A. W. von Hofmann, Carl Arnold August Michaelis and Aleksandr Arbuzov.[19]

It was not until 1932 before the first adverse effects of compounds similar to TEPP had been recognized. Willy Lange and Gerda von Krueger were the first to report such effects, about which the following statement was published in their article (in German):[20]

"Interestingly, we report the strong effect of monofluorophosphate phosphoric acid alkyl esters on the human organism. The vapor of these compounds have a pleasant odor and sharply aromatic. After only a few minutes of inhaling the vapor, there is a strong pressure on the larynx, associated with shortness of breath. Then comes decreased awareness, opacities, and dazzling phenomena causing painful sensitivity of the eye to light. Only after several hours is there relief from these phenomena. They are apparently not caused by acidic decomposition products of the ester, but they are probably due to the Dialkyl monofluorophosphates themselves. The effects are exerted by very small amounts."

Starting in 1935 the German government started gathering information about new toxic substances, of which some were to be classified as secret by the German Ministry of Defence.[19] Gerhard Schrader, who has become famous for his studies into organophosphorus insecticides and nerve gases, was one of the chemists who was also studying TEPP. In his studies, in particular his studies into the biological aspects, he noticed that this reagent could possibly be used as an insecticide. This would make the classification of the compound as secret disadvantageous for commercial firms.[19]

Around the beginning of the

anticholinesterase
activity of TEPP.

After the Second World War, Schrader was among many German scientists who were interrogated by English scientists, among others. During the war, the English had been developing chemical weapons of their own to surprise their enemies. In these interrogations the existence of TEPP and other insecticides were disclosed. The existence of nerve gases, however also being disclosed by Schrader, was kept secret by the military.[10]

References

  1. ^ a b c d e f g h i j NIOSH Pocket Guide to Chemical Hazards. "#0590". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ "TEPP". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  3. ISBN 978-3527306732
    .
  4. ^
    doi:10.1093/jee/48.2.157
    .
  5. ISSN 0002-9394
    .
  6. ^
    PMID 19435147
    .
  7. doi:10.31482/mmsl.2015.023
    .
  8. ISBN 978-1-4832-2084-0
    .
  9. ^ National Research Council (U S. ) Pesticide Residues Committee (1965). Report on "no Residue" and "zero Tolerance". National Academies. pp. 3–4.
  10. ^
    PMID 18102975
    .
  11. doi:10.1021/jo01149a031
    .
  12. doi:10.15227/orgsyn.080.0219
    .
  13. ^
    PMID 11869832
    .
  14. PMID 11543910
    .
  15. ^ "Benfluralin - National Library of Medicine HSDB Database". toxnet.nlm.nih.gov. Retrieved 2016-03-08.
  16. ^ Clarke, Myra L.; Harvey, Douglas Graham; Humphreys, David John (1988). Veterinary Toxicology (2 ed.). London, England: Bailliere Tindal. p. 157.
  17. PMID 4284682
    .
  18. S2CID 33095322.The history of cholinesterase inhibitors: who was Moschnin(e)?
  19. ^
    ISBN 978-3-642-99875-1
    .
  20. PMID 21105582
    .
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