 | |
 | |
| Names | |
|---|---|
| Preferred IUPAC name O1,O1,O3,O3-Tetraethyl 1,3-dithiodiphosphate | |
| Other names | |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| DrugBank | |
| ECHA InfoCard | 100.020.905 |
| EC Number |
|
| RTECS number |
|
| UNII | |
| UN number | 1704 |
| |
| |
| Properties | |
| C8H20O5P2S2 | |
| Molar mass | 322.31 g·mol−1 |
| Appearance | Pale yellow liquid[3] |
| Odor | Garlic-like[3] |
| Density | 1.196 g/cm3 |
| Boiling point | 136 to 139 °C (277 to 282 °F; 409 to 412 K) at 2 mm Hg |
| 30 mg/L | |
| Vapor pressure | 0.0002 mmHg (20°C)[3] |
| Hazards[6][7] | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Poison[4] |
| GHS labelling:[1] | |
  | |
| Danger | |
| H300,H310,H410 | |
| P262,P264,P270,P273,P280,P301+P316,P302+P352,P316,P321,P330,P361+P364,P391,P405,P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | −18 °C (0 °F; 255 K) |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 22 mg/kg (mouse, oral) 25 mg/kg (rabbit, oral) 5 mg/kg (dog, oral) 5 mg/kg (rat, oral)[5] |
LC50 (median concentration) | 38 mg/m3 (rat, 4 hr) 40 mg/m3 (mouse, 4 hr)[5] |
| NIOSH (US health exposure limits): | |
PEL (Permissible) | TWA 0.2 mg/m3 [skin][3] |
IDLH (Immediate danger) | 10 mg/m3[3] |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Sulfotep (also known astetraethyldithiopyrophosphate andTEDP[8]) is a pesticide commonly used in greenhouses as afumigant. The substance is also known as Dithione, Dithiophos, and many other names. Sulfotep has the molecular formula C8H20O5P2S2 and belongs to theorganophosphate class of chemicals. It has acholinergic effect, involving depression of thecholinesterase activity of the peripheral and central nervous system of insects.[7] The transduction of signals is disturbed at the synapses that make use ofacetylcholine. Sulfotep is a mobileoil that is pale yellow-colored and smells likegarlic.[8][9] It is primarily used as aninsecticide.
Sulfotep was first commercially launched by Bayer in 1946. The first time that tetraethyl dithiopyrophosphate was registered to be used in theUnited States was in 1951. A Registration Standard for the chemical was issued by theEnvironmental Protection Agency in September 1988. Plans were made in 1999 by the Environmental Protection Agency to stop production of it by September 30, 2002, and to outlaw the use and distribution of products containing it by September 30, 2004.[10]
Sulfotep is synthesized by a reaction oftetraethyl pyrophosphate (TEPP) with sulfur. TEPP itself was first synthesized by Wladimir Moschnin[11] andPhilippe de Clermont in 1854.[12] TEPP is made by a reaction ofdiethyl chlorophosphate with water to substitute the chloro group with a hydroxyl group. The product can react with another molecule of diethylchlorophosphate to form the ester, TEPP. In this reaction,pyridine is often used to neutralize thehydrochloric acid byproduct.[13]
An alternative route to TEPP can be a reaction of diethyl chlorothiophosphate an aqueous solution ofsodium bicarbonate (Na2CO3).
When heated to a temperature that is high enough for sulfotep todecompose, it gives offfumes ofphosphorus andsulfur oxides, which are highly toxic.[8][9] It canexplode if containers of it are heated, and it can burn, although it does not do so easily. The chemical can alsopolymerize explosively.[14] The chemical also reacts to formtoxic andflammable gases in the presence ofhydrides and otherreducing agents. It is able to corrodeiron.[9] When it does this, it can release hydrogen gas.[14] The chemical has aspecific gravity of 1.196 at 77 °F (25 °C) and its vapor density is 13.17 grams per liter at 25 °C (77 °F).[9][15] Itsmelting point is 88 °C (190 °F) and itsboiling point is between 272 °F (133 °C) and 282 °F (139 °C) at 2 mmHg.[8][9] The chemical'ssorption coefficient is 2.87 Log L/kg. ItsHenry's Law constant is 0.000175 at 20 °C (68 °F). Itsoctanol-water partition coefficient is 3.9804 Log L/kg. Tetraethyl dithiopyrophosphate's diffusion coefficient in air is 0.015 cm2 per second and its diffusion coefficient in water is 0.0000055 cm2.[16]
Sulfotep'sflash point is 178 °C (352 °F) and itsenthalpy of vaporization is 59.4 kilojoules permole. Itssurface tension is 423dynes per centimeter.[citation needed] The chemical has noRule of 5 violations.[17] Itsdiffusivity in water is 0.63 × 10−5 cm2 per second. It ismiscible with a large number oforganic solvents, includingmethyl chloride andacetone[18] and its solubility in water is 30 milligrams per liter at 20 °C (68 °F).[15]
The alkaline and neutralhydrolysis of sulfotep results in the release ofethanol,phosphoric acid, andhydrogen sulfide.[19]
Sulfotep has applications as aninsecticide,miticide, andacaricide.[9] However, because it does not leave behind a residue, it is less effective at these roles thanDDT.[20] However, it is about as effective as the insecticideparathion.[21] Its use is restricted togreenhouses andornamental plants. When the chemical is used as an insecticide, it is in the form of an impregnated smoke fumigant.[10] Sulfotep is used in greenhouses as a fumigant formulation to control aphids, spider mites, whiteflies and thrips. It is formulated as impregnated material in smoke generators containing 14 to 15% active ingredient. Smoke generators are placed in the greenhouses and then ignited using inserted sparklers to generate a thick white smoke for fumigation.
Sulfotep killsspider mites,mealybugs,whiteflies, andaphids. However, the chemical is notphytotoxic, unliketetraethyl pyrophosphate.[22] However, it occasionally causes minor damage to plants, such as the slight puckering and cupping of leaves.[23] During several tests in the late 1940s, it was found to be the most toxic of several chemicals to whiteflies onvegetables, two-spotted spider mites onroses, and mealybugs on numerous plants.[22]
A mixture containing 5% sulfotep at the concentration of 0.5 grams of phosphate per 1000 cubic feet was found in tests in the late 1940s to kill 100% of nonresistant two-spotted spider mites and 68-97% of resistant two-spotted spider mites. Sulfotep aerosols killed 100% of the populations of a large number of insects, but only killed 98% of mealybugs in the same tests.[20] 88% of nonresistant spider mites can be killed be two minutes of exposure to a mixture containing 5% of the chemical, 98-99% can be killed after five to ten minutes, and all can be killed after 15 minutes.[23]
Sulfotep, just as allorganophosphate pesticides, irreversibly inactivatesacetylcholinesterase, which is essential to nerve function in insects, humans, and many other animals. Acetylcholinesterase normally hydrolyses acetylcholine after it was released in the synapse. When the acetylcholine is not degraded, it accumulates in the synaptic cleft. Thus, it keeps on stimulating the nerve.[24]
Sulfotep is taken up well both orally, dermally as well as through inhalation. A few different organizations determined a maximum concentration sulfotep in the air. The maximum allowed concentration is 0.2 mg/m3.
Sulfotep is desulfurated by eithercytochrome P450 or the FAD-containing monooxygenases. In this reaction, the sulfur is replaced by oxygen, as seen in figure 2. The metabolites formed are monosulfotep and tetraethyl pyrophosphate (TEPP). To accomplish these reactions, a phospho-oxithirane ring is formed, which is highly reactive. This ring is thought to bind to acetylcholinesterase and cause toxicity.[25]
The two Phase I metabolites are further transformed through a hydrolysis-reaction mediated by a type A-esterase. The products formed areO,O-diethyldithiophosphate andO,O-diethylphosphate.[25]
An experiment in rats who were once given 0.4 mg radioactive phosphor-labelled sulfotep orally, has shown that sulfotep is excreted by both the kidneys (urine) and the liver (bile). The substance is completely metabolised. Two metabolites are found in the urine and faeces. The radioactivity showed that 85-91% was excreted in urine and 5-6% in the faeces.[24]
Sulfotep is toxic to some wildlife, includingfish andaquatic invertebrates. It is also assumed by the Environmental Protection Agency to be toxic tobirds.[10]
| Exposure | Toxic level |
|---|---|
| Inhalation | mg/m3 |
| Mouse 1 hr | 155[2][26] |
| Mouse 4 hr | 40[2][26] |
| Rat 1 hr | 160-330[2][26] |
| Rat 4 hr | 38-59[2][26] |
| Oral LD50 | mg/kg |
| Cat | 3[2][26][27] |
| Dog | 5[2][26][27] |
| Mouse | 21.5-29.4[2][26][27] |
| Rabbit | 25[2][26][27] |
| Rat | 5-13.8[2][26][27] |
| Dermal LD50 | mg/kg |
| Rat 4 hr | 262[2] |
| Rat 7 d | 65[2] |
| Intravenous LD50 | μg/kg |
| Mouse | 300[2][27] |
| Intramuscular LD50 | μg/kg |
| Mouse | 500[2][27] |
| Rat | 55[2][27] |
| Intraperitoneal LD50 | μg/kg |
| Mouse | 940[2][27] |
| Rat | 6600[2][27] |
| Subcutaneous LD50 | mg/kg |
| Mouse | 8[2][27] |
Surviving animals completely recovered in 1–4 days.
A long-term exposure to a low concentration showed no toxicity.This was tested in rats. They were exposed to different concentrations of sulfotep. Exposed to the highest concentration of 2.83 mg/m3 for six hours a day, five days a week for 12 weeks, there was no change in appearance, behavior or body weight. The plasma cholinesterase activity decreased and the weight of the lungs of female rats increased. The red blood cell acetylcholinesterase activity was not affected. At lower concentrations, there were no changes at all.
The rats were orally exposed to 0, 5, 10, 20 or 50 ppm sulfotep for three months. Only their plasma cholinesterase activity and RBC acetylcholinesterase activity were decreased. No further symptoms were observed.Dogs who were orally exposed to 0, 0.5, 3, 5, 15 or 75 ppm (equivalent to 0–3.07 mg/kg/day) for 13 weeks, ate less and lost weight. The plasma cholinesterase activity was already affected by a sulfotep concentration of 3 ppm (or higher). Red blood cell-acetylcholinesterase was decreased at 75 ppm. Diarrhea and vomiting occasionally occurred at 15 ppm, but were common at 75 ppm. The brain cholinesterase activity was unaffected.[26]
According to theOccupational Safety and Health Administration, the upper limit on exposure of sulfotep to human skin is 0.2 milligrams per cubic meter.[14]
Sulfotep causes an organophosphate poisoning. This means that it had an effect on the activity of cholinesterase. There are differences for the indications of a sulfotep poisoning between inhalation, ingestion, intake by the skin and intake by the eyes. However, examples of poisoned greenhouse workers teach us an overall route of symptoms for a sulfotep poisoning. Within the first hour after a poisonous intake of sulfotep people often suffer from nausea or headaches. After some hours diarrhea and vomiting may occur. People who inhaled sulfotep are often disorientated and have difficulties to breathe. A poisonous dose may lead to a coma or death after 24 hours. The point at 24 hours after the poisoning is very important. If the dose is not lethal, the symptoms will slowly disappear after the point of 24 hours.[28][29]
No embryotoxic or teratogenic effects occurred in tests. Neither were there any signs for carcinogenic effects. It was only mutagenic in one strain ofS. typhimurium. In four other bacterial strains as well as in rats and mice it was not mutagenic at all.
There are two cases of acute toxicity known in man. The cholinesterase activity in these people was reduced. It took them 20 respectively 28 days to recover.[26]The most important poisoning symptoms are shown in the following table.[30]
| Exposure | Symptoms | First aid treatment | Other treatments |
|---|---|---|---|
| Inhalation | blue skin, convulsions, dizziness, drowsiness, headache, sweating, labored breathing, nausea, unconsciousness, weakness | Fresh air or artificial respiration. Rest is important to prevent a respiration-arrest | |
| Ingestion | cramps in intestines, diarrhea, vomiting, confusion | Vomiting may only be induced in conscious people | Active charcoal to absorb compound.Atropine as an antidote |
| Eyes | irritation, redness, constriction of the pupil, loss of focus | Rinsing with plenty of water will lead to recovery of sight within 24 hours | |
| Skin (may be absorbed) | redness, irritation, sweating, twitching of the area | First rinse with plenty of water. Then wash the skin with water and soap |
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