Perchloromethyl mercaptan

Perchloromethyl mercaptan
Skeletal formula of perchloromethyl mercaptan
Space-filling model of the perchloromethyl mercaptan molecule
Names
Preferred IUPAC name
Perchloromethyl mercaptan
Other names
Trichloromethane sulfenyl chloride

Trichloromethyl sulfur chloride

Clairsit
Identifiers
594-42-3 N
ChemSpider 11176 YesY
EC Number 209-840-4
Jmol interactive 3D Image
PubChem 11666
Properties
CCl4S
Molar mass 185.87 g·mol−1
Appearance Oily, yellow liquid
Odor disagreeable, acrid odor
Density 1.72 g/cm3
Melting point −44 °C (−47 °F; 229 K)
Boiling point 147 to 148 °C (297 to 298 °F; 420 to 421 K)
insoluble
log P 3.47 (estimated)
Vapor pressure 0.4 kPa (at 20 °C)
Hazards
T N
R-phrases R21 R25 R26 R34
S-phrases S25 S28 S36/37/39 S45
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazards (white): no codeNFPA 704 four-colored diamond
0
3
2
Lethal dose or concentration (LD, LC):
82.6 mg/kg (rat, oral)[1]
11 ppm (rat, 1 hr)
16 ppm (rat, 1 hr)
9 ppm (mouse, 3 hr)
38 ppm (mouse, 2 hr)
11 ppm (rat, 1 hr)[1]
388 ppm (human, 10 min)
46 ppm (mouse, 10 min)[1]
US health exposure limits (NIOSH):
TWA 0.1 ppm (0.8 mg/m3)[2]
TWA 0.1 ppm (0.8 mg/m3)[2]
10 ppm[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Perchloromethyl mercaptan, CCl3SCl, is mainly used as an intermediate for the synthesis of dyes and fungicides (captan, folpet). It is an oily, pale yellow liquid, which is insoluble in water, with a foul-smelling, unbearable, acrid odor. When it is heated or in a fire, it will emit toxic and corrosive gases. It is also very toxic by inhalation or skin absorption.[3]

History

Perchloromethyl mercaptan was discovered by the German chemist B. Rathke around 1870. He is credited with the assignment of the correct structure of this compound, a method for its preparation which is still used commercially, and a number of studies dealing with its chemistry. Since Rathke, a number of other chemists have studied this remarkable compound. Rathke’s influence is still felt in the later work. Perchloromethyl mercaptan received little industrial attention until recently, when A. R. Kittleson discovered the tetrahydrophthalimide derivative. This derivative, commercially known as Captan, possesses fungicidal properties and is at present used in agriculture. Tricloromethanesulfenyl chloride itself is manufactured by several companies in the United States and Europe.

It was used as a chemical warfare agent by the French in the 1915 battle of Champagne. Shortly thereafter, wartime use was abandoned due to the clear warning properties, the decomposition in the presence of iron and steel, and the easy removal of the vapor by charcoal.[4]

Perchloromethyl mercaptan is the original name that was given to this chemical compound. The most common name is trichloromethanesulfenyl chloride, because the compound bears no similarity to mercaptans in either its chemical or its physical properties. For that reason trichloromethanesulfenyl is a more suitable name.[3][3]

Synthesis

The method to prepare perchloromethyl mercaptan was first described by Rathke in 1873[3] and is still used. Carbon disulfide is chlorinated using an iodine catalyst. The following equations operate most efficiently at temperatures below about 40 °C:

CS2 + 3 Cl2 → CCl3SCl + SCl2
2CS2 + 5 Cl2 → 2 CCl3SCl + S2Cl2
CS2 + 3 Cl2 → CCl4 + S2Cl2

The primary unwanted byproducts of this reaction are sulfur dichloride, sulfur chloride (sulfur monochloride) and carbon tetrachloride. The formation of byproducts can be suppressed by performing the reaction in the presence of molecules with two carbonyl groups, such as a diketone.[5] Other byproducts are thiophosgene and other compounds. It is possible to remove the more volatile byproducts such as carbon tetrachloride and sulfur dichloride from the reaction mixture by distillation. However, it is extremely difficult to separate perchloromethyl mercaptan from sulfur chloride by distillation, due to the fact that the boiling points of these two compounds are very close to each other. There are several methods known which improve on the basic Rathke method. At the moment the yield of the synthesis of perchloromethylmercaptan is being improved by using phosphonates and phosphonites as addictives.[5]

Reactivity and reactions

The compound is insoluble in water, and slowly decomposes by moisture in the air. It reacts with hot water to give carbon dioxide, hydrochloric acid and sulfur:[5]

CSCl4 + 2H2O → CO2 + 4HCl + S

Perchloromethylmercaptan is incompatible with acids, diazo and azo compounds, halocarbons, isocyanates, aldehydes, alkali metals, nitrides, hydrides, and other strong reducing agents. Reactions with these materials generate heat and in many cases hydrogen gas. It reacts readily with oxidizing agents. The compound is a fire hazard. Very irritating vapors are formed from hot material, which may form phosgene gas, hydrogen chloride, and sulfur dioxide. At high temperatures perchloromethyl mercaptan will decompose to carbon tetrachloride, sulfur chloride, heavy oil polymers, phosgene gas, hydrogen chloride, and sulfur dioxide. Hazardous polymerization may not occur.

Metals

The compound is corrosive to most metals. It reacts with iron or steel, evolving carbon tetrachloride:[4]

4Cl3CSCl → S2Cl2 + 2CCl4 + S2C2Cl6

Oxidation

Perchloromethyl mercaptan is oxidized by nitric acid to trichloromethanesulfonyl chloride (Cl3CSO2Cl), a white solid.[4]

Biological effects

Toxicity

At least two mechanisms could account for the toxicity of perchloromethyl mercaptan, as hypothesized by Althoff (1973). The first mechanism is a reaction between perchloromethyl mercaptan and biological functional groups such as hydroxyl, sulfhydryl, amino and carboxyl groups. This results in an inactivation of key enzymes.

R-NH2 + CCl3-S-Cl
R-OH + CCl3-S-Cl

The second reaction is the hydrolysis of perchloromethyl mercaptan. When the hydrolysis product hydrochloric acid is released, it immediately damages tissue.

CCl3SCl + H2O → CCl3-SOH + HCl

This rate-limiting step, resulting in trichlorosulphenic acid (CCl3-SOH), is the first step of this reaction. The trichlorosulphenic acid subsequently reacts to thiophosgene-S-oxide (Cl2C=S=O). The hydrochloric acid is presumably not formed in a large amounts, because of the insolubility of perchloromethyl mercaptan in water. When hydrochloric acid is evolved, however, there is likely to be deep lung damage. On the other hand, when animals are exposed to perchloromethyl mercaptan, the upper-respiratory-tract damage was not severe.[3]

Detoxification

Because of the similarities in reactivity of perchloromethyl mercaptan with captan, the metabolism and also the detoxification of both compounds will probably be the same. Perchloromethyl mercaptan is comparable with the trichloromethylthio moiety of captan (1,2,3,6-tetrahydro,N,(trichloromethylthio)-phthalimide). Reactions of this moiety with amino- or thiol groups yields via a number of steps the very reactive compound thiophosgene. It is apparent that thiophosgene also causes toxicity in the metabolism of perchloromethyl mercaptan. Thiophosgene can be detoxified in at least three ways:

  1. Condensation with either free or protein-bound cysteine to, ultimately, thiazolidine-2-thione-4-carboxylic acid (TTCA).
  2. Hydrolysis and/or oxidation to CO2 and H2S.
  3. Reaction with sulphite to a sulphonic acid and its monoxide derivative.[6]

Animal models

LD50/LC50 Table

Animal Oral Inhalation Intraperitoneal Intravenous Skin Eyes
Rat 82,6 mg/kg 11 ppm/1h 25 mg/kg
Mouse 400 mg/kg 296 g/m3/2h 10 mg/kg 56 mg/kg
Rabbit 1410 mg/kg
Guinea Pig 500 μL/kg 50 μg/24h[7]

Rabbits

In rabbits, perchloromethyl mercaptan was found to be very irritating to the skin and to the eyes.[8][9] When 0.5 mL was utilized to the applied and abraded clipped skin of rabbits under occlusion for 24 hours, and then was washed off, perchloromethyl mercaptan was found to be corrosive, yielding maximum scores for erythema and oedema at all time points.[10] When perchlorometyl mercaptan was applied to the eyes of the rabbits, it was very corrosive and caused complete destruction of the eyes.[8]

After this treatment, three out of the six rabbits died after seven to ten days.

Mice

When cat en mice were exposed to perchloromethyl mercaptan for 15 minutes at 45 ppm, they died within one to two days form pulmonary edema. 50% of the mice died after they were exposed for 3 hours at 9 ppm. Only some mice which were exposed repeatedly over 3 months at 1 ppm died. Exposure that leads to eye irritation began at 1.3 ppm (10 mg/m). When the mice were exposed to a higher concentration, it led to marked irritation of the eyes, throat, and bronchi, as well as nausea.

Rats

Rats were exposed 6 hours a day 5 days a week for two weeks to 0.02, 0.13 or 1.15 ppm. At 0.02 ppm no effects were reported, at 0.13 mild nasal epithelial changes were notified. For 1.15 ppm were mild nasal epithelial changes and pulmonary irritation (labored breathing, increased lung weight, pulmonary edema, increase mucous secretion, alveolitis, intestitial fibroplasia and perivascular edema) were reported. By exposure of 18 ppm for one hour, seven of the ten rats died. When rats (n=7), guinea pigs (n=7) and dogs (n=2) were exposed to 1 ppm (7.7 mg/m) for 8 hours a day, 5 days a week, for 3 months, 6/7 guinea pigs died within 3 weeks while the other animals survived.[6]

Side effects

The side effects of perchloromethyl mercaptan are different according to the concentration and the mode of intake. First the toxic compound causes irritations when in contact with the eyes and skin. Besides irritation, eye exposure may also lead to severe inflammation of the conjunctiva or corneal damage. It can be absorbed through the skin which can cause general toxic effects that are mentioned later. Inhalation of the compound may cause severe irritation to the upper respiratory tract. While ingestion of the liquid can result in mucosal damage, pain and burning of the mouth and throat, nausea, vomiting, cramps and diarrhoea. Furthermore, via all modes of intake, short exposure to low concentrations may result in central nervous system depression, congestion of the lung, liver and heart and tissue ulceration. Even short exposure to very small quantities can have severe effects, including permanent injury or death.[11]

Treatment

What to do when you get in contact with perchloromethyl mercaptan:

Inhalation

In case of inhalation of perchloromethyl mercaptan, you immediately should move to fresh air. Severe respiratory tract irritation, pulmonary edema and fever could occur. When the lungs are injured acutely, ventilation and oxygenation should be practiced. If difficulty breathing or cough develops, the physician should evaluate respiratory tract irritation.[12]

Ingestion

In case of oral uptake, gastrointestinal tract irritation could occur. Nausea, vomiting, abdominal pains, possible mucosal ulceration and diarrhea are common symptoms. When perchloromethyl mercaptan has been ingested, someone immediately should be diluted with 120 to 240 mL of water or milk. Removal of some ingested material can be beneficial, but it should be weighed against potential complications. Bleeding or perforation can occur during this cautious gastric lavage.[13] Most toxic compounds are able to bind activated charcoal. Thereby, the activated charcoal decreases the absorption of the toxic compound. It should be administered soon after ingestion of perchloromethyl mercaptan. 25 to 200 g of activated charcoal should be administered, though the charcoal must be solved in water. Ultimate, an esophagoscopy can be accomplished to determine the extent of injury. This only should be performed in case of significant esophageal irritation.

Eye exposure

When eyes are exposed to perchloromethyl mercaptan, the eyes must be irrigated for at least 15 minutes with lots of room temperature water. Pain, swelling, irritation, lacrimation or photophobia could persist. In that case, you should go to a health care facility to check your eyes.[12]

Skin exposure

When the skin is exposed to perchloromethyl mercaptan, the contaminated clothing should immediately be removed from the body. The area which is exposed must be rinsed with water and soap. Pain and irritation could persist. Like the eye exposure, you should go to a healthy care facility or physician to examine your skin.[14]

References

  1. 1 2 3 "Perchloromethyl mercaptan". Immediately Dangerous to Life and Health. National Institute for Occupational Safety and Health (NIOSH).
  2. 1 2 3 "NIOSH Pocket Guide to Chemical Hazards #0489". National Institute for Occupational Safety and Health (NIOSH).
  3. 1 2 3 4 5 Committee on Acute Exposure Guideline Levels, Committee on Toxicology, National Research Council, (2011), Acute Exposure Guideline Levels for Selected Airborne Chemicals.
  4. 1 2 3 Sosnovxky, G., (1968), The Chemistry of Trichloromethansulfenyl chloride, Institute of Organic Chemistry, Chicago.
  5. 1 2 3 Greco, C., (1978), Production of perchloromethyl mercaptan, Stauffer Chemical Company, Westport, Conn.
  6. 1 2 Health-based Reassessment of Administrative Occupational Exposure Limits Committee on Updating of Occupational Exposure Limits, a committee of the Health Council of the Netherlands.
  7. ↑ Catalog of Chemical Suppliers, Custom Synthesis Companies and Equipment Manufactures.
  8. 1 2 American Conference of Governmental Industrial Hygienists (ACGIH), (2000), Guide to occupational exposure values.
  9. ↑ National Institute for Occupational Safety and Health (NIOSH), (1999), Methanesulfenyl chloride, trichloro, Registry of Toxic Effects of Chemical Substances (RTECS).
  10. ↑ Saylor JF, Bullock CH., (1971), Perchloromethyl mercaptan. Stauffer Chemical Company, Western Research Center.
  11. ↑ http://www.chemicalbook.com/ChemicalProductProperty_EN_CB7209949.htm
  12. 1 2 Rumack B.H, (2012), Poisindex, Information system Micromedex, Vol. 152, Englewood
  13. ↑ http://www.microkat.gr/msdspd90-99/Perchloromethyl%20mercaptan.htm
  14. ↑ Rumack B.H, (2012), Poisindex, Information system Micromedex, Vol. 152, Englewood.

External links

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