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IUPAC name
Other names
Thioformaldehyde trimer, Trimethylentrisulfide, Trimethylene trisulfide, Trithioformaldehyde, 1,3,5-Trithiacyclohexane, sym-Trithiane, Thioform, s-Trithiane
3D model (Jmol)
ECHA InfoCard 100.005.482
EC Number 206-029-7
Molar mass 138.27
Appearance Colourless solid
Density 1.6374 g/cm3[1]
Melting point 215 to 220 °C (419 to 428 °F; 488 to 493 K)
Slightly soluble
Solubility Benzene
Main hazards Toxic (T)
S-phrases S22, S24/25
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

1,3,5-Trithiane is the chemical compound with the formula (CH2S)3. This heterocycle is the cyclic trimer of the otherwise unstable species thioformaldehyde. It consists of a six-membered ring with alternating methylene bridges and thioether groups. It is prepared by treatment of formaldehyde with hydrogen sulfide.[2]

Trithiane is a building block molecule in organic synthesis, being a masked source of formaldehyde. In one application, it is deprotonated with organolithium reagents to give the lithium derivative, which can be alkylated.[3]

(CH2S)3 + RLi → (CH2S)2(CHLiS) + RH
(CH2S)2(CHLiS) + R’Br → (CH2S)2(CHR’S) + LiBr
(CH2S)2(CHR’S) + H2O → R’CHO + ….

Trithiane is the dithioacetal of formaldehyde. Other dithioacetals undergo similar reactions to the above.

It is also a precursor to other organosulfur reagents. For example, chlorination in the presence of water affords the chloromethyl sulfonyl chloride:[4]

(CH2S)3 + 9 Cl2 + 6 H2O → 3 ClCH2SO2Cl + 12 HCl


Trithiane is the parent of a class of heterocycles called trithianes. The species often arise from thiation of ketones and aldehydes. The incipient thioketones and thioaldehydes suffer trimerization. The reaction is reversed thermally.



  1. ^ David R. Lide, ed. Handbook of Chemistry and Physics, 85th Edition, Internet Version 2005. CRC Press, 2005.
  2. ^ Bost, R. W.; Constable, E. W. "sym-Trithiane" Organic Syntheses, Collected Volume 2, p.610 (1943). http://orgsyn.org/Content/pdfs/procedures/CV2P0610.pdf
  3. ^ Seebach, D.; Beck, A. K. “Aldehydes From sym-Ttrithiane: n-Pentadecanal” Organic Syntheses, Collected Volume 6, p.869 (1988). http://orgsyn.org/Content/pdfs/procedures/CV6P0869.pdf
  4. ^ Paquette, L. A.; Wittenbrook, L. S. “2-Chlorothiirane 1,1-Dioxide” Organic Syntheses, Collected Volume 5, p.231 (1973). http://orgsyn.org/Content/pdfs/procedures/CV5P0231.pdf