IUPAC name
Other names
Thioformaldehyde trimer, Trimethylentrisulfide, Trimethylene trisulfide, Trithioformaldehyde, 1,3,5-Trithiacyclohexane, sym-Trithiane, Thioform, s-Trithiane
291-21-4 N
3D model (Jmol) Interactive image
ChEBI CHEBI:39196 YesY
ChemSpider 8907 YesY
ECHA InfoCard 100.005.482
EC Number 206-029-7
PubChem 9264
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
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