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IUPAC name 1,3,5-Trithiane
Other names Thioformaldehyde trimer, Trimethylentrisulfide, Trimethylene trisulfide, Trithioformaldehyde, 1,3,5-Trithiacyclohexane, sym-Trithiane, Thioform, s-Trithiane
CAS number 291-21-4
PubChem 9264
EINECS number 206-029-7
Molecular formula C3H6S3
Molar mass 138.27
Appearance Colourless solid
Density 1.6374 g/cm3[1]
Melting point

215-220 °C

Solubility in water Slightly soluble
Solubility Benzene
Main hazards Toxic (T)
NFPA 704

NFPA 704.svg

S-phrases S22, S24/25
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and 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 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 in turn 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 chloromethylsulfonyl chloride:[4]

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


  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://www.orgsyn.org/orgsyn/pdfs/CV2P0610.pdf
  3. Seebach, D.; Beck, A. K. “Aldehydes From sym-Ttrithiane: n-Pentadecanal” Organic Syntheses, Collected Volume 6, p.869 (1988). http://www.orgsyn.org/orgsyn/pdfs/CV6P0869.pdf
  4. Paquette, L. A.; Wittenbrook, L. S. “2-Chlorothiirane 1,1-Dioxide” Organic Syntheses, Collected Volume 5, p.231 (1973). http://www.orgsyn.org/orgsyn/pdfs/CV5P0231.pdf