Last updated
Preferred IUPAC name
Other names
Thioformaldehyde trimer, Trimethylentrisulfide, Trimethylene trisulfide, Trithioformaldehyde, 1,3,5-Trithiacyclohexane, sym-Trithiane, Thioform, s-Trithiane
3D model (JSmol)
ECHA InfoCard 100.005.482 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 206-029-7
PubChem CID
  • InChI=1S/C3H6S3/c1-4-2-6-3-5-1/h1-3H2 Yes check.svgY
  • InChI=1/C3H6S3/c1-4-2-6-3-5-1/h1-3H2
  • S1CSCSC1
Molar mass 138.27
AppearanceColourless 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
Occupational safety and health (OHS/OSH):
Main hazards
Toxic (T)
GHS labelling:
P264, P280, P305+P351+P338, P313
NFPA 704 (fire diamond)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

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) + RBr → (CH2S)2(CHRS) + LiBr
(CH2S)2(CHRS) + H2O → RCHO + ....

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
Sample of sym-trithiane. SymTrithiane.jpg
Sample of sym-trithiane.


Trithiane is the parent of a class of heterocycles called trithianes, that formally result from substitution of various monovalent groups for one or more of the hydrogen atoms. The species often arise from thiation of ketones and aldehydes. The incipient thioketones and thioaldehydes undergo trimerization. One example is 2,2,4,4,6,6-hexamethyl-1,3,5-trithiane, or trithioacetone, the trimer of thioacetone (propane-2-thione). Alternatively 1,3,5-trithiane can be deprotonated and alkylated to afford (SCH2)n(SCHR)3-n. [5]

The conformation of trithianes has been well investigated. [6]


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  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
  5. Edema, Jilles J. H.; Hoogenraad, Marcel; Schoonbeek, Franck S.; Kellogg, Richard M.; Kooijman, Huub; Spek, Anthony L. (2010). "Alkylation of the SCS linkage. Towards lipophilic mono- and ditopic heavy-metal receptors containing trithiane building blocks. Molecular structure of cis-2,4,6-tribenzyl-1,3,5-trithiane". Recueil des Travaux Chimiques des Pays-Bas. 112 (6): 370–375. doi:10.1002/recl.19931120611.
  6. Breslow, David S.; Skolnik, Herman (2009). "C3S3 Ring Systems". Multi-Sulfur and Sulfur and Oxygen Five- and Six-Membered Heterocycles, Part 2. Vol. 21. p. 689. ISBN   978-0-470-18833-0.