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. It is the trimer of thioformaldehyde.
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.
(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:
(CH2S)3 + 9 Cl2 + 6 H2O → 3 ClCH2SO2Cl + 12 HCl

Chemical Name	1,3,5-trithiane
Synonyms	Trithiometaformaldehyde;1,3,5-trithian;sym-Trithian;1,3,5-Trithiane;[1,3,5]trithiane;Thioform [Czech];Thioformaldehyde trimer;s-Trithiane;Trithioformaldehyde;Thioform;sym-Trithiane;1,3,5-trithiacyclohexane;Trimethylene trisulfide;Collapse
CAS No.	291-21-4
Molecular Formula	C3H6S3
Molecular Weight	138.27500
PSA	75.90000
LogP	2.07210

EINECS number	206-029-7
MDL number	MFCD00006653

Appearance & Physical State	white to off-white crystalline powder
Density	1.318g/cm3
Boiling Point	230.7ºC at 760mmHg
Melting Point	215-220ºC
Refractive Index	1.651
Vapor Pressure	0.0983mmHg at 25°C

RTECS	YL8225000
Safety Statements	S22-S24/25
HS Code	2934999090
WGK Germany	3