2,3,4,5-Tetrahydrothiophene stands as a unique sulfur-containing compound with a five-membered saturated ring. The structure features a thiophene core, but in this variant, all the double bonds have given way to single bonds, making it a fully hydrogenated form. People call it by the CAS number 6390-80-5, and on the market, you might see it presented as solid flakes, clear liquid, or even as a crystalline powder, depending on the specific production route and temperature. On paper, the molecular formula reads C4H8S, shaping a ring with four carbon atoms and one sulfur atom. The material brings a fairly strong, distinctive, sometimes foul odor, which isn’t surprising for sulfur heterocycles. Many chemical suppliers list this material under the HS Code 2934999099 when moving it across borders.
Getting close to 2,3,4,5-tetrahydrothiophene in a lab, it’s easy to appreciate its chemical stubbornness and characteristic smell that lingers. The compound carries a molecular weight of 88.17 g/mol. At room temperature, it often appears as a colorless to light yellow liquid, but under colder storage conditions, it tends toward crystalline flakes or fine solid powder. Its melting point sits near -4°C, and it boils somewhere around 129°C. The material’s density rests at about 0.98 g/cm³, whether in liquid or solid state, and dissolves only sparingly in water—more at ease in organic solvents like ethanol or ether. In terms of behavior, this compound stays stable under standard lab conditions, but shows reactivity when strong oxidizers get involved or under intense heat.
Holding a bottle of 2,3,4,5-tetrahydrothiophene, what stands out is the simple ring with sulfur forming part of the backbone. The ring doesn’t carry any external functional groups, so most reactions target the sulfur atom or focus on ring-opening transformations. Chemists have adopted it for years as a reference molecule and synthetic building block. The formula C4H8S reflects a saturated five-membered ring with a sulfur atom sitting at the 1-position. The different forms—whether flakes, crystalline, or as a viscous liquid—depend strongly on storage and handling. You might find it as pearls or as a dense liquid, and it readily transitions between forms as temperatures shift.
Industry has found ways to use 2,3,4,5-tetrahydrothiophene as a raw material or intermediate for more complex molecules, such as in pharmaceuticals, rubber additives, and certain high-performance polymers. Its reactivity profile makes it helpful as a starting point for compounds where sulfur presence matters. In solution, whether water-based or organic solvent, it keeps most of its original odor and remains quite potent. As a material, the density hovers close to that of water, and the physical state can prove tricky—handling as a solid powder avoids spills, while the liquid form can spread its aroma far and wide. Despite being considered relatively stable away from strong acids and bases, 2,3,4,5-tetrahydrothiophene falls under hazardous chemical regulations in many jurisdictions, requiring controlled handling, ventilation, and personal protective equipment, mostly due to its volatility and strong odor.
Working with 2,3,4,5-tetrahydrothiophene means respecting its health hazards. Inhalation or direct skin contact can cause irritation. Long exposure in poorly ventilated areas may even bring headaches or dizziness. For that reason, chemists keep it behind fume hoods, storing bulk material in air-tight, labeled containers. The chemical doesn’t rate as carcinogenic, but its acute toxicity and noxious smell make it less than ideal for open workspaces. Cleanup after a spill involves absorbent material, sealed waste, and proper disposal as a hazardous substance. Disposal always follows environmental regulations to prevent sulfur pollution in soil or waterways.
Suppliers package 2,3,4,5-tetrahydrothiophene in weight-measured flasks or drums—some provide it as liters of solution in dip tubes for safer transfer. Purity sits between 95% and 99%, and datasheets report typical densities, melting and boiling points, along with hazardous codes for each packaging size. Shipments list it under HS Code 2934999099 or related trade codes, and buyers demand certificates of analysis detailing batch-to-batch specifications, including information about any stabilizers and impurity levels. The broad range of forms—solid, powder, liquid, or crystal—has roots in transportation, climate conditions, and intended field of use.
Many chemists agree: keeping odorants and sulfur compounds like this one happy means tight containment and good habits. Simple fixes—like sealed vessels, spill trays, and labeled storage—cut down on accidental releases. Workshops and labs that value safety invest in extraction fans and chemical sensors for accidental leaks. Making the workplace a bit friendlier for both people and the environment often depends on how strictly those handling rules get followed. Investing up front in real-world safety—rather than just relying on paperwork and warning labels—usually costs less than dealing with a major spill or exposure event.
