Few chemicals catch the eye in a laboratory quite like 5,6,7,7a-Tetrahydrothieno[3,2-c]pyridin-2(4H)-one hydrochloride. This compound doesn’t just come in one physical form. I’ve come across it as a white to off-white solid, often in flakes or powder. Sometimes it turns up as small crystalline pearls, but rarely as a liquid under standard conditions. It belongs to the thienopyridine family, carrying the molecular formula C7H10ClNOS. The hydrochloride salt brings greater stability, making handling easier in most environments outside specialized facilities.
Exploring the structure reveals a bicyclic backbone: a thienopyridinone core supplemented by saturated positions that tweak its reactivity and solubility. The hydrochloride level affects both the melting point and its moisture uptake. Based on the structure, government authorities usually assign the HS Code 2934999099, placing it among "other heterocyclic compounds" for customs and regulatory tracking. The molecule mixes aromatic and saturated elements, creating unique properties and influencing its performance in target reactions or synthesis protocols. Each hydrochloride salt structure features a chloride ion locked in the crystal lattice—giving extra mass and a greater melting point than the base free compound.
I’ve found this material stable under dry conditions but hygroscopic, eager to absorb water from open air. Density comes in around 1.30–1.36 g/cm³ for the solid, with specific values depending on how tightly it's packed—always best to store sealed with desiccants when possible. The melting point tends to sit above 200°C. If you handle it as a solution, solubility in water generally stays high, thanks to hydrochloride’s ionic character, while alcohols and DMSO also bring it to full dissolution. Crystal forms matter during storage. Clumping into larger, glassy chunks happens if it's left open, which slows down weighing or mixing in the lab. In my own cataloguing, flakes and free-flowing powders work best for routine synthesis since they resist clumping and require less grinding or measurement correction.
Like most small-molecule heterocyclic chemicals, this one brings safety considerations to every bench. The hydrochloride form doesn’t turn volatile, but dust may become an inhalation concern in poorly ventilated spaces. This chemical earns a spot on hazardous material inventories: it may irritate skin, and respiratory tract exposure can cause mild discomfort. Long sleeves, gloves, and goggles go from nice-to-have to must-have during transfer or weighing. Chemical supply labels also mark it as potentially harmful, especially in large quantities or extended contact—MSDS sheets recommend careful disposal, keeping waste away from drains, and handling spills with absorbent material rather than water. Since it doesn’t tend to vaporize, the greatest risks revolve around accidental ingestion or skin absorption. Labs working with it should keep vapor scrubbing gear handy, although spills rarely escalate beyond basic chemical cleanup.
The backbone of 5,6,7,7a-tetrahydrothieno[3,2-c]pyridin-2(4H)-one hydrochloride fits snugly into advanced pharmaceutical development and fine organic synthesis. As a raw material, its saturated heterocycle sets the stage for diverse transformations—everything from enzyme inhibitors to building blocks for custom ligands. Due to its stable crystalline nature, storage and inventory management rarely become complex so long as moisture control stays a priority. This same physical reliability explains why supply chains prefer the hydrochloride rather than the free base. Multiple research teams keep it on the bench as a standard for combinatorial chemistry, but it pops up in specialty agrochemical projects, too, where the sulfur atom in the thienopyridinone ring delivers unique biological properties. Knowing what reaction conditions suit this material—whether heating cycles, pH swings, or light sensitivity—frequently saves both time and resources during synthesis runs.
In the logistics chain, solid and powdered forms offer longevity where temperature swings or transit delays might challenge restricted liquid reagents. Proper containers, silica gel packets, and clear hazard labeling matter more here than any paperwork—since a slight oversight can turn flakes into a sticky, useless mess or cause a preventable laboratory accident. On the specification side, top-tier suppliers provide certificates of analysis to confirm the molecular weight, precise melting point, chloride content, and lack of heavy metal or organic contaminants. Each batch often includes an IR or H-NMR spectrum, reassuring buyers about authenticity before use in synthesis. Tracking density and hydration means nothing gets left to chance. As regulations change and new safety studies surface, product labeling and hazard handling routines may shift, but thorough familiarity with the material pays off more than regulatory compliance books ever could. In my experience, even small improvements—better weighing methods, fresh desiccant, a new container—translate directly into fewer headaches and safer, more productive work at every step.
