Chemists have explored thiophene derivatives for over a century, and 2-Chloro-3-Methylthiophene developed a reputation on its own as early aromatic heterocycles took center stage in the search for new pharmaceuticals and materials. As synthetic organic chemistry grew more precise in the late 20th century, laboratories recognized that selective chlorination and methylation of thiophenes could create powerful building blocks. Researchers, especially after 1970, cataloged new methods of functionalization, with prominent journals detailing novel halogenated thiophenes all through the eighties and nineties. In my journey through stacks of chemical literature in graduate school, it became clear that the wider thiophene family owed its breakthroughs to curiosity about sulfur’s role in aromatic reactivity—2-Chloro-3-Methylthiophene featured in many papers as a promising intermediate.
2-Chloro-3-Methylthiophene sits at the intersection of fine organic synthesis and industrial demand. Produced and sold as a specialty chemical, this compound acts as an intermediate in agrochemical and pharmaceutical synthesis. Companies ship it in sealed amber glass for lab-scale orders, with larger quantities handled in drums outfitted for hazardous goods. The compound’s role as both a starting material and a diagnostic probe in heterocyclic chemistry gives it a solid place in research catalogs. In my own lab, requests for this compound often came from teams developing anti-infective leads or scouting new materials for organic electronics.
This molecule presents as a colorless to pale yellow liquid with a sharp, sulfur-like odor—reminding anyone uncapping it that they’re handling a thiophene derivative. Its boiling point clusters around 148 to 150°C, according to technical databooks. Solubility sits low in water, but ethanol, ether, and other organic solvents work fine. Reactivity flows from its electron-rich aromatic ring plus the activation given by the methyl substituent—with the chlorine atom creating easy entry for cross-coupling chemistry. Stability under ambient conditions is decent, though exposure to strong base or oxidizers pushes the molecule to break down or react.
Packaged with precise labeling regulations, bottles of 2-Chloro-3-Methylthiophene bear chemical identifiers including CAS number 17249-11-3, purity percentages (often above 98%), batch tracking, and hazardous substance pictograms. Safety datasheets come attached, detailing recommended storage temperatures (usually cool, dark, and dry), avoidance of ignition sources, and the need for well-sealed containers. Many suppliers validate the product via GC-MS or NMR trace, giving a spectrum or chromatogram reference to reassure labs of purity. Years in chemical supply taught me that plenty of headaches stem from poorly labeled batches, especially under rushed research timelines, so getting specifications right matters.
Production often starts with 3-Methylthiophene, which undergoes selective electrophilic chlorination. Commonly, reagents like sulfuryl chloride or N-chlorosuccinimide serve for introducing the chlorine atom. The process tends to run in polar aprotic solvents, sometimes at sub-ambient temperatures to avoid poly-chlorination or ring degradation. Recovery includes fractional distillation under reduced pressure to isolate the target isomer. Every synthesis run demands close monitoring by TLC or GC to catch side products and incomplete reactions. In the push to reduce costs, some plants scale up with continuous flow reactors, aiming for steadier conversions and safer containment of chlorine byproducts.
Chemists value 2-Chloro-3-Methylthiophene for how smoothly it accepts substitution at the 2-chloro position. Palladium-catalyzed cross-coupling reactions, like Suzuki and Stille, pave the way for new carbon bonds—key steps in building complex heterocycles, ligands, or bioactive molecules. Nucleophilic aromatic substitution with amines or alkoxides results in tailored derivatives, sharpening the molecule’s utility further. Halogen-metal exchange, using organolithium or Grignard techniques, gives another path for crafting alcohols or carboxylic acids on the ring. In my hands, small shifts in reaction temperature had outsize impact on yields and selectivity, so chemists working on scale-up keep a close eye on each degree.
The chemical world has a way of multiplying names. Researchers and suppliers list this compound as 2-Chlor-3-methyl-thiophene, or 2-Chloro-3-Methylthiofuran, and sometimes as 3-Methyl-2-chlorothiophene. In trade and patents, quick labels like CMT or CMThiophene crop up. Anyone searching for literature or regulatory data learns quickly to scan for all variants, especially when navigating international databases or customs paperwork. CAS numbers (like 17249-11-3) help cut through much of that confusion.
Standard hazard pictograms for 2-Chloro-3-Methylthiophene highlight flammability and acute toxicity, with heavy emphasis on ventilation and engineering controls for industrial settings. Spills risk environmental release, so containment and personal protective gear matter daily in the plant. Respirators, nitrile gloves, and safety goggles feature whenever open handling happens. Legal regulations in the EU and US mandate reporting by companies who import or manufacture volumes above set limits, triggering waste disposal and environmental monitoring protocols. During my times at the bench, treating even trace amounts with respect went a long way to preventing incidents and keeping audits clean.
Companies in the agrochemical sector use this compound as an intermediate on routes to new pesticides and growth regulators. Pharmaceutical groups treat it as a scaffold for antimalarial, antifungal, and antiviral drug candidates—the thiophene ring sometimes enables activity against tricky targets. Material scientists incorporate it into research on organic semiconductors, where minute tweaks to ring substitution change charge mobility and performance in flexible electronics. During tech transfer assignments, I saw the molecule’s reach extend across continents, with startup and blue-chip firms alike chasing subtle benefits from precise chemical modifications.
Active development focuses on greener synthesis routes and adaptation for automated chemistry platforms. The move to less hazardous chlorinating agents and recyclable solvents reflects both new regulations and project economics. Digital labs catalog reactivity profiles and optimize process windows with machine learning models—cutting both waste and cycle times. Researchers publish procedures that cut isolation steps or reduce purification costs, and this level of incremental improvement often drives adoption in cost-conscious pharmaceutical research. In my last job, collaborations between universities and manufacturers advanced flow chemistry hardware for better containment and reproducibility, which has started to ripple through procurement choices.
Animal studies indicate moderate acute toxicity, with LD50 values in the hundreds of milligrams per kilogram for mice by oral administration. Repeated exposure raises liver enzyme levels in test models, indicating potential cytotoxic effects on metabolic organs. Little evidence shows chronic carcinogenicity at tested doses, but lack of full long-term studies keeps regulatory bodies cautious. Inhalation of vapor or accidental skin contact can cause irritation, adding to the risk for industrial workers outside lab settings. My discussions with occupational safety experts confirm the focus on engineering controls and monitoring to protect both handlers and the environment from cumulative exposure.
Expect research to dig deeper into bioactivity screens, especially as combinatorial libraries expand the ways thiophene derivatives target infection or inflammation. Automation and data-driven synthesis may bring cleaner, cheaper routes, opening access for smaller research outfits or new geographic regions. Recyclable packaging and energy-efficient reactors could lessen the environmental burden from manufacturing. As electronic materials research matures, 2-Chloro-3-Methylthiophene’s aromatic scaffold might become key for next-generation flexible displays or sensors. New regulatory guidelines and end-of-life chemical handling procedures could change as governments set tighter thresholds for aromatic halides, pushing both industry and academia toward safer alternatives or upgraded containment.
