Methyl 4-Chlorobutyrate stands as a useful specialty chemical for those in synthesis-focused fields. It goes by the molecular formula C5H9ClO2, which spells out five carbons, nine hydrogens, one chlorine, and two oxygens. The structure consists of a methyl ester attached to a four-carbon butyrate chain, out of which the chlorine atom sits on the fourth carbon. This configuration opens up many doors for targeted organic transformations and intermediate processes. In my own time working with chemical intermediates, handling this compound gives you a sense that, while it appears deceptively simple, it often plays an outsized role in more advanced synthesis. I’ve seen it used for pharmaceutical intermediates, agrochemical building blocks, and specialty performance materials. Across these fields, accuracy in composition and a clear understanding of molecular layout matter. From a practical laboratory perspective, its structural framework permits diverse modifications, especially useful for custom synthesis and fine chemical development.
In the lab and warehouse, Methyl 4-Chlorobutyrate most often flows as a colorless to pale yellow liquid. It releases a characteristic, almost fruity odor, which hints at its ester group. The density hovers around 1.1 to 1.12 g/cm³ at standard temperature, according to verified references such as Merck and Sigma-Aldrich. Every time I’ve measured it, samples have poured clearly, neither flaked nor crystallized at room temperature. Since its melting point sits at about -30°C, and its boiling point stretches up near 210°C, it rarely solidifies under common storage. While this chemical doesn’t come in powder, crystal, or solid beads, some producers supply it in bulk liters or tightly capped glass bottles. Each approach demands proper labeling to prevent accidents. For safe material handling, I follow the Safety Data Sheets, which confirm that improper contact or inhalation can cause irritation. You won’t find this product as flakes, pearls, or powder on the regular market—it's always liquid—so storage must focus on spill prevention and ventilation. Density checks play a big role in verifying quality batches, especially when purity standards come into play for regulated applications.
At a molecular level, Methyl 4-Chlorobutyrate enters with a molar mass of about 136.58 g/mol. Its structure gives it polar characteristics because of the carbonyl and chlorine groups, which means it mixes well with certain organic solvents like ether or ethyl acetate, and less so with water. In practice, this trait often determines its use as an intermediate—many reactions count on it to dissolve swiftly and interact with nucleophiles. One run-in with a batch that failed a purity check (less than 98%) threw a whole kinetic analysis off, proving how crucial precise specifications remain. Purities typically start at 98% for reagent grades. A key analytical test like gas chromatography can confirm purity levels, and specific refractive index readings (about 1.430-1.440 at 20°C) set benchmarks for acceptance in chemical inventories. Each property connects to downstream results in synthesis, and discrepancies invite batch failures.
Looking at the regulatory side, the Harmonized System (HS) Code for Methyl 4-Chlorobutyrate, which tracks international trade, usually registers as 2915.90. When ordering or exporting, this code cuts through border confusion and lines up customs paperwork. For industrial importers, knowing the right code saves both time and money on taxes and compliance. From a safety angle, the chemical has hazards that cannot go ignored. It counts as both harmful and hazardous—inhaling vapors may irritate the respiratory system, skin or eye splashes prompt burning, and long exposure calls for gloves, goggles, and lab coats. Storage guidelines restrict it to cool, well-ventilated spots, kept clear of open flames or reactive bases. In my lab, once a minor spill went unnoticed on a benchtop and within twenty minutes left a surprising trail of pungent odor and sticky residue. Such episodes reinforce why all bottles carry hazard pictograms and why neutralizing spills with absorbent pads stands as a basic safety must. Laboratories and warehouses must also be ready for fire risk, as vapors can ignite at higher concentrations.
Almost nobody produces Methyl 4-Chlorobutyrate for use by itself; most of its life gets spent as a raw material for other chemicals. It offers a key intermediate for esterification, alkylation, and reductive amination reactions, all pivotal in advancing pharmaceutical APIs or agrochemical agents. Each time medicinal chemists tweak chain lengths or swap out functional groups to adjust biological profiles, access to a reliably pure chlorinated butyrate speeds things up. Some automotive or electronics manufacturers also incorporate it during the crafting of specialty polymers, counting on the ester to help set needed material flexibilities. So far, the greatest value comes from its ability to link to a broad menu of nucleophiles, which supports countless lab-scale pilot reactions for bigger product campaigns.
Managing Methyl 4-Chlorobutyrate means paying attention to every transfer and every seal. Always use in fume hoods, with chemical-resistant gloves and splash-proof eyewear, regardless of the job’s size. Training the staff to read Material Safety Data Sheets remains non-negotiable. Long-term storage calls for cool, shaded areas, far from incompatible acids or oxidizing reagents. Glass or HDPE containers with solid vinyl seals work best. I still recall a near-miss in a shared storage room when a forgotten bottle reacted with spilled cleaning agents, producing a stubborn residue and a costly clean-up. Proper waste disposal also avoids fines and health scares: collect any leftover solutions for certified incineration, not ordinary sinks or trash bins.
Disposal and emissions top the list of environmental issues. Methyl 4-Chlorobutyrate, while not the most notorious pollutant, still brings concerns because esters hydrolyze in nature, and the resulting byproducts may persist. Regulations in most countries require secondary containment, air emission controls, and careful waste separation to avoid accidental release. Adhering to local EPA standards, as well as REACH and TSCA listings, has become routine for any serious producer or user. Responsible sourcing and recycling cut down overall chemical footprints, with suppliers now facing more scrutiny for every kilogram shipped across borders. When chemistry teams recycle volatile organics, both costs and emissions shrink, adding further reasons to monitor every step from purchase order to disposal manifest.
Behind every bottle or barrel, product labeling repeats the keyword details: name, formula (C5H9ClO2), batch number, hazard class, and HS Code. For shipment, triple-layered packaging makes the difference between an uneventful delivery and an emergency stop at customs. Clear hazard symbols, safety phrases, and emergency contacts appear on every drum or carton sent by reputable suppliers. In my experience, poor labeling brings delays—border agents have no tolerance for missing UN numbers or ambiguous language. So, on the buying side, I always ask for lab analysis certification and independent quality controls before accepting delivery. These habits keep both companies and end-users safe, compliant, and ready to support audit requests at any time.
