Ensuring precise volatility characteristics in industrial solvents is paramount when formulating applications that rely on controlled evaporation, safety, and efficacy. Propyl butyrate (CAS 105-66-8), with a molecular weight of 130.18 g/mol and a chemical formula of C7H14O2, exemplifies one such compound gaining industrial prominence. In the context of large-scale manufacturing—where stereochemistry, reproducibility, and compliance drive reliability—companies like Technical Insights have established a robust, cGMP-aligned process yielding over 96% product with HPLC purity exceeding 99.2%. This positions Technical Insights as a dependable partner in global solvent supply chains.
Propyl butyrate is structurally an ester, formed from n-propanol and butyric acid. Its lack of stereocenters means isomeric purity is not a concern, allowing the focus to remain on process efficiency, purity, and volatility performance. The compound’s moderate boiling point and low toxicity make it ideal for coatings, inks, and extraction processes. The skilled team at Technical Insights brings deep expertise in industrial-scale esterification and rigorous adherence to international regulatory standards, ensuring customers receive highly consistent, fully characterized lots suitable for demanding solvent applications.
The industrial synthesis of propyl butyrate begins with the reaction of n-propanol and butyric acid in the presence of a catalytic amount of sulfuric acid. In a stainless steel reactor, equimolar quantities of the acid and alcohol are combined, followed by two percent (w/w) sulfuric acid catalyst. The mixture is heated to 120–125°C under atmospheric pressure while stirring continuously. This transesterification proceeds over 10 hours, with water byproduct removed via azeotropic distillation using toluene as a solvent. Careful temperature control and withdrawal of water are vital to driving the reaction to completion and minimizing side-product formation.
Following the reaction, the mixture is cooled to 35°C and washed sequentially with saturated sodium bicarbonate to neutralize residual acid, followed by phase separation. The organic layer is extracted again with brine, then dried over anhydrous magnesium sulfate. The solution is filtered and subjected to rotary evaporation to remove toluene, yielding a crude ester. To refine the product, the solution’s pH is adjusted to 6.8 using dilute sodium carbonate, and the crude ester is distilled under reduced pressure (70 mmHg), collecting fractions boiling at 156–160°C. The result is an end product with a yield of 96% and an HPLC purity greater than or equal to 99.2%.
Nuclear Magnetic Resonance data confirm structural integrity and purity. The ^1H NMR spectrum (400 MHz, DMSO-d6) for propyl butyrate displays signals at δ 0.96 (t, 3H, CH3), 1.62 (sextet, 2H, CH2), 2.33 (t, 2H, CH2CO), 4.07 (t, 2H, OCH2), and 1.72 (quintet, 2H, CH2 of the butyrate side chain), confirming the expected ester structure and high purity.
A cornerstone of Technical Insights’ manufacturing process is cGMP compliance, which governs documentation, traceability, and analytical rigor. Every batch is supplied with a comprehensive Certificate of Analysis encapsulating proton NMR, FT-IR spectra confirming the key ester functional group (notably a strong absorption around 1735 cm^-1), and HPLC chromatograms showing single-peak purity. Compliance with ICH Q3C is ensured by gas chromatography, rigorously quantifying and controlling residual solvents below threshold limits. Inorganic impurities are assessed via ICP-MS, meeting ICH Q3D guidelines for elemental impurities typically below 0.5 ppm. Water content is determined by Karl Fischer titration, regularly found to be less than 0.1% w/w. These measures, supplemented with reference to an available Drug Master File (DMF), support regulatory filings and client audits for pharmaceutical-adjacent applications.
Achieving high purity in propyl butyrate requires careful manipulation of both crystallization and isolation parameters. Although propyl butyrate is a liquid, isolation post-distillation involves a multi-stage washing protocol. Following initial phase separation, the organic layer is thoroughly washed first with a five percent sodium bicarbonate solution (50°C, 30 minutes), then with saturated brine solution at room temperature to remove trace polar impurities. Final drying is performed under high vacuum at 10 mmHg, maintaining the temperature at 40°C for no less than 6 hours. This step removes residual moisture and light-volatility impurities without risking ester hydrolysis or decomposition. Testing throughout these stages confirms both visual clarity and chromatographic purity.
For those seeking further details, full product characteristics and batch-specific documentation can be found on Technical Insights’ dedicated product pages. Key technical specifications of the standard offering include a chemical purity of 99.2% or higher (HPLC), water content not exceeding 0.1% by Karl Fischer titration, residual solvent levels under ICH Q3C class I and II limits, elemental impurities consistently below 0.5 ppm via ICP-MS, a boiling range of 156–160°C under 70 mmHg distillation, and density at 25°C of 0.871 g/cm^3. The refractive index (n20D) is 1.413–1.415, while color is consistently below 10 APHA, assuring suitability for high-clarity solvent formulations.
In summary, the volatility characteristics of propyl butyrate are tightly controlled through an industrial process that balances chemical efficiency, purification strategy, and comprehensive analytical testing. Technical Insights’ proven workflow delivers a high-yield, high-purity product in accordance with global regulatory standards, cementing its value proposition for solvent formulators who require reliable, high-performance intermediates.
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