Key Property Q&A What is the propionic anhydride structure? Propionic anhydride has the structure (CH₃CH₂CO)₂O - two propionyl groups (CH₃CH₂C=O) connected through a bridging oxygen atom, forming a symmetric acid anhydride.  |  Is propionic anhydride the same as propanoic anhydride? Yes - propionic anhydride and propanoic anhydride are identical compounds; propionic acid is the common name for propanoic acid.  |  What happens when propionic anhydride reacts with water? It hydrolyzes to give two molecules of propionic acid: (CH₃CH₂CO)₂O + H₂O → 2 CH₃CH₂COOH. This is why it must be stored dry and away from moisture.  |  How does propionic anhydride compare to acetic anhydride? Both are acylating agents, but propionic anhydride introduces a three-carbon propionyl chain vs. acetic anhydride's two-carbon acetyl group, giving products higher lipophilicity. Propionic anhydride is generally slightly less reactive but more selective for certain substrates.

Specification Item	Industrial Grade Agrochemical / Polymer / Flavor	Pharmaceutical Grade API Synthesis / GMP
Appearance	Colorless transparent liquid, no visible impurities	Colorless transparent liquid, no suspended matter
Purity (GC)	≥ 99.0%	≥ 99.5%
Water Content	≤ 0.1%	≤ 0.05%
Color (Pt-Co)	≤ 10	≤ 5
Boiling Point	167–169 °C	167.5–168.5 °C
Specific Gravity (20 °C)	1.015–1.019 g/cm³	1.016–1.018 g/cm³
Refractive Index (20 °C)	1.403–1.405	1.4035–1.4045
Storage Stability	12 months (sealed, cool <30°C)	18 months (sealed, 5–25°C, dark)
Packaging	200 kg steel drum 1000 kg IBC tote Tank truck	200 kg sealed steel drum IBC tote (N₂-blanketed)

1. Pharmaceutical Industry - API Synthesis & Drug Intermediates

Propionic anhydride is a core acylating agent in pharmaceutical manufacturing. Its most prominent application is in the synthesis of propionic acid-derived NSAIDs: it is a key intermediate in the manufacture of Ibuprofen, Naproxen, and Ketoprofen, where it efficiently introduces the propionyl group under mild, controllable conditions with high yield and minimal side reactions. It is also used in the synthesis of anti-epileptic drugs, antihistamines, and antibiotic intermediates.

Pharmaceutical-grade propionic anhydride (≥99.5%) meets GMP and ICH Q3C residual solvent guidelines, ensuring that the final drug substance complies with Ph Eur, USP, and BP pharmacopoeia standards. By-product propionic acid is non-toxic and easily removed by washing or distillation, simplifying downstream purification.

Reference: PubChem - Propionic Anhydride (NIH) ↗

2. Agrochemical Industry - Herbicides, Fungicides & Growth Regulators

In the agrochemical sector, propionic anhydride is critical for manufacturing propionamide-based pesticides, herbicides, and fungicides. It is used to acylate amine intermediates in herbicide synthesis, improving the biological activity and environmental selectivity of the final active ingredient. It also serves in the synthesis of plant growth regulators (PGRs), improving crop yield and post-harvest stability.

Its high reactivity and clean by-product profile (propionic acid only) make it the preferred acylating agent over propionyl chloride for large-scale agrochemical synthesis, reducing corrosion and waste treatment costs.

3. Flavor & Fragrance Industry - Propionate Esters & Lactones

Propionic anhydride is widely used in the flavor industry to synthesize propionate esters - including methyl propionate, ethyl propionate, and other fruit/creamy esters - and lactones that contribute fruity, buttery, and sweet aroma notes to food, beverages, and cosmetics. As an acylating catalyst and esterification agent, it enhances the yield and purity of propionate flavor chemicals while meeting FCC (Food Chemicals Codex) and FAO/WHO standards for food-contact applications.

4. Cellulose & Polymer Industry - Cellulose Acetate Propionate (CAP)

One of the most significant industrial uses of propionic anhydride is the production of cellulose acetate propionate (CAP), a high-performance thermoplastic polymer. In CAP synthesis, propionic anhydride reacts with cellulose alongside acetic anhydride to introduce both acetyl and propionyl substituents, yielding a polymer with excellent optical transparency, impact resistance, and UV stability. CAP is widely used in optical films, automotive interior coatings, inkjet coatings, and specialty packaging.

Propionic anhydride also modifies other polymers (polyvinyl alcohol, starch) to improve hydrophobicity, heat resistance, and processability - expanding its role in specialty coatings and biodegradable materials.

5. Other Industrial Applications - Dyes, Rubber & Surface Treatment

Propionic anhydride acts as an intermediate and solvent in the synthesis of dyes, pigments, and rubber chemicals, where its acylation capacity enables precise molecular modification of chromophores and cross-linking agents. In metal surface treatment and electroplating, it improves coating adhesion through propionylation of surface hydroxyl groups.

It is also used as a reaction medium and intermediate in the production of specialty lubricant additives and in the propionic anhydride synthesis of fine chemical building blocks used across the specialty chemicals sector.

⚠️ SAFETY NOTE: Propionic anhydride is a corrosive and combustible liquid (flash point 63°C). It hydrolyzes on contact with water to produce corrosive propionic acid. Vapors are irritating to the eyes and respiratory tract. Use only in well-ventilated areas with full PPE.

Bulk pricing tips: Orders above 20 MT (full container load) typically reduce unit cost by 10–15%. Tank truck delivery vs. drum packaging reduces transport cost per ton by 8–12%. Long-term supply agreements (12+ months) offer price stability linked to propionic acid feedstock index, protecting buyers from market volatility. Request a propionic anhydride price quote →

Q: What is the CAS number for propionic anhydride?

The CAS number for propionic anhydride (propanoic anhydride) is 123-62-6. It is also registered as CAS 123-62-6 under its IUPAC name propanoic anhydride and synonyms including propionic acid anhydride and dipropanoyl oxide. This CAS number applies to the pure compound (CH₃CH₂CO)₂O and should be specified in all procurement and customs documentation.

Q: What is the difference between propionic anhydride and acetic anhydride?

Both are organic acid anhydrides and acylating agents, but they differ in the group they introduce: acetic anhydride introduces a 2-carbon acetyl group (CH₃CO–), while propionic anhydride introduces a 3-carbon propionyl group (CH₃CH₂CO–). The extra carbon in propionyl products increases lipophilicity, which is important in pharmaceutical design (improved membrane permeability) and flavor chemistry (different aroma profiles). Acetic anhydride is more reactive and lower cost; propionic anhydride is preferred when the propionyl chain is specifically required by the target molecule structure. A mixed anhydride - acetic propionic anhydride - forms as a transient intermediate when the two anhydrides are combined, and can be used as a selective acylating tool.

Q: Is propionic anhydride the same as propanoic anhydride?

Yes - they are identical. Propionic acid is the traditional common name, while propanoic acid is the IUPAC systematic name for CH₃CH₂COOH. Accordingly, their anhydride is correctly named both "propionic anhydride" and "propanoic anhydride." Similarly, the terms propanoic acid anhydride and propionic acid anhydride are interchangeable. All refer to CAS 123-62-6, molecular formula C₆H₁₀O₃.

Q: What are the main uses of propionic anhydride in pharmaceuticals?

In pharmaceutical synthesis, propionic anhydride is primarily used as a propionylation agent for the synthesis of: (1) NSAID drugs - Ibuprofen (via the Hoechst–Celanese or BHC process), Naproxen, and Ketoprofen all involve propionic acid derivatives; propionic anhydride efficiently installs the propionyl group in key intermediate steps. (2) Steroid derivatives - propionylation of hydroxyl groups in steroidal APIs. (3) Antibiotic intermediates - acylation of amine groups in beta-lactam and macrolide synthesis. Its clean by-product profile (only propionic acid) and compatibility with GMP processes make it the preferred acylating agent over propionyl chloride in regulated pharmaceutical manufacturing.

Q: What mixed anhydrides can be formed with propionic anhydride?

Propionic anhydride can react with other carboxylic acids or their anhydrides to form mixed anhydrides. Key examples: acetic propionic anhydride (from acetic anhydride + propionic acid or propionic anhydride + acetic acid) - used as a selective acylating agent; formic propionic anhydride - used in formylation reactions; benzoic propanoic anhydride - a mixed benzoic/propionic anhydride for selective acylation of less reactive substrates; butyric propionic anhydride - for synthesis of mixed ester polymers. These mixed anhydrides are typically prepared in situ rather than isolated, using propionic anhydride as the starting material.

Q: What is the propionic anhydride SDS / MSDS classification?

Key SDS highlights: GHS hazard classifications - Skin Corrosion/Irritation Category 1 (causes severe burns), Serious Eye Damage Category 1, Acute Toxicity (inhalation) Category 4, Flammable Liquid Category 3 (flash point 63°C). UN number: 2215, Class 8 (corrosive liquid), Packing Group II. Store away from moisture, bases, and oxidizers. In case of fire, use dry powder or CO₂ - do NOT use water (hydrolysis releases corrosive propionic acid). Full SDS/MSDS PDF available from sales@sinolookchem.com.