p-Toluenesulfonic Acid Monohydrate (CAS 6192-52-5) – High-Purity Catalyst & Organic Intermediate

Product Overview

p-Toluenesulfonic acid monohydrate (PTSA monohydrate, Tosylic acid monohydrate) is a strong organic acid widely used as a catalyst in esterification, acetalization, and condensation reactions.

• CAS Number: 6192-52-5

• Molecular Formula: C₇H₈O₃S · H₂O

• Molecular Weight: 190.22 g/mol

• Purity: ≥99.0% (HPLC)

• Melting Point: 103–106 °C (with decomposition)

• Appearance: White to off-white crystalline solid

• Storage: Keep in a cool, dry, well-ventilated area; avoid moisture and strong oxidizers.

Key Properties

PTSA monohydrate is non-volatile and thermally stable under typical reaction conditions. It serves as a convenient source of p-toluenesulfonic acid without the need to handle the anhydrous hygroscopic solid.

Major Applications

1. Organic Synthesis Catalyst

• Esterification reactions: Facilitates the formation of esters from carboxylic acids and alcohols.

• Acetalization & ketalization: Used to protect carbonyl groups in multi-step syntheses.

• Peptide coupling: Acts as an activating agent in certain peptide synthesis protocols.

2. Polymer & Resin Industry

• Polyester production: Catalyzes polycondensation reactions in the manufacture of unsaturated polyesters and alkyd resins.

• Epoxy curing accelerator: Enhances crosslinking in epoxy systems.

3. Pharmaceutical Intermediates

• Key catalyst in the synthesis of active pharmaceutical ingredients (APIs) such as anticoagulants, antiviral agents, and anti-inflammatory drugs.

• Used in the production of tosylate salts to improve drug solubility and bioavailability.

4. Paints, Coatings & Inks

• Promotes the crosslinking reaction of melamine-based coatings.

• Improves hardness and chemical resistance of industrial coatings.

5. Electroplating & Dye Industry

• Acts as an additive to adjust bath acidity and improve metal deposition quality.

Advantages of Using PTSA Monohydrate

• Strong acidity with low corrosiveness compared to mineral acids (e.g., H₂SO₄, HCl).

• Easy to handle – non-oxidizing, stable crystalline solid.

• High selectivity in acid-catalyzed reactions, minimizing side products.

• Recyclable in many industrial processes.

• Mild reaction conditions reduce energy consumption and equipment wear.

Typical Packaging & Supply

• 25 kg fiber drums with inner PE liner

• 500 kg woven bags

• Custom packaging (1 kg, 5 kg, 10 kg) for R&D and lab samples

Aozunchem offers reliable supply of p-Toluenesulfonic acid monohydrate with strict quality control (HPLC, titration, moisture analysis). Each batch includes a Certificate of Analysis (COA).

Frequently Asked Questions (FAQs)

Q1: What is the difference between p-Toluenesulfonic acid monohydrate and the anhydrous form?
The monohydrate contains one water of crystallization. It is less hygroscopic, easier to weigh and store, and has a defined melting point. For most catalytic applications, both forms can be used equivalently (after adjusting for water content). The monohydrate is preferred in routine lab and industrial use due to handling convenience.

Q2: Is PTSA monohydrate corrosive?
Yes, it is a strong organic acid. It can cause severe skin and eye irritation and is corrosive to metals. Appropriate PPE (gloves, goggles, lab coat) and ventilation should be used. Avoid contact with strong bases, oxidizing agents, and reactive metals.

Q3: What is the typical dosage as a catalyst in esterification?
Usually 0.5–5 mol% relative to the limiting reagent. The exact amount depends on the substrates and reaction temperature. In many polyesterifications, 1–3 wt% is sufficient.

Q4: Can I dissolve PTSA monohydrate in organic solvents?
Yes. It is readily soluble in alcohols (methanol, ethanol, isopropanol), acetonitrile, ethyl acetate, acetone, and dioxane. It has limited solubility in nonpolar solvents like hexane or toluene, but slightly warm toluene often works with stirring.

Q5: How should I store p-Toluenesulfonic acid monohydrate?
Store in a tightly sealed container in a cool, dry place (≤30 °C) away from direct sunlight. Keep away from moisture, strong bases, and oxidizing agents. Under proper conditions, shelf life is at least 24 months.

Q6: Is this product listed under any regulatory inventories?
Yes. p-Toluenesulfonic acid monohydrate is registered in TSCA (US), EINECS (EU), ECL (Korea), IECSC (China), and other major chemical inventories. It is not a restricted substance under REACH when used as an intermediate or catalyst.

Q7: What is the water content of the monohydrate form?
Theoretical water content is ~9.5% (1 mole of H₂O per mole of PTSA). Actual analytical values range from 9.0–10.0% depending on storage conditions.

Q8: Can I use PTSA monohydrate in azeotropic water removal reactions?
Yes. The water from the monohydrate can be removed via a Dean-Stark trap or by azeotropic distillation with toluene, benzene, or xylene. For water-sensitive reactions, use the anhydrous form or perform a pre-drying step.

Q9: Is it safe to ship?
Classified as a Class 8 corrosive solid (UN 2585, packing group III). Shipping requires proper hazard labeling and documentation, but it is not explosive or pyrophoric.

Q10: Do you offer free samples?
Yes, Aozunchem provides complimentary lab samples (5–10 g) for qualified R&D evaluations. Shipping fees may apply. Please contact us to request a sample.

Contact Us

For pricing, technical data sheets (TDS/MSDS), or custom packaging inquiries, please reach out:

Email: lisa@aozunchem.com
WeChat / WhatsApp: +86 186 5121 5887