Propylthiouracil
CAS: 51-52-5
Category: Pharmaceutical Intermediates
| Purity | Reagent Grade ≥98%, Standard Grade ≥99%, High-Purity Grade ≥99.5%, Pharmaceutical Grade ≥98.0–100.5% |
| Molecular Formula | C7H10N2OS |
| Molecular Weight | 170.23 |
| Appearance | White to pale-cream crystalline powder or microcrystalline powder |
| Packaging | 100 mg/glass vial, 250 mg/glass vial, 500 mg/glass vial, 1 g/glass vial, 5 g/glass vial, 25 g/HDPE bottle, 100 g/HDPE bottle, or 25 kg/cardboard drum with double PE liners |
| Testing Indicators | Appearance — Visual inspection (white to pale-cream crystalline powder or microcrystalline powder); Melting point — Capillary method (218–220°C, literature; 219°C, IARC; 218–221°C, Puripharma; 218.0–220.0°C, Ruifu Chemical; decomposes); Boiling point — Distillation (355.2°C at 760 mmHg, Puripharma; 373.9±42.0°C, predicted); Flash point — 300°C (ChemicalBook); Density — Hydrometer (1.1880 rough estimate, ChemicalBook; 1.24, Puripharma); Refractive index — 1.5960 (estimate, ChemicalBook); Purity — HPLC-UV (≥98–99.5%, C18 column, acetonitrile:buffer gradient, λ=220–275 nm); Related substances — HPLC (impurity profiling including thiourea, des-propyl analogs, and oxidation products; thiourea limit test per USP/EP); Assay — Titrimetric or HPLC (USP/EP: 98.0–100.5% of C7H10N2OS, calculated on the dried basis; Ruifu Chemical: ≥99.0% (T); Yeasen: ≥98%; Cayman: ≥98%); Loss on drying — Gravimetric (≤0.5%; 105°C, EP/WHO); Residue on ignition — Gravimetric (≤0.1%; sulfated ash, WHO); Heavy metals — Colorimetric/ICP-MS (≤10–20 ppm; limit test, WHO); Thiourea — Colorimetric limit test (≤0.05%, WHO/EP); Identification — FTIR (characteristic peaks: N–H (amide) ~3300–3500 cm⁻¹, O–H (enol) ~3200–3400 cm⁻¹, aromatic C–H ~3000–3100 cm⁻¹, aliphatic C–H ~2850–2950 cm⁻¹, C=O (lactam) ~1650–1680 cm⁻¹, C=S (thioamide) ~1200–1350 cm⁻¹, N–H bend ~1600 cm⁻¹); UV spectrophotometry (λmax 214 nm, logε 4.193; λmax 275 nm, logε 4.199 in methanol, IARC; λmax 207.5 nm, logε 4.188; λmax 260 nm, logε 4.029; λmax 315.5 nm, logε 4.037 in methanol, IARC); ¹H NMR (DMSO-d₆: δ 0.90 ppm triplet CH₃ (propyl), δ 1.60 ppm multiplet CH₂ (propyl), δ 2.20 ppm multiplet CH₂ (propyl, α to ring), δ 5.50 ppm singlet 5-H (pyrimidine), δ 12.00 ppm broad singlet N–H (thioamide), δ 12.50 ppm broad singlet N–H (lactam)); ¹³C NMR (DMSO-d₆: δ 14 ppm CH₃, δ 22 ppm CH₂, δ 31 ppm CH₂ (α to ring), δ 105 ppm C5 (pyrimidine), δ 155 ppm C4 (C=O), δ 180 ppm C2 (C=S)); Mass spectrometry — EI-MS (m/z 170 [M]⁺, 100%; m/z 171 [M+1]⁺, 7.6%; m/z 172 [M+2]⁺, 4.5%, NIST); Water content — Karl Fischer titration (GB/T 6283/EP 2.5.12); pH — Potentiometry (5 g/L slurry, pH 6–7.5 at 20°C, ChemicalBook); Specific optical rotation — Not applicable (achiral compound); BCS Class — 3 (low solubility, low permeability). |
| Storage Notes | Store in a cool, dry, well-ventilated area at 15–30°C. Protect from light, moisture, and air. Keep container tightly sealed in light-protective packaging. Store powder at -20°C for long-term stability (up to 3 years); at 4°C for 2 years. Light-sensitive and air-sensitive material; avoid prolonged exposure to light and humid conditions. The compound is sensitive to light and may be sensitive to air. Store away from strong oxidizing agents, strong acids, strong bases, and incompatible substances (including sulfhydryl-oxidizing agents and divalent metals with which it forms complexes). Use inert atmosphere (nitrogen or argon) for long-term storage if available. |
| Lead Time | 10 days |
Propylthiouracil (INN, also known as PTU, Propacil, Propycil, Prothycil, or Thiuragyl) is a thioamide antithyroid agent and a potent inhibitor of thyroid peroxidase (TPO). It functions by inhibiting the iodination of tyrosine residues on thyroglobulin, blocking the synthesis of thyroid hormones (T3 and T4). It also inhibits type-1 iodothyronine deiodinase (DIO1), preventing the peripheral conversion of T4 to the more active T3. Used as a pharmaceutical intermediate and active pharmaceutical ingredient (API) for the development and quality control of oral tablet formulations (e.g., 25 mg and 50 mg tablets). Approved for clinical use in the treatment of hyperthyroidism, Graves' disease, toxic goiter, and as an adjunct in the management of thyroid storm. Also used for preoperative preparation of hyperthyroid patients prior to thyroidectomy or radioactive iodine therapy. Classified by IARC as Group 2B (possibly carcinogenic to humans) and by NTP as reasonably anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity in experimental animals. ATC code: H03BA02.