5-Methyl-4-isoxazolecarboxylic acid
- CAS No.
- 42831-50-5
- Chemical Name:
- 5-Methyl-4-isoxazolecarboxylic acid
- Synonyms
- 5-METHYLISOXAZOLE-4-CARBOXYLIC ACID;TIMTEC-BB SBB005909;Leflunomide Impurity D;Lefluonamide Impurity D;LeflunoMide EP IMpurity D;Leflunomide impurities1343;Methylisoxazole-4-carboxylic;5-Methyl-4-isoxazolecarboxyl;5-METHYLISOXAZOLE-4-CARBOXYLIC;5-methylisoxazole-4-formic acid
- CBNumber:
- CB8342928
- Molecular Formula:
- C5H5NO3
- Molecular Weight:
- 127.1
- MDL Number:
- MFCD00955655
- MOL File:
- 42831-50-5.mol
- MSDS File:
- SDS
- TDS File:
- TDS
| Melting point | 144-148 °C(lit.) |
|---|---|
| Boiling point | 308.3±22.0 °C(Predicted) |
| Density | 1.348±0.06 g/cm3(Predicted) |
| storage temp. | Sealed in dry,Room Temperature |
| solubility | DMSO (Slightly), Methanol (Slightly) |
| form | Solid |
| pka | 2.85±0.25(Predicted) |
| color | White to Pale Brown |
| BRN | 116000 |
| InChI | 1S/C5H5NO3/c1-3-4(5(7)8)2-6-9-3/h2H,1H3,(H,7,8) |
| InChIKey | VQBXUKGMJCPBMF-UHFFFAOYSA-N |
| SMILES | Cc1oncc1C(O)=O |
| CAS DataBase Reference | 42831-50-5(CAS DataBase Reference) |
| FDA UNII | BL2Q213Q2M |
| UNSPSC Code | 12352100 |
| NACRES | NA.22 |
SAFETY
Risk and Safety Statements
| Symbol(GHS) |  GHS07 |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Signal word | Warning | |||||||||
| Hazard statements | H315-H319-H335 | |||||||||
| Precautionary statements | P261-P280a-P304+P340-P305+P351+P338-P405-P501a | |||||||||
| PPE | Eyeshields, Gloves, type N95 (US) | |||||||||
| Hazard Codes | Xi,F | |||||||||
| Risk Statements | 36/37/38-37/38-36-10 | |||||||||
| Safety Statements | 22-26-36/37/39-36-16 | |||||||||
| WGK Germany | 3 | |||||||||
| HazardClass | IRRITANT | |||||||||
| HS Code | 29349990 | |||||||||
| Storage Class | 11 - Combustible Solids | |||||||||
| REACH Registrations | Active | |||||||||
| NFPA 704 |
|
5-Methyl-4-isoxazolecarboxylic acid price More Price(67)
| Manufacturer | Product number | Product description | CAS number | Packaging | Price | Updated | Buy |
|---|---|---|---|---|---|---|---|
| Sigma-Aldrich | 633771 | 5-Methylisoxazole-4-carboxylic acid 97% | 42831-50-5 | 10g | $247 | 2026-04-30 | Buy |
| Sigma-Aldrich | 633771 | 5-Methylisoxazole-4-carboxylic acid 97% | 42831-50-5 | 1g | $34.7 | 2023-06-20 | Buy |
| TCI Chemical | M1740 | 5-Methylisoxazole-4-carboxylic Acid >98.0%(T)(HPLC) | 42831-50-5 | 5g | $22 | 2026-04-30 | Buy |
| TCI Chemical | M1740 | 5-Methylisoxazole-4-carboxylic Acid >98.0%(T)(HPLC) | 42831-50-5 | 25g | $71 | 2026-04-30 | Buy |
| Usbiological | 283114 | 5-Methyl-4-isoxazolecarboxylic acid Asreported | 42831-50-5 | 10g | $333 | 2026-06-03 | Buy |
5-Methyl-4-isoxazolecarboxylic acid Chemical Properties, Uses, Production
Chemical Properties
Cream to brown Solid
Uses
5-Methylisoxazole-4-carboxylic Acid (Leflunomide EP Impurity D) is an intermediate for synthesis of Leflunomide (L322750). Herbicidal activities towards Digitaria ciliaris.
Flammability and Explosibility
Non flammable
Synthesis
51135-73-0
42831-50-5
Example 4 Preparation of 5-methylisoxazole-4-carboxylic acid To a two-necked flask equipped with a mechanical stirrer and a horizontal condenser for distillation were added 40.0 g of crude ethyl 5-methyl-4-isoxazolecarboxylate and 44 g of 60% sulfuric acid solution. The mixture was heated to 85°C while the ethanol generated from the reaction was continuously distilled. After 4 hours of reaction, thin layer chromatography (TLC) analysis showed complete disappearance of spots of ester compounds. After cooling the reaction mixture to room temperature, the solid product (16.5 g) was collected by filtration. The filtrate was retained for a second product collection at room temperature. The resulting crude acid was dissolved in 60 mL of 2% acetic acid-toluene mixed solvent and crystallized to give 5-methylisoxazole-4-carboxylic acid (9.5 g) of about 99.9% purity. The crystallized mother liquor was retained for subsequent batch processing. The crystallization process was performed as follows: the crude acid was added to 2% acetic acid-toluene solvent mixture and heated for 30 minutes until dissolved. Separate and remove the brown oil from the bottom of the flask. The upper clear organic phase was carefully transferred to another container and left to crystallize.
References
[1] Patent: US2003/139606, 2003, A1
[2] Letters in Drug Design and Discovery, 2016, vol. 13, # 9, p. 912 - 920
[3] Journal of Heterocyclic Chemistry, 1991, vol. 28, # 2, p. 453 - 457
[4] Yakugaku Zasshi, 1959, vol. 79, p. 836
[5] Chem.Abstr., 1960, p. 1493
5-Methyl-4-isoxazolecarboxylic acid Preparation Products And Raw materials
| Supplier | Tel | Country | ProdList | Advantage | |
|---|---|---|---|---|---|
| J & K SCIENTIFIC LTD. | 18210857532 18210857532 | jkinfo@jkchemical.com | China | 96815 | 76 |
| Meryer (Shanghai) Chemical Technology Co., Ltd. | 4006356688 18621169109 | market03@meryer.com | China | 40202 | 62 |
| INTATRADE GmbH | +49 3493/605464 | sales@intatrade.de | Germany | 3563 | 66 |
| future industrial shanghai co., ltd | 400-0066400 13621662912 | sales@jonln.com | China | 1989 | 65 |
| Alfa Aesar | 400-6106006 | saleschina@alfa-asia.com | China | 30103 | 84 |
| TCI (Shanghai) Development Co., Ltd. | 021-67121386 | Sales-CN@TCIchemicals.com | China | 24512 | 81 |
| Energy Chemical | 400-0056266 | sales8178@energy-chemical.com | China | 44850 | 61 |
| Capot Chemical Co., Ltd | +86 (0) 571 85 58 67 18 | China | 18187 | 66 | |
| Beijing Ouhe Technology Co., Ltd | 13552068683 13522913783 | 2355560935@qq.com | China | 11777 | 60 |
| JinYan Chemicals(ShangHai) Co.,Ltd. | 13817811078 | sales@jingyan-chemical.com | China | 9963 | 60 |
View Latest Price from 5-Methyl-4-isoxazolecarboxylic acid manufacturers
| Image | Update time | Product | Price | Min. Order | Purity | Supply Ability | Manufacturer | |
|---|---|---|---|---|---|---|---|---|
 |
2026-09-16 | 5-Methyl-4-isoxazolecarboxylic acid
42831-50-5
|
0.99 | RongNa Biotechnology Co.,Ltd | ||||
 |
2026-09-16 | 5-Methyl-4-isoxazolecarboxylic acid
42831-50-5
|
1KG | 99%min | 1000KGS | WUHAN FORTUNA CHEMICAL CO., LTD | ||
 |
2026-08-20 | 5-Methyl-4-isoxazolecarboxylic acid
42831-50-5
|
$1.10 | 1g | 99.0% Min | 100 Tons | Dideu Industries Group Limited |
-
- 5-Methyl-4-isoxazolecarboxylic acid
42831-50-5
- 0.99
- RongNa Biotechnology Co.,Ltd
-
- 5-Methyl-4-isoxazolecarboxylic acid
42831-50-5
- 99%min
- WUHAN FORTUNA CHEMICAL CO., LTD
-
- 5-Methyl-4-isoxazolecarboxylic acid
42831-50-5
- $1.10
- 99.0% Min
- Dideu Industries Group Limited
