1,2-Dihydro-3H-pyrazol-3-one

Also known as: 1,2-dihydropyrazol-3-one, 1H-Pyrazol-3(2H)-one, 1H-Pyrazol-5-ol, 1H-pyrazol-3-ol, 3-Pyrazolone, 3H-PYRAZOL-3-ONE, 1,2-DIHYDRO-, 4-Pyrazolin-3-one, NSC 520837, Pyrazol-3-ol, Pyrazol-5-ol

1,2-Dihydro-3H-pyrazol-3-one (CAS 137-45-1) is a compound in the Pharma Intermediates category listed in the Jingsj chemical database. It has the molecular formula C3H4N2O and a molecular weight of 84.077 g/mol. Key properties include a melting point of 163 °C, a boiling point of 326.1±15.0 °C at 760 mmHg, a density of 1.4±0.1 g/cm3 and a flash point of 151.0±20.4 °C. No supplier offers are currently listed; request a quote. Record last updated Aug 21, 2026.

CAS No.: 137-45-1
Jingsj CID: J-1307609-0
Molecular Formula: C₃H₄N₂O
Molecular Weight: 84.077 g/mol
Category: Pharma Intermediates
Last updated: 8/21/2026

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Physicochemical Properties

Melting Point	163 °C
Boiling Point	326.1±15.0 °C at 760 mmHg
Density	1.4±0.1 g/cm3
Flash Point	151.0±20.4 °C
Exact Mass	84.032364
PSA	48.65000
LogP	0.25
Vapor Pressure	0.0±0.7 mmHg at 25°C
Refractive Index	1.612

Frequently Asked Questions

What is the CAS number of 1,2-Dihydro-3H-pyrazol-3-one?

The CAS number of 1,2-Dihydro-3H-pyrazol-3-one is 137-45-1.

What are the molecular formula and molecular weight of 1,2-Dihydro-3H-pyrazol-3-one?

1,2-Dihydro-3H-pyrazol-3-one has molecular formula C3H4N2O and molecular weight 84.077 g/mol.

What are the upstream and downstream products of 1,2-Dihydro-3H-pyrazol-3-one?

For 1,2-Dihydro-3H-pyrazol-3-one, Downstream Products: Pyrazole.

Data compiled from public chemical databases such as PubChem and supplier catalogs; supplier offers are provided by suppliers.

Last updated: 8/21/2026

How to cite: Jingsj. "1,2-Dihydro-3H-pyrazol-3-one (CAS 137-45-1)". Jingsj Chemical Database. https://www.jingsj.com/compound/J-1307609-0 (accessed 2026-11-09).

Data for reference only; verify product details with suppliers before purchase.