Page 51 - Org 3 theoritical book 2024-25

Clinical Pharmacy PharmD - 2024/2025 Level 2 Pharmaceutical Organic Chemistry-3 (PC 305)
Pyrazoles

Synthesis

1) From 1,3-dicarbonyl compounds:

Condensation of 1,3-dicarbonyl compounds with hydrazine or its derivatives gives

pyrazoles.

Properties

o
• Pyrazole is a colorless solid, mp 70 .
• It is the only one of the trio of 1,2-azoles, (pyrazole, isoxazole and isothiazole), to

be solid at room temperature.

• This might be attributed to intermolecular hydrogen bonding which results in a

dimer formation only in case of pyrazole.

H N
N
N pyrazole dimer
N H

Chemical reactions

a. Electrophilic substitution reactions

Occurs at the 4-position