4-Methyl-5-phenyl-1H-pyrazol-3(2H)-one

Area of Science:

• Crystallography
• Organic Chemistry
• Chemical Physics

Background:

• Crystallization is a crucial process in determining the solid-state structure of organic compounds.
• Tautomerism, particularly enol-keto tautomerism, significantly influences molecular geometry and reactivity.
• Understanding intermolecular interactions is key to predicting crystal packing and material properties.

Purpose of the Study:

• To elucidate the crystal structure of the title compound C(10)H(10)N(2)O.
• To investigate the occurrence of enol-to-keto tautomerism in the solid state.
• To characterize the intermolecular interactions and hydrogen bonding patterns in the crystal.

Main Methods:

• Single-crystal X-ray diffraction was employed to determine the molecular and crystal structure.
• Geometric parameters, including bond lengths and dihedral angles, were analyzed.
• Analysis of hydrogen bonding networks was performed to identify crystal packing motifs.

Main Results:

• The asymmetric unit contains two independent molecules (A and B) of C(10)H(10)N(2)O, both adopting the keto form.
• Similar geometries were observed in both molecules, with C=O bond lengths of approximately 1.288 Å.
• Pyrazole and phenyl rings exhibit distinct dihedral angles (36.67° and 41.19°), and intermolecular hydrogen bonds form dimers and ribbons.

Conclusions:

• The compound C(10)H(10)N(2)O undergoes enol-to-keto tautomerism during crystallization.
• The crystal structure is stabilized by a network of intermolecular N-H⋯O hydrogen bonds, forming R(2)(2)(8) and R(4)(2)(10) ring motifs.
• The study provides insights into the solid-state behavior and structural characteristics of this organic compound.