Synthesis, Crystal Structure, and DFT Study of Ethyl 1-(2-(Hydroxyimino)-2-phenylethyl)-3-phenyl-1H-pyrazole-5-carboxylate

Jin-Hui Zhou,Guo-Qiang Shangguan,Jing Liu,Mao-Jian Shi,Mao-Cai Yan,Liang-Wen Zheng

doi:10.1155/2017/6537402

Jin-Hui Zhou, Guo-Qiang Shangguan + Show 4 more

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https://doi.org/10.1155/2017/6537402

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Abstract

The crystal structure of ethyl 1-(2-(hydroxyimino)-2-phenylethyl)-3-phenyl-1H-pyrazole-5-carboxylate has been determined by X-ray single crystal diffraction. The crystal of the title compound is the monoclinic space group P2/c with unit cell parameters of a=8.634(2) Å, b=9.616(2) Å, c=22.190(3) Å, β=99.2652°, V=1818.3(4) Å3, and Z=4. The dihedral angles formed by the planes of the central pyrazole ring and the adjacent benzene rings are 73.60(7)° and 3.55(7)°, respectively. The combination of the weak intermolecular C-H⋯O and N-H⋯O hydrogen-bonding interactions stabilizes the crystal packing. The geometries of its Z and E isomers and the corresponding transition state (TS), as well as the dimer of its Z isomer, are optimized using the B3LYP hybrid functional coupled with def-TZVP triple-zeta polarized basis set. The bond angles and bond lengths of the optimized structure of Z dimer are very consistent with those of its single crystal parameters. Double-hybrid functional PWPB95-D3 in combination with very highly accurate basis set def2-QZVP is employed to evaluate accurate energy of each isomer and TS. The calculated equilibrium constant between Z and E isomers corresponds to the [Z]/[E] ratio of 4.29. Mulliken atomic charges and electrostatic potential (ESP) on molecular van der Waals (vdW) surface are calculated in order to study and predict the intermolecular interactions. The molecular total energies and frontier orbital analysis are also discussed.

Highlights

Pyrazole oximes are one class of heterocyclic compounds which play a key role in the field of chemistry and pharmacology
The geometries of Z and E isomers and the corresponding transition state (TS), as well as the dimer of its Z isomer, are optimized using B3LYP hybrid functional coupled with def-TZVP triple-zeta polarized basis set
The geometries of Z and E isomers as well as the corresponding transition state (TS) are optimized using B3LYP hybrid functional [19] coupled with def-TZVP triple-zeta polarized basis set [20] within Gaussian 03 package [21]

Summary

Introduction

Pyrazole oximes are one class of heterocyclic compounds which play a key role in the field of chemistry and pharmacology. The structure of ethyl 1-(2-(hydroxyimino)2-phenylethyl)-3-phenyl-1H-pyrazole-5-carboxylate is determined by single crystal X-ray diffraction [15, 16]. Its configuration of oxime bond and intermolecular interactions is confirmed. We have conducted density functional theory (DFT) calculations to prove that selected hybrid functionals and basis sets are suitable for the calculations of the structural parameters, intermolecular hydrogen bonds, and equilibrium constant between Z and E isomers for oximes. This work provides a possibility to predict these parameters when a certain compound lacks its single crystal. The single crystal structure is Z configuration. It is expected that the intermolecular hydrogen bonds must exist in title compound’s molecular crystal. The frontier orbital analysis and molecular total energies are discussed

Experimental

Results and Discussion

Conclusion