5-(4-Chlorophenyl) -3H-pyrazol-3-one (CPP) has been synthesized by the reaction of 2-(piperidin-1-yl)acetamide, p-chlorobenzaldehyde and hydrazine hydrate. Structural characterizations were achieved by means of Mass, ¹HNMR (0–20 ppm), ¹³CNMR (0–200 ppm), IR (3500–400 cm⁻¹) and Raman (3500–100 cm⁻¹) spectral measurements. In addition, the regioselectivity of the above synthetic route / mechanistic path was investigated using B3LYP/6–311++G(2d,p) DFT calculations, which is supported by frontier molecular orbital (FMO), olecular lectrostatic otential (MEP) and natural bond orbital (NBO) analysis. Good agreement between the theoretical analysis and experimental synthetic route has been achieved. Molecular interactions, charge delocalization and electrophilic/nucleophilic sites within the reactant species have been also investigated. CPP can undergo internal rotation around C-C single bond; hence it could be either planar or non-planar configurations. Aided by Density Functional Theory (DFT) optimizations implementing a tight convergence criteria, vibrational frequencies and potential energy surface scan were carried out using B3LYP/6–311++G(2d,p), in favor of planar configuration while a saddle point was obtained for the non-planar geometry. A complete vibrational interpretations were proposed herein, assisted by normal coordinate analysis (NCA) and Potential Energy Distributions (PEDs). Finally, global reactivity descriptors; ionization potential (IP), electron affinity (EA), electronegativity (χ), chemical potential (µ), chemical hardness (η), and electrophilicity index were also calculated and found well correlated to the chemical reactivity of the reactant molecules.

5-(4-Chlorophenyl) -3 H -pyrazol-3-one (CPP) 已通过 2-(piperidin-1-yl) 乙酰胺、对氯苯甲醛和水合肼的反应合成。通过质量、¹ HNMR (0–20 ppm)、¹³ CNMR (0–200 ppm)、IR (3500–400 cm ^-1 ) 和拉曼 (3500–100 cm ^-1 )实现结构表征) 光谱测量。此外，使用 B3LYP/6–311++G(2d,p) DFT 计算研究了上述合成路线/机械路径的区域选择性，该计算得到前沿分子轨道 (FMO)、分子静电势 (MEP) 和自然键轨道 (NBO) 分析。理论分析与实验合成路线之间取得了良好的一致性。还研究了反应物物种内的分子相互作用、电荷离域和亲电/亲核位点。CPP 可以围绕 CC 单键进行内部旋转；因此它可以是平面或非平面配置。借助密度泛函理论 (DFT) 优化实现严格的收敛标准，使用 B3LYP/6–311++G(2d, p)，有利于平面配置，同时为非平面几何获得鞍点。本文提出了完整的振动解释，并辅以法线坐标分析 (NCA) 和势能分布 (PED)。最后，全局反应性描述符；还计算了电离势 (IP)、电子亲和力 (EA)、电负性 (χ)、化学势 (μ)、化学硬度 (η) 和亲电指数，发现与反应物分子的化学反应性密切相关。