The heterocyclic aromatic six-membered pyrimidine has two nitrogen atoms in positions 1 and 3, with two more diazine forms and isomers. Pyrimidine derivatives have wide applications in pharmaceutical drugs and medicinal chemistry since purines and pyrimidines are two components of nucleic acids [1]. Moreover, the fluorinated pyrimidines (FPs) such as 5-Fluorocytosine (5-FC) and 5-Fluorouracil (5-FU) are found efficacious in treating cancer because they are artificial/synthetic structural analogues of DNA nucleotides [2]. Therefore, understanding the vibrational modes of pyrimidine compounds is considered vital in different domains such as spectroscopy and biology, to provide insights into their molecular interactions, and kinetics studies. In 1950's up to 1970's, the vibrational spectra of pyridazine, pyrimidine, and pyrazine were investigated [3,4]. In 1974 a set of Urey-Bradley and valence force field (VFF) constants were predictable for pyrimidine (-d0 & -d4), to predict the vibrational frequencies of 2-Chloropyrimidine. More recently, the vibrational spectra of pyrimidine and its derivatives have been subjected to numerous studies [[5], [6], [7], [8], [9], [10]]. Nevertheless, the vibrational spectra of 2,4,6-Trifluoropyrimidine [11], and that of 5-chloro-2,4,6-trifluoropyrimidine (CTFP) have already been investigated based on the C2v point group [5]. It must be noted that an alternative available paper by Parimala and coworkers for CTFP [6] is undoubtedly a source of recurrence and almost verbatim to that already published [5], including hyperpolarizabilities, NBO Analysis, ADMET Studies, chemical reactivity, and in-silico ligand-protein docking! They have provided tentative vibrational interpretations using HF frequency calculations and the MOLVIB program [12]. However, the molecular symmetry, normal modes descriptions, spanned irreducible representations (symmetry species, A1, A2, B1, and B2), infrared and Raman intensities were ignored, nevertheless they provided incorrect wavenumbers for CTFP [5]. Meanwhile, the lack of genuine stretching/bending force constants (FCs) in internal coordinates and reliable potential energy distributions (PEDs) inspired us to reinvestigate the CTFP molecule. This work aims to establish a precise/reliable quantitative vibrational analysis for CTFP molecule, improving upon prior literature by delivering an accurate normal mode description and addressing previous methodological oversights. Therefore, we have initiated quantum chemical calculations (QCC) using diverse methods of density functional theory (DFT), B3LYP [13,14], B3PW91 [15], B3PW86 [16], and ωB97XD [17] in addition to Møller–Plesset second perturbation theory [18] (MP2 = full) to obtain adequate geometry in addition to vibrational frequencies. Our revised vibrational assignments suggested herein based on internal coordinates definitions, will be compared with those reported earlier for halogenated pyrimidine skeletons whenever appropriate. Finally, MOLVIB and VEDA outcomes will be evaluated for CTFP molecule, in addition to those recently released for selected polyatomic organic compounds [[19], [20], [21], [22]], which will also be assessed comprehensively.