## 1 Introduction  
Chemical reagents play a crucial role in the chemical and pharmaceutical fields as well as several other areas. The Grignard reagent, having the molecular formula R-MgX (where R is an alkyl or an aryl group), is a widely used type of organometallic reagent formed by the reaction of an alkyl halide and magnesium metal in an ethereal solvent, which provides the ligands that stabilize the organo-magnesium compound formed by complexation of ether oxygen at the magnesium center. \[\mathrm{CH_{3}CH_{2}Br+Mg+C_{2}H_{5}OC_{2}H_{5}\ \rightarrow\ CH_{3}CH_{2}MgBr} \tag{1}\]The reagent was named after [PERSON] (1871-1935), who jointly received the Nobel Prize in chemistry with [PERSON] in 1912. The Grignard reaction is an easy method to synthesize various organic compounds required for different chemical reactions, owing to the formation of a new C-C bond. The reagent works as an active pharmaceutical ingredient (API) and thus plays an important role in pharmaceutical industries [1] in the synthesis of various drugs. Moreover, the Grignard reagent is used for the industrial preparation of Tamoxifen, [2] which is used in the early treatment of breast cancer in both men and women [3]. Further, the reagent is used in the synthesis of 5-(4'-methylbiphenyl-2-yl)-1H-tetrazole, [4] which is a key intermediate in the preparation of several angiotensin II receptor antagonists. Owing to its wide range of applications and the strong demand for this reagent, it is essential to evaluate its quality by evaluating its possible adulteration. Presently, the widely available methods for quality determination of chemical reagents are high-performance liquid chromatography (HPLC), mass spectrometry (MS), and nuclear magnetic resonance spectroscopy (NMR). These methods are highly accurate and can detect the adulterants in parts per million (ppm) or parts per billion (ppb) levels. However, they have several shortcomings; for instance, they are time-consuming, destructive, and entail high analysis costs, thus limiting their applicability for regular use. Therefore, there is a need to develop a technique that can overcome all the aforementioned drawbacks and provide an alternative tool for the quality measurement of Grignard reagent. Spectroscopy is an effective and imperative tool for investigating the structure of chemically relevant systems. It is useful for extracting information such as structural and other physicochemical properties of molecules by analyzing the interaction of electromagnetic radiation with matter. Further, it is capable of determining atomic and molecular structures and is used for measuring the energy difference between different molecular energy levels. Various spectroscopic techniques are used for measuring experimental parameters, such as the energy of the radiations absorbed or emitted by the molecules, and the intensity of spectral lines. In the case of near-infrared (NIR) absorption, the presence of combination and overtone bands from functional groups in the chemical compounds results in spectra broadness, which reduces the sensitivity, accuracy and precision of spectroscopy [5]. Raman spectroscopy, which is a non-destructive analytical technique that relies on the inelastic scattering of the light by the substances under examination, has garnered considerable attention because of its good analytical performance with pharmaceutical materials. This technique has emerged as a novel technology that can overcome the aforementioned drawbacks of NIR spectroscopy and ensure simultaneous detection of multiple components of mixtures present in samples. Several studies have employed Raman spectroscopy for the quantitative analysis of food and agricultural products, e.g., melamine in liquid milk [6], dairy creams, cream-like analogs [7], fake eggs detection [8], organ oil adulteration [9], etc. Further, Raman spectroscopy was also utilized for pharmaceutical product design [10] and content uniformity of a dry powder inhaler [11].