UV-Vis spectroscopy Ultraviolet-Visible spectroscopy is a technique used to study the interactions of molecules with electromagnetic radiation in the ultraviolet and visible regions of the electromagnetic spectrum. This technique can be used to identify the presence of specific functional groups in a given compound by analyzing the absorption characteristics of these functional groups in the UV-Vis spectrum.When a molecule absorbs UV or visible light, it undergoes electronic transitions, promoting electrons from lower energy levels ground state to higher energy levels excited state . The energy required for these transitions is specific to the functional groups present in the molecule. By analyzing the absorption spectrum, we can identify the functional groups present in the compound.Here are some common functional groups and their absorption characteristics in the UV-Vis spectrum:1. Conjugated systems: Compounds with conjugated double bonds, such as polyenes and aromatic compounds, show strong absorption in the UV region 200-400 nm . The absorption maxima max shift to longer wavelengths bathochromic shift as the extent of conjugation increases.2. Carbonyl groups C=O : Compounds containing carbonyl groups, such as aldehydes, ketones, and carboxylic acids, typically absorb in the UV region 170-300 nm . The absorption maxima depend on the type of carbonyl compound and the presence of any conjugation.3. Nitro groups NO2 : Nitro-containing compounds show strong absorption in both the UV and visible regions 300-600 nm . The absorption maxima depend on the type of nitro compound and the presence of any conjugation.4. Azo groups N=N : Azo compounds, which contain a nitrogen-nitrogen double bond, show strong absorption in the visible region 400-700 nm . The absorption maxima depend on the type of azo compound and the presence of any conjugation.5. Metal complexes: Transition metal complexes often show strong absorption in the visible region due to d-d transitions or charge-transfer transitions. The absorption maxima depend on the type of metal ion, the oxidation state, and the ligands coordinated to the metal ion.To identify the presence of specific functional groups in a given compound using UV-Vis spectroscopy, follow these steps:1. Obtain the UV-Vis absorption spectrum of the compound by recording the absorbance as a function of wavelength.2. Identify the absorption maxima max in the spectrum.3. Compare the absorption maxima with the known absorption characteristics of various functional groups.4. Determine the presence of specific functional groups based on the similarities between the observed absorption maxima and the known absorption characteristics of the functional groups.Keep in mind that UV-Vis spectroscopy is often used in conjunction with other spectroscopic techniques, such as infrared IR spectroscopy and nuclear magnetic resonance NMR spectroscopy, to provide a more comprehensive understanding of the molecular structure and functional groups present in a compound.