UV-Vis spectroscopy can be used to identify the presence of specific functional groups in a given organic compound by analyzing the absorption of ultraviolet UV and visible light by the compound. Here is a step-by-step explanation of the process:1. Prepare the sample: Dissolve the organic compound in a suitable solvent, usually one that does not absorb UV or visible light in the wavelength range of interest.2. Set up the spectrophotometer: The spectrophotometer should be set to scan the desired wavelength range, typically between 200 and 800 nm for organic compounds.3. Measure the background spectrum: Measure the absorption spectrum of the solvent alone to account for any background absorption.4. Measure the sample spectrum: Measure the absorption spectrum of the sample solution, which will include both the background and the compound of interest.5. Subtract the background: Subtract the background spectrum from the sample spectrum to obtain the absorption spectrum of the compound of interest.6. Analyze the spectrum: Identify the characteristic absorption bands in the spectrum that correspond to specific functional groups.Functional groups that can be detected using UV-Vis spectroscopy include:- Conjugated systems: These systems absorb UV light due to the presence of delocalized electrons. The more extended the conjugation, the longer the wavelength absorbed.- Chromophores: Functional groups that absorb light in the visible region, such as azo -N=N- , nitro -NO2 , and carbonyl -C=O groups.- Auxochromes: Functional groups that do not absorb light themselves but can enhance the absorption of chromophores when attached to them, such as hydroxyl -OH and amino -NH2 groups.Limitations of UV-Vis spectroscopy:- Insensitivity to non-chromophoric functional groups: UV-Vis spectroscopy is not effective for detecting functional groups that do not absorb light, such as alkyl and ether groups.- Overlapping absorption bands: The presence of multiple functional groups in a compound can lead to overlapping absorption bands, making it difficult to identify individual functional groups.- Concentration dependence: The absorption of light is dependent on the concentration of the compound, which can affect the accuracy of the analysis if not properly controlled.Example:Compound: p-Nitroaniline C6H6N2O2 UV-Vis spectrum:- Absorption band at ~380 nm: This band corresponds to the -* transition of the conjugated system formed by the benzene ring and the nitro group.- Absorption band at ~270 nm: This band corresponds to the n-* transition of the nitro group.- Absorption band at ~230 nm: This band corresponds to the -* transition of the benzene ring.By analyzing the UV-Vis spectrum of p-nitroaniline, we can identify the presence of the benzene ring and the nitro functional group in the compound.