UV-Vis spectroscopy is a technique that measures the absorption of ultraviolet UV and visible light by a compound. It can be used to identify the presence of functional groups, such as carbonyl groups or double bonds, in an unknown compound by analyzing the specific absorption characteristics of these functional groups in the UV-Vis spectrum.In UV-Vis spectroscopy, a compound is exposed to a range of wavelengths of UV and visible light. The compound absorbs specific wavelengths of light, which corresponds to the energy required to promote electrons from lower energy levels to higher energy levels. The absorption of light at specific wavelengths is related to the presence of certain functional groups in the compound.To identify the presence of functional groups in an unknown compound using UV-Vis spectroscopy, you would first obtain the UV-Vis spectrum of the compound. This spectrum is a plot of absorbance or transmittance versus wavelength. The specific absorption characteristics of different functional groups can then be compared to the spectrum of the unknown compound to determine the presence of these groups.Here are the specific absorption characteristics of carbonyl groups and double bonds in the UV-Vis spectrum:1. Carbonyl groups C=O : Carbonyl groups typically absorb light in the UV region, with absorption maxima max between 170 and 220 nm. The exact position of the absorption peak depends on the type of carbonyl group e.g., aldehyde, ketone, ester, or amide and the presence of any conjugation in the molecule. Conjugation with other double bonds or aromatic systems can shift the absorption peak to longer wavelengths lower energies , sometimes extending into the visible region.2. Double bonds C=C : Alkenes with isolated double bonds typically absorb light in the UV region, with max between 160 and 190 nm. However, when there is conjugation between multiple double bonds or with other functional groups such as carbonyl groups, the absorption peak shifts to longer wavelengths. For example, conjugated dienes have max values between 200 and 250 nm, while polyenes with more extended conjugation systems can have max values in the visible region, resulting in color.By analyzing the UV-Vis spectrum of an unknown compound and comparing it to the known absorption characteristics of various functional groups, you can identify the presence of carbonyl groups, double bonds, and other functional groups in the compound. Keep in mind that other factors, such as solvent effects and the presence of multiple chromophores in the molecule, can also influence the absorption spectrum. Therefore, it is essential to consider these factors when interpreting the UV-Vis spectrum of an unknown compound.