UV-Vis spectroscopy Ultraviolet-Visible spectroscopy is a technique that measures the absorption of light by a compound in the ultraviolet and visible regions of the electromagnetic spectrum. This absorption is related to the electronic transitions within the molecules, and the resulting spectra can provide information about the structure and functional groups present in the compound.To identify the presence of -OH functional group hydroxyl group in a given organic compound using UV-Vis spectroscopy, you can follow these steps:1. Prepare a suitable sample: Dissolve the organic compound in an appropriate solvent that does not absorb in the UV-Vis region of interest e.g., methanol or acetonitrile . The concentration should be such that the absorbance values fall within the range of 0.1 to 1.0 for accurate measurements.2. Record the UV-Vis spectrum: Using a UV-Vis spectrophotometer, record the absorption spectrum of the sample over a wavelength range of around 200 to 800 nm. The instrument will plot the absorbance values against the wavelength, resulting in a spectrum.3. Analyze the spectrum: Look for characteristic absorption bands that can be attributed to the presence of the -OH functional group. The hydroxyl group typically shows absorption bands in the following regions: a. O-H stretching: A broad absorption band in the range of 3200 to 3600 cm-1 infrared region due to the O-H stretching vibration. This band is not directly observable in the UV-Vis region but can be detected using complementary techniques like FTIR spectroscopy. b. Electronic transitions: The presence of a hydroxyl group can lead to electronic transitions in the UV region, typically below 250 nm in the case of alcohols and phenols . These transitions are often associated with n* and n* transitions, where n represents a non-bonding electron pair on the oxygen atom, and * and * represent antibonding orbitals.4. Compare with reference spectra: To confirm the presence of the -OH functional group, compare the obtained spectrum with reference spectra of known compounds containing the hydroxyl group. This can help in identifying the characteristic absorption bands and provide further evidence for the presence of the -OH group.5. Complementary techniques: It is essential to use complementary techniques like FTIR, NMR, or mass spectrometry to confirm the presence of the -OH functional group, as UV-Vis spectroscopy alone might not provide definitive evidence.In summary, while UV-Vis spectroscopy can provide some indication of the presence of the -OH functional group in a given organic compound, it is essential to use complementary techniques to confirm the presence of the hydroxyl group and obtain a more comprehensive understanding of the compound's structure.