UV-Vis spectroscopy Ultraviolet-Visible spectroscopy is a technique used to study the absorption of light by molecules in the ultraviolet and visible regions of the electromagnetic spectrum approximately 200-800 nm . This absorption of light occurs when electrons in the molecule are excited from their ground state to a higher energy state, which is typically associated with the presence of specific functional groups in the compound.To identify the presence of a specific functional group in a compound using UV-Vis spectroscopy, one can analyze the absorption spectrum of the compound and compare it to the known absorption spectra of various functional groups. The presence of characteristic peaks or bands in the spectrum can indicate the presence of specific functional groups.Here are some examples of compounds and their functional groups that can be identified using UV-Vis spectroscopy:1. Conjugated systems: Compounds with conjugated double bonds or alternating single and double bonds, such as polyenes, can be identified using UV-Vis spectroscopy. The absorption peaks in the spectrum are due to the -* transitions in the conjugated system. For example, -carotene, a naturally occurring pigment, has a strong absorption peak around 450 nm due to its conjugated double bond system.2. Aromatic compounds: Aromatic compounds, such as benzene and its derivatives, can be identified using UV-Vis spectroscopy. The absorption peaks in the spectrum are due to the -* transitions in the aromatic ring. For example, nitrobenzene has a strong absorption peak around 280 nm due to the presence of the aromatic ring and the nitro group.3. Carbonyl compounds: Compounds containing carbonyl groups C=O , such as aldehydes, ketones, and carboxylic acids, can be identified using UV-Vis spectroscopy. The absorption peaks in the spectrum are due to the n-* and -* transitions in the carbonyl group. For example, acetone has a strong absorption peak around 280 nm due to the presence of the carbonyl group.4. Transition metal complexes: Compounds containing transition metals, such as iron, copper, and cobalt, can be identified using UV-Vis spectroscopy. The absorption peaks in the spectrum are due to the d-d transitions in the metal ions or charge-transfer transitions between the metal ions and the ligands. For example, the [Fe CN 6]3- complex has a strong absorption peak around 420 nm due to the charge-transfer transition between the iron ion and the cyanide ligands.In summary, UV-Vis spectroscopy can be used to identify the presence of specific functional groups in a compound by analyzing the absorption spectrum and comparing it to the known absorption spectra of various functional groups. This technique can be applied successfully to various types of compounds, including conjugated systems, aromatic compounds, carbonyl compounds, and transition metal complexes.