UV-Vis spectroscopy is a technique that measures the absorption of ultraviolet UV and visible light by a compound. This absorption occurs when electrons in the compound are excited from their ground state to a higher energy level by absorbing photons of specific wavelengths. The resulting absorption spectrum can be used to identify the presence of specific functional groups in a compound, such as alcohols or carbonyls.To identify the presence of specific functional groups using UV-Vis spectroscopy, one must look for characteristic absorption bands in the UV-Vis spectra that are associated with the electronic transitions of these functional groups. Here are the key features in the UV-Vis spectra that indicate the presence of alcohols and carbonyls:1. Alcohols:Alcohols have an O-H bond, which results in a broad and intense absorption band in the UV region, typically between 320-360 nm. This band is due to the n* transition, where a non-bonding electron n on the oxygen atom is excited to the antibonding * orbital of the O-H bond. The exact position of the absorption band depends on the specific alcohol and its environment e.g., hydrogen bonding . It is important to note that the presence of other functional groups with O-H or N-H bonds, such as carboxylic acids or amines, can also result in similar absorption bands.2. Carbonyls:Carbonyl compounds, such as aldehydes, ketones, and carboxylic acids, have a C=O bond. The absorption bands associated with carbonyl groups are due to the * transition, where an electron in the bonding orbital is excited to the * antibonding orbital. The absorption bands for carbonyl groups typically appear in the UV region, between 170-220 nm for aldehydes and ketones, and around 200-300 nm for carboxylic acids and esters. The exact position of the absorption band depends on the specific carbonyl compound and its conjugation with other functional groups. For example, conjugation with a C=C double bond or an aromatic ring can shift the absorption band to a longer wavelength lower energy .In summary, to identify the presence of specific functional groups such as alcohols or carbonyls using UV-Vis spectroscopy, one must look for the characteristic absorption bands in the UV region associated with their electronic transitions. For alcohols, this involves the n* transition of the O-H bond, resulting in a broad absorption band between 320-360 nm. For carbonyls, the * transition of the C=O bond results in absorption bands between 170-220 nm for aldehydes and ketones, and around 200-300 nm for carboxylic acids and esters.