Final answer:
In UV spectrophotometry, a compound that absorbs in the range of 200-400nm involves specific electronic transitions, such as π - π* transitions in conjugated systems, and gives insight into the presence of chromophores within a molecule.
Step-by-step explanation:
When a compound absorbs light within the UV-vis range of 200-400nm, it often involves electronic transitions within the molecule. For example, in the UV spectrophotometer, compounds with conjugated pi systems or chromophores, like aromatic amino acids or 4-methyl-3-penten-2-one, can absorb light at specific wavelengths due to these electronic transitions. The observed color of a solution is the complement of the absorbed wavelength; if a compound's absorbance maxima, or Amax, is at 630 nm in the orange part of the spectrum, the compound would appear blue as a result of transmitting blue light.
When discussing the Beer-Lambert Law, the relationship between a chromophore's concentration and its absorbance at a given wavelength is described.
The absorbance peak and wavelength of maximum absorbance provide crucial information about the compound, such as the presence of certain functional groups. An absorbance peak between 260 nm to 290 nm suggests the presence of aromatic amino acids, while a peak at 236 nm followed by another at 314 nm in 4-methyl-3-penten-2-one indicates π - π* transitions and lone pair to π* antibonding molecular orbital transitions.