The following tables present information about how organic compounds absorb ultraviolet (UV) radiation. While not as informative as infrared correlations, UV can often provide valuable qualitative information. Many common chromophores (that portion of a molecule that is responsible for its color) absorb UV light at characteristic wavelengths, as listed in Table 1. In some cases, extinction coefficients are given for multiple wavelengths. Column definitions for Table 1 are as follows.
Column heading | Definition |
Chromophore | Name of chromophore |
Functional group | Molecular formula of chromophore |
λmax | Wavelength at which the maximum absorption occurs, in nm |
εmax | Extinction coefficient at wavelength specified in column to the left |
Chromophore | Functional group | λmax/nm | εmax | λmax/nm | εmax | λmax/nm | εmax |
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Ether | –O– | 185 | 1000 | ||||
Thioether | –S– | 194 | 4600 | 215 | 1600 | ||
Amine | –NH2– | 195 | 2800 | ||||
Amide | –CONH2 | <210 | — | ||||
Thiol | –SH | 195 | 1400 | ||||
Disulfide | –S–S– | 194 | 5500 | 255 | 400 | ||
Bromide | –Br | 208 | 300 | ||||
Iodide | –I | 260 | 400 | ||||
Nitrile | –C≡N | 160 | — | ||||
Acetylide (alkyne) | –C≡C– | 175–180 | 6000 | ||||
Sulfone | –SO2– | 180 | — | ||||
Oxime | –NOH | 190 | 5000 | ||||
Azido | >C=N– | 190 | 5000 | ||||
Alkene | –C=C– | 190 | 8000 | ||||
Ketone | >C=O | 195 | 1000 | 270–285 | 18–30 | ||
Thioketone | >C=S | 205 | strong | ||||
Esters | –COOR | 205 | 50 | ||||
Aldehyde | –CHO | 210 | strong | 280–300 | 11–18 | ||
Carboxyl | –COOH | 200–210 | 50–70 |