Chromaphoric compounds are substance that contain chroma. There are functional groups called chromaphores which when added to a saturated hydrocarbon, causes absorption in the UV or visible range, to produce colors. Saturated hydrocarbons are colorless, but when a chromaphore is added to it, a color compound is produced.
E.g. of simple chromaphores include the following:
1. Carbonyl Group
This is a carbon atom bonded to an oxygen atom like in Aldehydes and Ketones.
2. Azo Group
This is a Nitrogen atom bonded to another Nitrogen atom. It absorbs light in the visible UV region. Most synthetic food colors are in the form of azo-dyes. E.g. of an compound with an azo group is Azo Benzene.
3. Nitrate Group
This is a Nitrogen atom bonded between two Oxygen atoms. This chromaphore also absorbs light in the visible UV region.
4. Ethylene Group
This isolated chromaphoric group absorbs light at a wavelength of 190nm. It consists of two double-bonded carbon atoms. The amount of light absorbed by this chromaphoric group as part of a complex compound varies, depending on its molar absorptivity. When a compound contains conjugated ethylene groups, the wavelength for light absorption increases.
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2 comments:
Very insightful.
Thanks for posting!
I just want point out something about ethylene groups as chromaphores. It should be noted that ethylene groups act independently in compounds where they are isolated from each other. i.e. in non-conjugated hydrovarbons.
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