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Chromophores

Chromophores are groups of atoms that absorb light at specific wavelengths, giving compounds their distinctive colors. Examples include chlorophyll, which gives plants their green color, and carotenoids like beta-carotene that give carrots their orange hue. Chromophores contain conjugated bonds that allow electrons to absorb light in a way that we see as color. While all colored compounds contain chromophores, not all chromophore-containing molecules appear colored. A major application is in synthetic dyes, where chromophores impart color to textiles and are named based on their functional groups like nitroso or azo groups. Chromophore chemistry underlies different dye types like acid or basic dyes. Auxochromes can intensify or

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341 views2 pages

Chromophores

Chromophores are groups of atoms that absorb light at specific wavelengths, giving compounds their distinctive colors. Examples include chlorophyll, which gives plants their green color, and carotenoids like beta-carotene that give carrots their orange hue. Chromophores contain conjugated bonds that allow electrons to absorb light in a way that we see as color. While all colored compounds contain chromophores, not all chromophore-containing molecules appear colored. A major application is in synthetic dyes, where chromophores impart color to textiles and are named based on their functional groups like nitroso or azo groups. Chromophore chemistry underlies different dye types like acid or basic dyes. Auxochromes can intensify or

Uploaded by

Arshdeep Kaur
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
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Chromophores (from the Greek chroma, or "color," and phoros, or

"bearer") are groups of atoms in an organic compound that absorb light


at certain wavelengths. A particular chromophore gives the compound its
distinctive color by causing it to absorb light selectively.An example of a
chromophoric compound ischlorophyll, the plant pigment that gives
vegetation its green color.
Over the eons, photosynthetic organisms such as trees, plants, algae, and
some bacteria have evolved a set of chromophoric pigments that
efficiently capture sunlight, which they convert to energythat they use to
sustain themselves. Other examples include beta-carotene which is
responsible for the orange color of carrots. It is also added to most butter
and margarine products to provide a yellow color. Lycopene is another
type of plant pigment that gives tomatoes their red color. An example of
a synthetically derived chromaphore is malachite green, a material that is
used as a textile dye.
Scientists once thought chromophores such as these were the source of
colored light, but now they know that color comes from the reflection of
particular wavelengths of light that the chromophore does not absorb.
Chromophores interact with light in a unique way because they contain
conjugated bonds, which consist of a network of alternating double and
single bonds. The electrons in these bond arrangements are spread
throughout themolecule in such a way that they absorb light in a specific
fashion. The unabsorbed light (either reflected or transmitted) is what we
see as the color of the material. While researchers have discovered all
colored compounds do indeed contain one or more chromophores, not all
chromophore containing compounds are colored.
One of the major practical applications of chromophore chemistryis in
the manufacture of synthetic dyes, or dyestuffs, for textiles. Each dye
molecule has one or more chromophores that give the textile its
characteristic color. In fact, the dyes are named after their chromophores,
e.g., the nitroso group, the azo group, thecarbonyl group, the thio
group, and the nitro group.
Chromophore chemistry varies widely in industrial dyeing applications. In
acid dyes, which are good for dyeing wool, silk, and acrylics, the
chromophores are part of a negative ion. Chromophores in metallized
dyes contain a chelated (tightly bound) metal atom. In basic dyes, used
mainly for acrylics, the chromophores are part of a positive ion. Some of
the dyes to which chromophores give a vibrant color are naphthol yellow,
vat blue, congo red, and methylene blue. Chromophores are also
important in direct, vat, sulphur, disperse, and reactive dye chemistry.
The color produced by chromophores may be intensified or shifted by
other groups of atoms on the molecule. These auxiliary groups, known as
auxochromes, can change the absorption characteristics of chromophores.
Examples of auxochromes include amino groups, halogen atoms, hydroxyl
groups, and alkoxyl groups

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