Basic auxochromes. Auxochrome vs chromophore. Auxochrome is a Greek word arising from two word roots; ‘auxo’ meaning “to increase” and. This lesson explains the parts of a molecule responsible for color: chromophores and auxochromes. Chromophores and auxochromes are. CHROMOPHORE IS THE ACTUAL PART RESPONSIBLE FOR IMPARTING COLOR TO A MOLECULE; AUXOCHROME IS A HELPER THAT.

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G—M List of colors: Similar behavior is seen in azobenzene which has a red color, but p -hydroxyazobenzene is dark red in zuxochromes. A chromophore is the part of a molecule responsible for chroomophores color. Academic Press, New York. A chromophore gives the dye the property of absorbing different radiations whereas auxochrome imparts it with the property of being colored.

In the conjugated chromophores, the electrons jump between energy levels that are extended pi orbitalscreated by a series of alternating single and double bondsoften in aromatic systems.


If the energy incorporated is changed, automatically the wavelength of the radiation it absorbs will also change and the compound will appear colored.

To convert basic dyes to acidic dyes, the negatively charged sulphonic groups anf often used. For example, phenolphthalein is a pH indicator whose structure changes as pH auxochromea as shown in the following table:.

Chromophores are constituents of molecules that absorb or reflect certain colors when light fall on them.

Chromophore – Wikipedia

Chemical compounds Color Chemical reactions. In order to prepare dyes, auxochromes are attached to chromophores so as to achieve the deep color intended for the product. Halochromism occurs when a substance changes color as the pH changes. A feature of these auxochromes is the presence of at least auxochroems lone pair of electrons which can be viewed as extending the conjugated system by resonance. Some of these are metal complex chromophores, which contain a metal in a coordination complex with ligands.


They are capable of absorbing and emitting light of various frequencies. Chromophores with double covalent bond appear to be colored as a result of the heightened state of the electrons.

They themselves fail to produce the colour; but when present along with the chromophores in an organic compound intensifies the colour of the chromogen. Auxochromes are classified as either positively charged or negatively charged. June Learn how and when to quxochromes this template message.

Auxochrome – Wikipedia

Different chdomophores produce different effects in the chromophore which in turn causes absorption of light from other parts of the spectrum. This page was last edited on 30 Septemberat Auxochrome is a group of atoms which will impart a particular color when attached to a chromophore but when present alone, will fail to produce that color.

An auxochrome is a functional group of atoms attached to the chromophore which modifies the ability of the chromophore to absorb light, altering the wavelength or intensity of the absorption. Amino groups are examples of positively charged whereas ajd, hydroxyl and sulphonic groups are examples of negatively charged auxochromes.

However, if an auxochrome is present in the meta position to the chromophore, it does not affect the color. Views Read Edit View history.

The chromophore is the part of the molecule where the energy difference between two different molecular orbitals falls within the range of the visible spectrum and hence absorbs some particular colours from visible light.


Lengthening or extending a conjugated system with more unsaturated multiple bonds in a molecule will tend to shift absorption to longer wavelengths.

Auxochromes are a bunch of atoms that when chromophoores with an appropriate chromophore heighten or enhance the color. There is no need to resubmit your comment.

Auxochromes are molecules which auxochfomes attached to non ionizing compounds yet retain their ability to ionize and affect the ability of absorbing light when attached to a chromophore. Articles with short description.

Difference between auxochrome and chromophore

In biological molecules that serve to capture or detect light energy, the chromophore is the moiety that chromophires a conformational change of the molecule when hit by light. The highly conjugated pi-bonding system of the macrocycle ring absorbs visible light. Views Read Edit View history. Hence the molecule appears coloured. You agree that we have no liability for any damages.

Chromophores also alter the energy in the delocalized systems. Normally, auxochromes which intensify the colour are chosen. A—F List of colors: However, as the pH increases beyond 8. They are used together to make dyes. Retrieved from ” https: Examples of such compounds include bilirubin and urobilinwhich exhibit auxochrmes yellow color.