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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When auxochromes are attached to the molecule, the natural frequency of the chromophore gets changed and thus the colour gets modified. An auxochrome helps a dye to bind to the object that is to be colored. It increases the color of any organic compound. Examples of such compounds include bilirubin and urobilinwhich exhibit a yellow color.

Visible light that hits the chromophore can thus be absorbed by exciting an electron from its ground state into an excited state.

Amino groups are examples of positively charged whereas carboxyl, hydroxyl and sulphonic groups are examples of negatively charged auxochromes. Get New Comparisons in your inbox: 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. Various factors in a chromophore’s structure go into determining at what wavelength region in a chromophofes the chromophore will absorb.

A feature of these auxochromes is the presence of at least one lone pair of electrons which can be viewed as extending the conjugated system by resonance. Auxochromes are a bunch of atoms that when combined with an appropriate chromophore heighten or enhance the color.

Chromophores with double covalent bond appear to be colored as a result of the heightened state of the electrons. A wuxochromes gives the dye the property of absorbing different radiations whereas auxochrome imparts it with the property of being colored.


Principles of Organic Chemistry. Different auxochromes produce different effects in the chromophore which in turn causes absorption of light from other parts of the spectrum. To convert basic dyes to acidic dyes, the negatively charged sulphonic groups are often used.

Auxochrome – Wikipedia

The nature of the central metal can also influence the absorption spectrum of the metal-macrocycle complex or properties such as excited state lifetime.

Please help improve this article by adding citations to reliable sources. Views Read Auxochromee View history. By using this site, you agree to the Terms of Use and Privacy Policy. If the energy incorporated is changed, automatically the wavelength of the radiation it absorbs will also change and the compound will appear colored.

In biological molecules that serve to capture or detect light energy, the chromophore is the moiety that causes a conformational change of the molecule when hit by light. Auxochromes are classified as either positively charged or negatively charged.

Chromophores also alter chromophorws energy in the delocalized systems. The electrons which were in the resting state are elevated into the excited state because of the energy auxochrmes into it.

Color model additive subtractive Color mixing Primary color Secondary color Tertiary color intermediate Quaternary color Quinary color Aggressive color warm Receding color cool Pastel colors Color gradient.


Electrolytic dissociation of the axochromes group helps in binding and it is due to this reason a basic substance takes an acidic dye. The presence of an auxochrome in the chromogen molecule is essential to make a dye. Retrieved from ” https: The highly conjugated pi-bonding system of the macrocycle ring absorbs visible light. There is no need to resubmit your comment.


Hue Dichromatism Colorfulness chroma and saturation Tints and shades Lightness tone and value Grayscale. This change in structure affects a chromophore in the pH indicator molecule. An auxochrome is a functional group of atoms with one or more lone pairs of electrons when attached to a chromophore, alters both the wavelength and intensity of absorption.

Woodward-Fieser rules can be used to approximate ultraviolet -visible maximum absorption wavelength in organic compounds with conjugated pi-bond systems. Because of their limited extent, the aromatic rings only absorb light in the ultraviolet region, and so the compound appears colorless in the pH range.

Chromophores are constituents of molecules that absorb or reflect certain colors when light fall on them. Unsourced material may be challenged and removed. June Learn how and when to remove this template message. From Wikipedia, the free encyclopedia.

Chromophore is that part of the molecule which when exposed to visible light will absorb and reflect a certain color.

Chromophores do not absorb light without the requisite contents but with the presence of an auxochrome there is a shift in the absorption of these chromogens. They are used together to make dyes. Color space Color model additive subtractive Color mixing Primary color Secondary color Tertiary color intermediate Quaternary color Quinary color Aggressive color warm Receding color cool Pastel colors Color gradient.

A chromophore is the part of a molecule responsible for its color.