Auxochrome

Auxochrome

Auxochrome - this is a group of atoms attached to a chromophore which modifies the ability of that chromophore to absorb light. Example: -OH , - NH2 , Aldehydes.

An auxochrome is a functional group of atoms with nonbonded electrons which, when attached to a chromophore, alters both the wavelength and intensity of absorption. If these groups are in direct conjugation with the pi-system of the chromophore, they may increase the wavelength at which the light is absorbed and as a result intensify the absorption. 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.

It increases the color of any organic compound. For example, Benzene cant develop color as it doesnt have any chromophore but Nitro benzene is pale yellow color because of the presence of nitro compound. But when it is para-hydroxynitro benzene, the color is deep yellow. Here an auxochrome (-OH) is conjugated with the chromophore -NO2. This is why the color is more developed. Same case happens in Azo benzene (Red color)but para-hydroxy azobenzene is dark red color.

There are mainly two types of auxochromes-

1. Acidic -COOH, -OH, -SO3H2. Basic -NHR, -NR2, -NH2


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  • Auxochrome —   [zu griechisch chrõma »Farbe«] Plural, auxochrome Gruppen, Farbstofftheorie: Atomgruppen mit freien Elektronenpaaren, die bei ihrem Einbau in die Moleküle eines Chromogens im Zusammenwirken mit dessen Chromophoren Farbverschiebungen und… …   Universal-Lexikon

  • auxochrome — [ôk′sə krōm΄] n. [< Gr auxanein, to increase (< auxein: see AUXIN) + CHROME] a radical or atom group, as NH2 or OH, needed to bond organic dyes to fabric fibers …   English World dictionary

  • Auxochrome — Gegenüberstellung von Indigo und Purpur in Ausfärbungen. Purpur als Dibrom Indigo, die zwei Br wirken offensichtlich bathochrom Auxochrome (von griech. auxanein = wachsen und chroma = Farbe) sind funktionelle Gruppen in Farbstoff Molekülen, die… …   Deutsch Wikipedia

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  • Auxochrōme Atomgruppen — Auxochrōme Atomgruppen, s. Farbstoffe …   Meyers Großes Konversations-Lexikon

  • auxochrome — auxochromic, adj. /awk seuh krohm /, n. Chem. any radical or group of atoms that intensifies the color of a substance. [1890 95; AUXO + CHROME] * * * …   Universalium

  • auxochrome — The chemical group within a dye molecule by which the dye is bound to reactive end groups in tissues. The a. enhances the intensity of absorption. [auxo + G. chroma, color] * * * auxo·chrome ȯk sə .krōm n a salt forming group (as hydroxyl or… …   Medical dictionary

  • auxochrome — n. group of atoms which intensify color (Chemistry) …   English contemporary dictionary

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