what are auxochromes ? Give 10 examples
Answers
AUXOCHROMES: It is a group which itself does not act as a chromophore but when attached to a chromophore, it shifts the adsorption towards longer wavelength along with an increase in the intensity of absorption. Some commonly known auxochromic groups are: -OH, -NH2, -OR, -NHR, and –NR2. For example: When the auxochrome –NH2 group is attached to benzene ring. Its absorption change from λ max 225 (ɛmax 203) to λmax 280 (εmax1430)
All auxochromes have one or more non-bonding pairs of electrons. If an auxochromes is attached to a chromophore, it helps is extending the conjugation by sharing of non-bonding pair of electrons as shown below.
CH2 = CH – NR2 ------------- > CH2-CH-NH2
The extended conjugation has been responsible for bathochromic effect of auxochromes.
An auxochrome is a group of atoms attached to a chromophore which modifies the ability of that chromophore to absorb light.Examples include the hydroxyl group (−OH), the amino group (−NH2), the aldehyde group (−CHO), and the methyl mercaptan group (−SCH3)