CEC ASSIGNMENT
ORGANIC CHEMISTRY
TOPIC : PHTHALEIN
DYES
NAME : HIRALBA CHUDASAMA
19SC01016
BSC CHEMISTRY
SEM VI
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The topic of phthalein dyes in organic chemistry. It defines what dyes are and how they differ from pigments. It then delves into the specifics of phthalein dyes, including their structure, preparation, and mechanism of action. The document also provides an example of a phthalein dye, phenolphthalein, and its uses as an acid-base indicator. Overall, this document provides a basic understanding of phthalein dyes and their applications in organic chemistry.
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CEC ASSIGNMENT
ORGANIC CHEMISTRY
TOPIC : PHTHALEIN
DYES
NAME : HIRALBA CHUDASAMA 19SC BSC CHEMISTRY SEM VI
WHAT ARE DYES?
- (^) A dye is a colored substance that chemically bonds to the
substrate to which it is being applied. This distinguishes
dyes from pigments which do not chemically bind to the
material they color.
- (^) A dye is colored compound, normally used in solution,
which is capable of being fixed to a fabric.
- (^) Dyes are substances that can be used to impart color to
other materials, such as textiles, foodstuffs and papers
- (^) Dye is generally applied in an aqueous solution, and may
require a mordant to improve the fastness of the dye on
the fiber.
TRIARYLMETHANE DYE
- (^) They are derivatives of triphenylmethane containing -NH2 , - NR2 or -OH groups at para positions as auxochromes. They are however, colorless compounds called leuco bases. These compounds on oxidation give colored bases which on treatment with acid give the salt. The dye contains the quinonoid group as the chromophore.
- (^) In triarylmethane dyes, a central carbon is bonded to three aromatic rings.
- (^) Basic triarylmethane dyes are used for dyeing paper, leather, and plastics, as well as in the manufacture of writing, printing, and stamping inks. Some triarylmethane dyes are used for dyeing polyacrylonitrile fibers.
PHTHALEIN DYES
- (^) They may also be considered as derivatives of triphenylmethane with hydroxy and carboxylic groups. They are prepared by condensation of phthalic anhydride with m-dihydroxyphenols or m-aminophenols in the presence of dehydrating agents.
- (^) Phenolphthalein is a phthalein dye which is colorless in acidic medium and pink in alkaline medium. It is mainly used as an indicator.
- Phthalein dyes are a class of dyes mainly used as pH indicators, due to their ability to change colors depending on pH. They are formed by the reaction of phthalic anhydride with various phenols.
- (^) Example of phthalein dyes are phenolphthalein ( colorless) and Na- salt of phenolphthalein (colored).
EXAMPLE :
- (^) Phenolphthalein : It is a triarylmethane dye but it is better
known as an acid-base indicator. It is a weak acid, which is
colorless in acidic solution and turns puce pink in alkaline
solution. Phenolphthalein is genotoxic. It might cause
oxidative damage and binds to estrogen receptors.
- (^) Phenolphthalein is prepared by heating phthalic anhydride