Naphtholphthalein

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Naphtholphthalein is a chemical compound commonly used as a pH indicator. It is a member of the phthalein family of dyes, which are known for their vivid color changes in response to pH variations.

Chemical Properties

Naphtholphthalein has the chemical formula C28H18O4 and a molar mass of 418.44 g/mol. It is structurally related to other phthalein dyes such as phenolphthalein and thymolphthalein. The compound exhibits a color change from colorless to blue over a pH range of approximately 7.3 to 8.7.

Synthesis

The synthesis of naphtholphthalein typically involves the condensation of naphthol with phthalic anhydride in the presence of a catalyst. This reaction forms the characteristic phthalein structure, which is responsible for its pH-sensitive color change.

Applications

Naphtholphthalein is primarily used as a pH indicator in various chemical and biochemical applications. It is particularly useful in titrations and other analytical procedures where precise pH measurements are required. Additionally, it can be used in laboratory settings to monitor the pH of solutions.

Related Compounds

• Phenolphthalein
• Thymolphthalein
• Bromothymol blue
• Methyl orange

See Also

• pH indicator
• Acid-base titration
• Chemical indicator