Phthalein dye

Chemical structure of phenolphthalein, a common phthalein dye

Phthalein dyes are a class of dyes mainly used as pH indicators, due to their ability to change colors depending on pH.[1] They are formed by the reaction of phthalic anhydride with various phenols. They are a subclass of triarylmethane dyes.

Common phthalein dyes include:

• Bromothymol blue
• Bromocresol green
• Bromocresol purple
• Cresol Red
• o-Cresolphthalein
• Chlorophenol red
• Dixylenolphthalein
• Guaiacolphthalein
• α-Naphtholphthalein
• Phenolphthalein
• Phenolsulfonphthalein
• Tetrabromophenolphthalein
• Thymol blue
• Thymolphthalein
• Xylenolphthalein

See also

• Triarylmethane dye

References

1. Sabnis, Ram W. (2010). "Phthalein Dyes". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.phthsabn.a01. ISBN 978-0471238966.