Xylenolphthalein

Structural formula
General
Surname	Xylenolphthalein
other names	3,3-bis (4-hydroxy-2,5-dimethylphenyl) -2-benzofuran-1-one ( IUPAC ) 2 ', 5', 2 ", 5" - tetramethylphenolphthalein
Molecular formula	C 24 H 22 O 4
Brief description	beige solid
External identifiers / databases
CAS number 50984-88-8 EC number 256-893-4 ECHA InfoCard 100.051.704 PubChem 628858 Wikidata Q2598536
properties
Molar mass	374.44 g mol −1
Physical state	firmly
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Xylenolphthalein is a triphenylmethane dye and belongs to the phthaleine family. The name is composed of xylenol and phthalic anhydride . It is used as a pH indicator . The corresponding sulfonphthalein is xylenol blue .

properties

At a pH value of 0 to about 9.3, dissolved xylenolphthalein is colorless, at a higher pH value (10.5) the solution turns blue, in a strongly alkaline medium, at a pH value close to 14, it becomes colorless again . It is therefore u. a. used as an indicator in the titration of basic solutions .

Xylenolphthalein is not soluble in water and is mostly used in 0.1% alcoholic solution. It is a weak acid itself.

presentation

In a Friedel-Crafts acylation , p-xylenol (2,5-dimethylphenol) and phthalic anhydride are reacted in the presence of small amounts of concentrated sulfuric acid.

Individual evidence

1. ↑ ^{a b c} data sheet p-Xylenolphthalein for microscopy from Sigma-Aldrich , accessed on February 24, 2013 ( PDF ).