Thymolphthalein

Structural formula
General
Surname	Thymolphthalein
other names	3,3-bis (4-hydroxy-5-isopropyl-2-methylphenyl) -1 (3 H ) -isobenzofuranone; 5 ', 5' '- diisopropyl-2', 2 '' - dimethylphenolphthalein;
Molecular formula	C 28 H 30 O 4
Brief description	colorless solid
External identifiers / databases
EC number	204-729-7
ECHA InfoCard	100.004.300
PubChem	31316
Wikidata	Q421048
properties
Molar mass	430.55 g mol −1
Physical state	firmly
Melting point	253 ° C
solubility	almost insoluble in water
safety instructions
GHS labeling of hazardous substances	no GHS pictograms
	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 .

Thymolphthalein is a triphenylmethane dye and belongs to the phthalein family. The name is composed of thymol and phthalic anhydride . The corresponding sulfonphthalein is thymol blue . Like phenolphthalein, it is used as a pH indicator .

properties

Thymolphthalein blue color

Thymolphthalein is a white crystalline powder and is practically insoluble in water. It is mostly used in a 0.1% alcoholic solution. It is a weak acid itself.

Dissolved thymolphthalein is colorless at a pH value of 0 to about 9.3, 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 . It is particularly suitable for determining the second equivalence point of phosphoric acid at pH ≈ 9.7.

presentation

In a Friedel-Crafts acylation , 2 equivalents of thymol and 1 equivalent of phthalic anhydride are reacted in the presence of small amounts of concentrated sulfuric acid or zinc chloride.

Individual evidence

↑ ^a ^b ^c ^d ^e data sheet thymolphthalein (PDF) from Merck , accessed on December 25, 2019.
↑ Jander / Jahr: Maßanalyse , 17th edition, de Gruyter, Berlin 2009, p. 123.

Web links

Commons : Thymolphthalein - Collection of Images, Videos, and Audio Files

Website with 3D model of the molecule

[merck-1] ↑ ^a ^b ^c ^d ^e data sheet thymolphthalein (PDF) from Merck , accessed on December 25, 2019.

[2] Jander / Jahr: Maßanalyse , 17th edition, de Gruyter, Berlin 2009, p. 123.