Naphtholphthalein

Structural formula
General
Surname	Naphtholphthalein
other names	3,3-bis (4-hydroxy-1-naphthyl) -2-benzofuran-1-one ( IUPAC ) α-naphtholphthalein
Molecular formula	C 28 H 18 O 4
Brief description	light brown or beige powder
External identifiers / databases
CAS number 596-01-0 EC number 209-875-5 ECHA InfoCard 100,008,979 PubChem 68993 Wikidata Q413919
properties
Molar mass	418.44 g mol −1
Physical state	firmly
Melting point	253-255 ° C
solubility	soluble in ethanol practically insoluble in water
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 .

Naphtholphthalein is a triphenylmethane dye and belongs to the phthaleine family. The name is composed of naphthol and phthalic anhydride . It is used as a pH indicator .

properties

There is a color change area:

• pH 7.3-8.7: color change from colorless-reddish to blue-green

Naphtholphthalein 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 , α-naphthol and phthalic anhydride are reacted in the presence of small amounts of concentrated sulfuric acid.

literature

• Emil Alphonse Werner: “The preparation of α-naphtholphthalein”, in: J. Chem. Soc., Trans. , 1918 , 113 , pp. 20-21; doi : 10.1039 / CT9181300020 .
• WJ Harper, TV Armstrong (Department of Dairy Technology, The Ohio State University, Columbus): “The Alpha-Naphtholphthalein (ANP) Method for Measuring Fat Hydrolysis. II. Application to Cream " ; Nov. 15, 1951 ( PDF file; 428 kB)

Individual evidence

1. ↑ ^{a b} Data sheet naphtholphthalein from Sigma-Aldrich , accessed on December 25, 2019 ( PDF ).
2. ↑ ^{a b c d} Data sheet naphtholphthalein (PDF) from Merck , accessed on December 25, 2019.
3. ↑ ^{a b} Entry on α-naphtholphthalein. In: Römpp Online . Georg Thieme Verlag, accessed on September 16, 2011.