Naphtholphthalein
Structural formula | ||||||||||||||||
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General | ||||||||||||||||
Surname | Naphtholphthalein | |||||||||||||||
other names |
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Molecular formula | C 28 H 18 O 4 | |||||||||||||||
Brief description |
light brown or beige powder |
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properties | ||||||||||||||||
Molar mass | 418.44 g mol −1 | |||||||||||||||
Physical state |
firmly |
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Melting point |
253-255 ° C |
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solubility |
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safety instructions | ||||||||||||||||
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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
- ↑ a b Data sheet naphtholphthalein from Sigma-Aldrich , accessed on December 25, 2019 ( PDF ).
- ↑ a b c d Data sheet naphtholphthalein (PDF) from Merck , accessed on December 25, 2019.
- ↑ a b Entry on α-naphtholphthalein. In: Römpp Online . Georg Thieme Verlag, accessed on September 16, 2011.