145-50-6

Basic information

• Product Name: p-Naphtholbenzein
• Synonyms: α-Naphtholbenzein,4,4′-(α-Hydroxybenzylidene)di-1-naphthol, p-naphtholbenzein;alpha-Naphtholbenzein, pure, 90% 10GR;alpha-Naphtholbenzein, pure, 90% 25GR;1-NAPHTHOLBENZEIN INDICATOR 5 G;α- naphthol quinone phenylMethane;MAG BIND EQUIPURE GDNA (1X96);1-Naphtholbenzein indicator Reag. Ph Eur;LABOTEST-BB LT00452038
• CAS NO: 145-50-6
• Molecular Formula: C₂₇H₁₈O₂
• Molecular Weight: 374.43
• EINECS: 230-116-9
• Product Categories: Analytical Chemistry;Indicator (pH);pH Indicators;Benzein
• Mol File: 145-50-6.mol
• Article Data: 3

Chemical Properties

• Melting Point: 230-235 °C(lit.)
• Boiling Point: 463.44°C (rough estimate)
• Flash Point: 242.337 °C
• Appearance: Pale Red-Brown/Liquid
• Density: 1.0946 (rough estimate)
• Vapor Density: 12.9 (vs air)
• Vapor Pressure: 5.48E-14mmHg at 25°C
• Refractive Index: 1.4875 (estimate)
• Storage Temp.: Store at +5°C to +30°C.
• Solubility: Solubility Insoluble in water; soluble in ethanol, methanol
• PKA: 8.95(at 25℃)
• Water Solubility: insoluble
• Stability: Stable. Combustible. Incompatible with strong oxidizing agents.
• BRN: 3471575
• CAS DataBase Reference: p-Naphtholbenzein(CAS DataBase Reference)
• NIST Chemistry Reference: p-Naphtholbenzein(145-50-6)
• EPA Substance Registry System: p-Naphtholbenzein(145-50-6)

Safety Data

• Hazard Codes: Xi
• Statements: 36/37/38
• Safety Statements: 26-36-37/39
• WGK Germany: 3
• F: 10-21
• TSCA: Yes
• Hazardous Substances Data: 145-50-6(Hazardous Substances Data)

Usage

Chemical Properties

deep red to rust-coloured crystals

Uses

alpha-Naphtholbenzein is a pH indicator (pH 0.0-0.8/ pH 8.2-10.0). Dyes and metabolites.

InChI:InChI=1/C27H18O2/c28-25-16-14-23(19-10-4-6-12-21(19)25)27(18-8-2-1-3-9-18)24-15-17-26(29)22-13-7-5-11-20(22)24/h1-17,28H/b27-24-

Synthetic route

α-naphthol (90-15-3) + Benzotrichlorid (98-07-7) → (E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon (145-50-6)

Conditions	Yield
for 0.166667h; Heating;	34%

α-naphthol (90-15-3) + Benzotrichlorid (98-07-7) → (E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon (145-50-6) + 5-oxo-14-phenyl-5H-dibenzoxanthene

Conditions	Yield
for 0.166667h; Heating;	A n/a B 10.5%
for 0.166667h; Heating;

α-naphthol (90-15-3) + 2-methoxy-phenol (90-05-1) + Benzotrichlorid (98-07-7) → 4-(4-hydroxy-3-methoxy-benzhydrylidene)-2-methoxy-cyclohexa-2,5-dienone (55252-36-3) + (E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon (145-50-6) + 4-[1-(4-Hydroxy-3-methoxy-phenyl)-1-phenyl-meth-(E)-ylidene]-4H-naphthalen-1-one

Conditions	Yield
With aluminium trichloride for 0.166667h; Heating;	A n/a B n/a C 4.8%

α-naphthol (90-15-3) + ortho-cresol (95-48-7) + Benzotrichlorid (98-07-7) → 4-(4-hydroxy-3-methyl-benzhydrylidene)-2-methyl-cyclohexa-2,5-dienone (5664-07-3) + (E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon (145-50-6) + 4-[1-(4-Hydroxy-3-methyl-phenyl)-1-phenyl-meth-(E)-ylidene]-4H-naphthalen-1-one

Conditions	Yield
for 0.166667h; Heating;	A n/a B n/a C 3.8%

α-naphthol (90-15-3) + benzene-1,2-diol (120-80-9) + Benzotrichlorid (98-07-7) → (E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon (145-50-6) + 4-[1-(3,4-Dihydroxy-phenyl)-1-phenyl-meth-(Z)-ylidene]-2-hydroxy-cyclohexa-2,5-dienone + 4-[1-(3,4-Dihydroxy-phenyl)-1-phenyl-meth-(E)-ylidene]-4H-naphthalen-1-one

Conditions	Yield
for 0.166667h; Heating;	A n/a B n/a C 3.2%

o-Hydroxyethylbenzene (90-00-6) + α-naphthol (90-15-3) + Benzotrichlorid (98-07-7) → (E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon (145-50-6) + 2-Ethyl-4-[1-(3-ethyl-4-hydroxy-phenyl)-1-phenyl-meth-(Z)-ylidene]-cyclohexa-2,5-dienone + 4-[1-(3-Ethyl-4-hydroxy-phenyl)-1-phenyl-meth-(E)-ylidene]-4H-naphthalen-1-one

Conditions	Yield
for 0.166667h; Heating;	A n/a B n/a C 1.8%

α-naphthol (90-15-3) + 2-hydroxybromobenzene (95-56-7) + Benzotrichlorid (98-07-7) → (E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon (145-50-6) + 2-Bromo-4-[1-(3-bromo-4-hydroxy-phenyl)-1-phenyl-meth-(Z)-ylidene]-cyclohexa-2,5-dienone + 4-[1-(3-Bromo-4-hydroxy-phenyl)-1-phenyl-meth-(E)-ylidene]-4H-naphthalen-1-one

Conditions	Yield
With aluminium trichloride for 0.166667h; Heating;	A n/a B n/a C 1.8%

5-propylphenol (644-35-9) + α-naphthol (90-15-3) + Benzotrichlorid (98-07-7) → (E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon (145-50-6) + 4-[1-(4-Hydroxy-3-propyl-phenyl)-1-phenyl-meth-(Z)-ylidene]-2-propyl-cyclohexa-2,5-dienone + 4-[1-(4-Hydroxy-3-propyl-phenyl)-1-phenyl-meth-(E)-ylidene]-4H-naphthalen-1-one

Conditions	Yield
With aluminium trichloride for 0.166667h; Heating;	A n/a B n/a C 1.5%

α-naphthol (90-15-3) + Benzotrichlorid (98-07-7) + phenol (108-95-2) → benzaurine (569-60-8) + (E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon (145-50-6) + 4-[1-(4-Hydroxy-phenyl)-1-phenyl-meth-(E)-ylidene]-4H-naphthalen-1-one

Conditions	Yield
for 0.166667h; Heating;	A n/a B n/a C 1.5%

(E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon (145-50-6) → bis(4-hydroxy-1-naphtyl)phenylmethane (84148-54-9)

Conditions	Yield
With sodium tetrahydroborate In ethanol	95.2%
With reducing reagent Yield given;

(E/Z)-4-<(4-Hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon (145-50-6) → (E/Z)-2-Brom-4-<(3-brom-4-hydroxy-1-naphthyl)phenylmethylen>-1(4H)-naphthalinon

Conditions	Yield
With bromine In chloroform for 24h; Ambient temperature;	82%

Upstream product

• 90-15-3 α-naphthol 
• 98-07-7 Benzotrichlorid 
• 95-48-7 ortho-cresol 
• 108-95-2 phenol 
• 95-56-7 2-hydroxybromobenzene 
• 644-35-9 5-propylphenol 
• 90-00-6 o-Hydroxyethylbenzene 
• 90-05-1 2-methoxy-phenol 
• 120-80-9 benzene-1,2-diol 

Downstream Products

• 1620197-94-5 (Z)-4-((5-((4-oxonaphthalen-1(4H)-ylidene)(phenyl)methyl)naphthalen-1-yl)oxy)phthalonitrile 
• 84148-54-9 bis(4-hydroxy-1-naphtyl)phenylmethane 

Relevant articles and documents

Phenol-naphthol-benzeine - Synthesis and chromophoric properties. Part 5: Benzeines

Phenols 4 and 1-naphthol (5) react with benzotrichloride (6) to give benzaurines 7, phenol-naphthol-benzeines 3 and α-naphtholbenzein (1), which were isolated by chromatography. Phenol-naphthol-benzeines 3 are X-/Y-chromophores like α-naphtholbenzeine (1) with two absorption maxima. These are hypsochromically shifted in neutral, in alkaline and in acidic solution, compared with those of 1.

5-Oxo-14-phenyl-5H-dibenzo[a,h]xanthene - Part of the indicator 'α-naphtholbenzein'

The indicator substance α-naphtholbenzein 1/2 is synthesized from 1-naphthol and benzotrichloride. This reaction gives always 5-oxo-14-phenyl-5H-dibenzo[a,h]xanthene (3), too. 3 shows an orange color, which is pH-independent, and an orange fluorescence. Subsequently, the formation of 3 is investigated.