Untersuchungen zum UV/Vis-Spektralverhalten von Azofarbstoffen. VI. Zum Einfluß von Substituenten auf die Farbe von Derivaten des 1-Phenylazo-2-naphthols

✍ Scribed by Dipl.-Chem. H. Mustroph; Dipl.-Chem. R. Bartel

• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 409 KB
• Volume: 324
• Category: Article
• ISSN: 1615-4150
• DOI: 10.1002/prac.19823240507

✦ Synopsis

Studies on UV/Vis Absorption Spectra of Azo Dyes. VI. The Effect of Substituents on the Color of Derivatives of 1‐Phenylazo‐2‐naphthols

The absorption spectrum of 1‐(4′‐diethylaminophenylazo)‐2‐naphthol has been examined, and it has been found that the absorption band at 510 nm corresponds to the azo form and the shoulder at 610 nm corresponds to the hydrazone tautomeric form. Substituents in 3‐position of 2‐naphthol which have a free proton (e.g. OH, COOH, CONHR) stabilize the hydrazone tautomeric form by an intramolecular hydrogen bonding between substituent and hydrazone oxygen. Substituents which have not a free proton (e.g. OCH~3~, COOCH~3~, CONR~1~R~2~) have little influence on the absorption spectrum.

The relative intensities of the two bands of the tautomeric forms are dependent on:
— the electron attracting or electron releasing effect of the substituent R in CONHR

— the hydrogen bonding acidity of the substituents in 2′‐position if R in CONHR is a phenylring

— the hydrogen bonding acidity of the solvent.

The effect of substituents in the phenylazo subsystem is also discussed.