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Updated: May 8, 2026

Facile Preparation of 4-Substituted Quinazoline Derivatives

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Published on: February 15, 2016

7-Hydroxyquinoline-8-carbaldehydes. 2. Prototropic equilibria.

Volha Vetokhina¹, Jacek Nowacki, Mariusz Pietrzak

¹Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.

The Journal of Physical Chemistry. A

|August 23, 2013

Summary

This study investigates 7-hydroxyquinoline-8-carbaldehydes (7-HQCs) in aqueous solutions, revealing their complex prototropic equilibria and photophysical properties influenced by tautomerization and protonation states.

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Published on: June 10, 2021

Area of Science:

Photochemistry
Physical Organic Chemistry
Spectroscopy

Background:

7-hydroxyquinoline-8-carbaldehydes (7-HQCs) are trifunctional proton-donating/accepting systems.
Understanding their behavior in aqueous solutions is crucial for their application.

Purpose of the Study:

To elucidate the prototropic equilibria of 7-HQCs in aqueous solutions.
To characterize the electronic absorption and fluorescence properties of their various forms.
To rationalize these properties based on tautomerization and protonation processes.

Main Methods:

(1)H NMR spectroscopy
Photostationary and time-resolved UV-vis spectroscopy
Quantum chemical computations (ab initio)

Main Results:

Identified four main neutral and ionic structures: 7-quinolinol (OH), 7(1H)-quinolinone (NH), deprotonated anion (A), and protonated cation (C).
Rationalized electronic absorption and fluorescence based on ground and excited-state tautomerization, protonation, and deprotonation.
Compared photophysical properties of 7-HQCs with their precursors, 7-hydroxyquinolines (7-HQs).

Conclusions:

Prototropic equilibria and photophysical properties of 7-HQCs are complex, involving multiple species.
Spectroscopic and computational methods successfully elucidated these behaviors.
Findings provide insights into the photochemistry of related quinoline systems.