Related Experiment Video
Updated: Jun 22, 2026

Facile Preparation of 4-Substituted Quinazoline Derivatives
Published on: February 15, 2016
Structure dependent prototropy in 4-hydroxy-3-formylideneamino-1-methyl/phenylquinolin-2-ones
T Sheshashena Reddy1, N Rameshwar, B Bhudevi
1Department of Chemistry, University College of Science, Osmania University Campus, Osmania University, Hyderabad 500007, Andhra Pradesh, India.
Abstract:
The electronic absorption spectra of 4-hydroxy-3-formyl quinolin-2-ones and their Schiff bases were investigated in various solvents of varying polarity. The three aromatic transitions of napthalene in quinolin-2-one are shifted to longer wavelength on their transformation to anils. Electron-donating group in the anils lead to enolimine form, while electron-withdrawing group leads to an equilibrium mixture of enolimine and ketoamine forms and the Schiff base derived from alkyl amine exist in ketoamine form. The prototropic interconversion of enolimine and ketoimine forms in the anils with the electron-withdrawing substituted anils is further supported by proton NMR studies. The spectral shifts are solvent dependent. Dipolar aprotic solvents bring bathochromic shift while polar protic solvents cause blue shift in the longer wavelength absorption maxima. In the case of Schiff bases substituted by electron-donating group the bathochromic shift is directly related to the polarity of the solvents.
Related Concept Videos
Prochirality
Chirality at Nitrogen, Phosphorus, and Sulfur
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
Structure of Amines
Woodward–Hoffmann Selection Rules and Microscopic Reversibility
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
![Solid-phase Synthesis of [4.4] Spirocyclic Oximes](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F58508.jpg&w=3840&q=50)
![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg&w=3840&q=50)