Solvatochromic Behaviour and Prototropic Studies of some oxazolones of electron donor‐acceptor type

Abstract

Solvatochromic and halochromic behaviour in the u.v.‐vis absorption spectra of some substituted 4‐arylidene‐2‐aryloxazol‐5‐ones (1–5) are studied. Positive and negative solvatochromism, depending on the substituent present, are observed in different hydrogen bonding donoracceptor (HBD‐A) and hydrogen bonding acceptor (HBA) solvents. However, in non hydrogen bonding (NHB) solvents all compounds show a positive solvatochromism. A considerable intramolecular charge transfer interaction, between the donor and acceptor parts in the oxazolones studied, is observed. Small fluorescence quantum yields are observed for the oxazolones. In triethanolamine‐acetone mixtures, the visible absorption spectra of the hydroxy substituted oxazolone shows an additional long‐wavelength band suggesting the existance of prototropic equilibria. The prototropic equilibrium constants at different temperatures are determined.

Physical characteristics and polarographic reduction mechanism of some oxazolones

“…This can be attributed to a change in the concentration of the electroactive species near the electrode surface with time. Such a change may be caused by hydrolysis of the oxazolones being catalysed by the alkali to form the corresponding acid (3,9,10,15).…”

“…Oxazolones (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) were prepared according to recommended procedure (13). The purity and structures of the compounds were checked by measurements of mp, nmr, mass spectra, and elemental analysis.…”

“…On the other hand, the polarographic behaviour of the oxazole ring, structurally a heterocyclic system, has attracted only minor attention in literature (3, 4) as compared to major spectroscopic investigations (5)(6)(7)(8)(9)(10). Consequently, in the present investigation our attention was devoted mainly to oxazolones possessing wide applications in the electrosyntheses of various amino alcohols, thiamine, and amino acids (11,12).…”

“…Consequently, in the present investigation our attention was devoted mainly to oxazolones possessing wide applications in the electrosyntheses of various amino alcohols, thiamine, and amino acids (11,12). The study was focussed on the polarographic behaviour of some oxazolones (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15), in Thiel buffer -ethanolic solutions of different pH values as well as in DMF. The electrode reaction mechanism and various physical properties of these compounds were also investigated.…”