ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

On the tautomerism of 1-phenyl-3-substituted-pyrazol-5-ones and their photoinduced products — experimental and theoretical UV spectral analysis

Atanas G. Chapkanov, Bojidarka B. Koleva, Michail G. Arnaudov, and Ivan K. Petkov

Department of Chemistry, South-West University Neofit Rilski, 66 I. Mihailov str., 2700 Blagoevgrad, Bulgaria

E-mail: nasko50@yahoo.com

Received: 7 June 2007  Revised: 12 September 2007  Accepted: 17 September 2007

Abstract: A detailed experimental and theoretical UV-spectral analysis of the tautomeric forms of 3-methyl-1-phenyl pyrazol-5-one and 1,3-diphenyl pyrazol-5-one as well as of the UV-irradiated photoinduced products of the latter compound were carried out. The experimental UV-spectra were compared with the theoretical ones obtained by CIS/6-31G**. Selected geometrical parameters of the different tautomers were estimated by ab initio calculations using the RHF/6-31G** level of theory and basis set, which have also been discussed with a view to the corresponding UV-results.

Keywords: pyrazol-5-ones tautomerism - UV-spectra - theoretical analysis - photoisomerization

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-008-0026-y

Chemical Papers 62 (3) 294–301 (2008)