Prototropic processes in benzaurins. 19F and 1H NMR spectra of fluoro- and methylsubstituted 4-hydroxyphenyl-diphenylcarbinols, related fuchsones and benzaurins

• Authors: Poul Hansen , Alexsander Peregudov , Dimitrii Kravtsov , Antonina Krylova , Galina Babakhina , Ludmila Golovchenko , Valentina Pachevskaya
• Languages of publication: EN

Abstracts

EN

Tautomerism of benzaurins and hydration are studied. 1H and 19F chemical shifts have been determined for a number of substituted 4-hydroxyphenyl-diphenyl carbinols containing fluorine in a 3-, 3*- or 4*-position, and for similar compounds containing additional methyl groups in a position of 3, 3** or 4**. The same data have been obtained for the fuchsones prepared by dehydration of the above carbinols. On this basis chemical shifts of fluorine in different positions have been evaluated as a monitor of the transformation of 4-hydroxyphenyl group to the semiquinone moiety. The 19F NMR can be used to monitor the transformation of 4**-fluorobenzaurin and the related 3,3*-disubstituted and 3,3*,5,5*-tetramethylsubstituted compounds to the corresponding carbinols due to the addition of a water molecule and to study the tautomerism of the two latter benzaurins as well as that of 3,3*,4**trifluorobenzaurin. Furthermore, fluorine and methyl group chemical shifts are sensitive to syn-anti-isomerism in substituted fuchsones.The prototropic process of these compounds may be slow or fast on a 1H NMR time scale depending on the solvent and may be catalyzed by water or carbonic acids. On the basis of kinetic and thermodynamic data obtained by dynamic NMR studies, a mechanism for the process has been proposed.

Keywords

EN

19F NMR; Prototropic tautomerism; Syn-anti isomerism; Fluoro- and methyl substituted benzaurins; Fuchsones

• Publisher: De Gruyter Open
• Journal: Open Chemistry
• Year: 2011
• Volume: 9
• Issue: 2
• Pages: 253-264

Dates

published

1 - 4 - 2011

online

17 - 2 - 2011

Contributors

author

Poul Hansen

• Roskilde University

author

Alexsander Peregudov

• Russian Academy of Science

author

Dimitrii Kravtsov

• Russian Academy of Science

author

Antonina Krylova

• Russian Academy of Science

author

Galina Babakhina

• Russian Academy of Science

author

Ludmila Golovchenko

• Russian Academy of Science

author

Valentina Pachevskaya

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Identifiers

DOI

10.2478/s11532-011-0003-0