Chemical-shift link to the Kamlet–Taft β parameter

In investigating liquid-phase proton NMR spectra of 2,2-dimethyl-1-(2,4,6-trinitrophenyl)hydrazine in various solvents, we have found an interesting correlation, at sufficiently low temperatures T, between the chemical-shift difference (splitting) of the picryl proton peaks, measured as f(T), and th...

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Bibliographic Details
Published inCanadian journal of chemistry Vol. 82; no. 12; pp. 1707 - 1711
Main Authors Brown, Keith C, El-Bermani, Muhsin, Weil, John A
Format Journal Article
LanguageEnglish
Published Ottawa, Canada NRC Research Press 01.12.2004
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Summary:In investigating liquid-phase proton NMR spectra of 2,2-dimethyl-1-(2,4,6-trinitrophenyl)hydrazine in various solvents, we have found an interesting correlation, at sufficiently low temperatures T, between the chemical-shift difference (splitting) of the picryl proton peaks, measured as f(T), and the Kamlet–Taft hydrogen-bonding basicity parameter β. The observed solvolytic effect offers a convenient way of determining and checking the value of the empirical parameter β. The phenomenon discloses that the molecular geometric configuration is affected vividly by hydrogen bonding with the surrounding solvent molecules. It follows that the internal conformation interchange taking place (in a higher T range) is not in fact solely a unimolecular property.Key words: picryl proton NMR, chemical shift, solvent effects, hydrogen bonding, Kamlet–Taft β.
ISSN:0008-4042
1480-3291
DOI:10.1139/v04-149