Chemical-shift link to the KamletTaft 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 the KamletTaft 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, KamletTaft β.
The development of an NMR chemical shift prediction application with the accuracy necessary to grade proton NMR spectra for identity