Ten para- and meta-substituted 2-phenyl-4,4-dimethyloxazolidines I (R = MeO, halo, NO2, NMe2) have been synthesized and their tautomeric equilibrium with the corresponding Schiff bases studied by NMR in chloroform, acetone and DMSO. Fairly good linear free energy relationships were found to be present between the equilibrium constant, K, and the substituent constant s+, Of the substituent, indicating a pos. charged intermediate may be involved in the equilibrium The chem. shift, d, of the 2-proton of the oxazolidines is also correlated linearly with the Hammett s of the substituent. The slopes of both the log J/K0-s+ and the d-s-lines are dependent on the solvent polarity.

Key words: NMR SPECTROMETRY, CHLOROFORM, DMSO, ACETONE, EQUILIBRIUM CONSTANT, SOLVENT EFFECT, CHEMICAL SHIFT, TAUTOMERISM, SUBSTITUENT EFFECT, SCHIFF BASE