Internal rotation of the OH group in di-anils of 2-hydroxy-5-methyl-isophthaldehyde

H-1, C-13 and N-15 NMR spectra of di-R-anils of 2-hydroxy-5-methyl-isophthaldehyde (R=H, CH3, OCH3) were recorded in CDCl3 solution and the spectral assignments were performed. The variable temperature measurements over the range 310-223 K show evidence of a slowing down of the internal rotation of the OH group in comparison with the rotation of the free OH group in phenols. The kinetic parameters of the OH group rotation in the di-anils were determined by means of 1H NMR lineshape analysis. The conformational changes in molecules are discussed. (C) 1997 Elsevier Science B.V.