NMR study of proton transfer equilibrium in Schiff bases derived from 2-hydroxy-1-naphthaldehyde and 1-hydroxy-2-acetonaphthone. Deuterium isotope effects on13C and15N chemical shifts

Abstract

The proton transfer equilibrium in series of Schiff bases derived from 2-hydroxy-1-naphthaldehyde and 1-hydroxy-2-acetonaphthone were measured by means of 1 H, 13 C and 15 N NMR spectra and deuterium isotope effects on 13

Synthesis of Some New Anils: Part 1. Reaction of 2-Hydroxy-benzaldehyde and 2-Hydroxynaphthaldehyde with 2-Aminopyridene and 2-Aminopyrazine

“…2-Hydroxy Schiff base ligands are of interest mainly due to the existence of (O-H···N and N-H···O) type hydrogen bonds and tautomerism between the enol-imine and keto-enamine forms (Scheme 1). Tautomerism in 2-hydroxy Schiff bases both in solution and in the solid state was investigated using different spectroscopic techniques [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. In the spectra of solutions of these compounds different Schiff bases have been studied in both polar and non-polar solvents [5,6,8,9,11,13,16,20].…”

“…In the solid state, salicylideneanilines exist mostly in the enol-imino tautomeric form. In naphthaldimines both forms are possible and O-H···N or N-H···O intramolecular hydrogen bonds can occur [2,3,14,19,22]. The hydrogen bonding and tautomerism of Schiff bases and the tautomeric forms at 50% abundance have been reported in the crystalline state for the Schiff base formed by 3-haloanilines and 2-hydroxy-1-naphthaldehyde [3].…”

Chiral recognition of the Schiff bases by NMR spectroscopy in the presence of a chiral dirhodium complex. Deuterium isotope effect on 13C chemical shift of the optically active Schiff bases and their dirhodium adducts

“…racemic 2-aminobutane or˛-methyl-benzylamine according to the procedure described elsewhere. 20,21 The synthesis of dirhodium tetrakis[(R)-˛-methoxy-˛-(trifluoromethyl)-phenylacetate] has been reported earlier. 14 The 1 H and 13 C NMR spectra in CDCl 3 were recorded on a BRUKER DPX-400 spectrometer operating at 400.…”

Isotope effect on chemical shifts in hydrogen‐bonded systems

“…21,22,60,64 It was shown earlier that 1 DN(D) depended on the mole fraction. 65 The idea of dividing isotopes effects into intrinsic and equilibrium isotopes has been tested in o-hydroxy Schiff bases.…”