Infrared and nuclear magnetic resonance spectroscopic study of secondary amide hydrogen bonding in benzoyl PABA derivatives (retinoids)

Appl Spectrosc. 2007 Jun;61(6):603-7. doi: 10.1366/000370207781269774.

Abstract

Attenuated total reflection (ATR) Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) data are used to characterize the hydrogen bonding of the secondary amide N-H group of several structurally similar benzoyl derivatives of p-aminobenzoic acid esters (retinoids) in chloroform solution. The amide N-H can form intermolecular hydrogen bonds to several proton acceptors in these molecules or it can form an intramolecular hydrogen bond to a fluorine or oxygen atom in some of the molecules. The concentration dependence of the solution N-H infrared absorption bands is used to determine the formation of intramolecular and/or intermolecular H-bonds. Proton NMR spectra were obtained from deuterated chloroform solutions and the sec-amide N-H resonance was assigned for each compound. The downfield shift in the N-H resonance is correlated to intramolecular H-bond formation. Also, the NMR spectra of fluorine-containing compounds provide J(F-H) through-space coupling values. Using infrared and NMR data, the relative intramolecular hydrogen bond strengths (N-H...F or N-H...O) of the compounds are approximately ranked.

Publication types

  • Evaluation Study

MeSH terms

  • Amides / chemistry*
  • Hydrogen Bonding
  • Magnetic Resonance Spectroscopy / methods*
  • Retinoids / chemistry*
  • Spectroscopy, Fourier Transform Infrared / methods*
  • para-Aminobenzoates*

Substances

  • Amides
  • Retinoids
  • para-Aminobenzoates