4-Hydroxy-1-naphthaldehydes: proton transfer or deprotonation

Y Manolova, V Kurteva , L Antonov, H Marciniak , S Lochbrunner, A Crochet , K.M. Fromm, Fadhil S. Kamounah, Poul Erik Hansen

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A series of naphthaldehydes, including a Mannich base, have been investigated by UV-Vis spectroscopy, NMR and theoretical methods to explore their potential tautomerism. In the case of 4-hydroxy-1-naphthaldehyde concentration dependent deprotonation has been detected in methanol and acetonitrile. For 4-hydroxy-3-(piperidin-1-ylmethyl)-1-naphthaldehyde (a Mannich base) an intramolecular proton transfer involving the OH group and the piperidine nitrogen occurs. In acetonitrile the equilibrium is predominantly at the OH-form, whereas in methanol the proton transferred tautomer is the preferred form. In chloroform and toluene, the OH form is completely dominant. Both 4-hydroxy-1-naphthaldehyde and 4-methoxy-1-naphthaldehyde (fixed enol form) show dimerization in the investigated solvents and the crystallographic data, obtained for the latter, confirm the existence of a cyclic dimer
Original languageEnglish
JournalPhysical Chemistry Chemical Physics
Issue number15
Pages (from-to)10238-49
Number of pages12
Publication statusPublished - 2015


  • proton transfer
  • Mannich base
  • dimerization
  • DFT calculations

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