Solvent effects on the absorption spectrum of the product and the equilibrium constant for the proton transfer reaction from 1-phenacylquinolinium bromide to amines

Takeshi Matsumoto, Yoshimi Sueishi, Shunzo Yamamoto

Research output: Contribution to journalArticle

Abstract

The equilibrium constants, K2, have been determined for the proton-transfer reactions of 1-phenacylquinolinium ion, PHQ+, with several amines {triethylamine (TEA), N,N,N′,N′- tetramethylethylenediamine (ED), N,N,N′,N′-tetramethylpropanediamine (PD), N,N,N′,N′-tetramethylbutanediamine (BD), and 1,8-bis(dimethylamino-naphthalene (DMAN)} in acetonitrile (AN), AN-tetrahydrofuran (THF) and AN-ethanol (EtOH) mixtures. The reaction was followed spectrophotometrically using a stopped-flow technique. The K 2 value decreased for DMAN and increased for TEA with increasing vol-% of THF in AN-THF mixtures. The changes in the K2 value for ED, PD and BD changed in the order: ED, PD and BD from a pattern similar to TEA to a pattern similar to DMAN. The change in the K2 value for DMAN with increasing vol-% of THF in AN-THF mixtures was explained by the effect of polarity on the stability of P-Q+ (the deprotonated product of PHQ+). The effect of THF on the K2 value is consistent with that of the peak wavelength of the absorption spectrum of P -Q+. The change in the K2 value for TEA, ED, PD and BD depended on the structures of the protonated bases, one of the products for this reaction. The effect of EtOH on the K2 value for DMAN was examined in ternary EtOH-THF-AN mixtures that contain different amounts of EtOH and whose relative permittivities were adjusted to that of EtOH. The K 2 value increased with increasing vol-% of EtOH because of the stabilization of P-Q+ upon the formation of the hydrogen-bonded complex with EtOH. The absorption spectrum of P -Q+ demonstrated a blue shift as the vol-% of EtOH increased.

Original languageEnglish
Pages (from-to)275-285
Number of pages11
JournalJournal of Solution Chemistry
Volume36
Issue number2
DOIs
Publication statusPublished - Feb 1 2007

Keywords

  • Hydrogen-bonding
  • Polar effect
  • Proton transfer reaction
  • Solvent effect

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Physical and Theoretical Chemistry

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