Theoretical problems associated with the use of acetic anhydride as a co-solvent for the non-aqueous titration of hydrohalides of organic bases and quaternary ammonium salts

Gergely Völgyi, Szabolcs Béni, Krisztina Takács-Novák, Sándor Görög

Research output: Contribution to journalArticle

Abstract

A potentiometric titration study of organic base hydrohalides and quaternary ammonium salts using perchloric acid as the titrant and a mixture of acetic anhydride and acetic acid as the solvent was carried out and the titration mixture was analysed by NMR in order to clarify the chemistry of the reactions involved. It was found that in contrast to the general belief the formation of acetyl halides and titratable free acetate ion does not take place prior to the titration but NMR spectra proved the formation of acetyl halides in the course of the titration. This observation and the fact that the shape of the titration curves depends on the nature of the hydrohaloic acid bound to the base or of the anion in the quaternary ammonium salts led to the conclusion that the titrating agent is acetyl perchlorate formed in situ during the titration. Equations of the reactions involved in the titration process are shown in the paper.

Original languageEnglish
Pages (from-to)18-23
Number of pages6
JournalJournal of Pharmaceutical and Biomedical Analysis
Volume51
Issue number1
DOIs
Publication statusPublished - Jan 5 2010

Keywords

  • Acetic anhydride
  • Hydrohaloid salts
  • Non-aqueous titration
  • Potentiometry
  • Quaternary ammonium salts

ASJC Scopus subject areas

  • Analytical Chemistry
  • Pharmaceutical Science
  • Drug Discovery
  • Spectroscopy
  • Clinical Biochemistry

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