Acid catalytic effects in the chlorination of propanoic acid

Tapio Salmi*, Päivi Mäki-Arvela, Erkki Paatero, Rune Byggningsbacka

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)

Abstract

Selective α-chlorination of propanoic acid to form 2-monochloropropanoic (MCA) and 2,2-dichloropropanoic acid (DCA) was investigated in a laboratory-scale, semibatch reactor at 90-130°C at atmospheric total pressure and in the presence of chlorosulfonic acid (CISO3H) and 2,2-dichloroethanoic acid (DCA') as catalytic agents and oxygen as a radical scavenger. The decomposition of the catalyst was investigated with sulfur analysis and UV-spectrometry. The studies revealed that the majority of sulfur remains in the reaction mixture, but is converted to an inactive form during the chlorination. The reasons may be the decomposition of CISO3H and its reaction with propanoic acid. The kinetic experiments revealed autocatalytic and parallel formation of MCA and DCA, the selectivity being independent of Cl2 concentration in the liquid phase. The experiments with DCA' also demonstrated that DCA' has a catalytic effect on the chlorination. The experiments confirmed the validity of a previously proposed reaction scheme for α-chlorination, which comprises the formation of the reaction intermediate (propanoyl chloride) from propanoic acid and CISO3H, the acid-catalyzed enolization of the acid and a hydroxyl-chlorine exchange reaction. The acid-catalyzed enolization is the rate determining step in the reaction sequence. The kinetic data were fitted to rate equations based on the reaction scheme. (C) 2000 Society of Chemical Industry.

Original languageEnglish
Pages (from-to)89-97
Number of pages9
JournalJournal of Chemical Technology and Biotechnology
Volume75
Issue number1
DOIs
Publication statusPublished - Jan 2000
MoE publication typeA1 Journal article-refereed

Keywords

  • Acid catalysis
  • Chlorination
  • Chlorosulfonic acid catalyst
  • Propanoic acid

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