Mechanism of dansylation of the polyamine pentaazapentacosane ·5 HCl

Susan Heimbecher, Yung Chi Lee, S. Esmail Tabibi, Samuel H. Yalkowsky

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1 Scopus citations


Dansylation of the pentaamine pentaazapentacosane ·5 HCl (PAPC) produces only the perdansyl product. This occurs even under conditions of pH and dansyl chloride concentration most likely to produce partially dansylated products. This result is explained by a mechanism whereby only completely unionized amine molecules will dansylate. The proposed mechanism is supported by the dansylation versus pH profile of PAPC versus that of a reference monoamine (piperidine ·HCl). After 4 h at room temperature and pH 9.5, 100% of piperidine is dansylated while under the same conditions only 10% of PAPC is derivatized. A pH greater than 10.5 is required to completely dansylate PAPC. This difference is significantly greater than would be predicted from the pK(a) values but it is consistent with the proposed mechanism.

Original languageEnglish (US)
Pages (from-to)21-29
Number of pages9
JournalInternational Journal of Pharmaceutics
Issue number1
StatePublished - Jan 12 1998


  • Dansyl chloride
  • Dansylation
  • Pentaazapentacosane pentahydrochloride
  • Polyamines

ASJC Scopus subject areas

  • Pharmaceutical Science


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