Global Electrophilicity Study of the Reaction of Pyrroles with N-Halo Compounds and the Rate-Determining Step


  •  Michael De Rosa    
  •  Hae-Won Kim    

Abstract

Pyrroles (nucleophiles) can react with N-halo compounds (electrophiles) to give either addition-elimination or halogenation products. Global electrophilicity (w) has been used to study electrophile-nucleophile combinations. The w values of the N-halo compounds (n = 22) used were calculated using DFT/B3LYP. No correlation was observed between w and the pathway of reaction/non-reaction. A single parameter (w) could not explain the results of the competing reactions that are taking place in this system–reactions that appear to depend on the N-halogen (Cl, Br, I) nucleophilicity/basicity and possibly hardness of the leaving group. These calculations confirmed that the rate-determining step of the addition-elimination process was not the formation of an sigma-complex, but its subsequent reaction. Calculations suggested that deprotonation of the sigma-complex was the rate-determining step in the halogenation reactions. It was also possible to examine the effects of the structure of the N-halo-compound and the halogen.



This work is licensed under a Creative Commons Attribution 4.0 License.
  • ISSN(Print): 1916-9698
  • ISSN(Online): 1916-9701
  • Started: 2009
  • Frequency: semiannual

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