Halogenation and amination dual properties of haloamines in Raschig environment: A chlorine transfer reaction between chloramine and 3-azabicyclo[3,3,0]octane
✍ Scribed by M. Elkhatib; A. Marchand; L. Peyrot; J. J. Counioux; H. Delalu
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 142 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0538-8066
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✦ Synopsis
The chlorine transfer reaction between 3-azabicyclo 0]octane "AZA" and chloramine was studied over pH 8 -13 in order to follow both the amination and halogenation properties of NH 2 Cl. The results show the existence of two competitive reactions which lead to the simultaneous formation of N-amino-and N-chloro-3-azabicyclo[3,3,0]octane by bimolecular kinetics. The halogenation reaction is reversible and the chlorine derivative obtained, which is thermolabile and unstable in the pure state, was identified by electrospray mass spectrometry. These phenomena were quantified by a reaction between neutral species according to an apparent S N 2-type mechanism for the amination process and a ionic mechanism involving a reaction between chloramine and protonated amine for the halogenation process. Amination occurs only in strongly basic solutions (pH Ն 13) while chlorination occurs at lower pH's (pH Յ 8). At intermediate pH's, a mixture of these two compounds is obtained. The relative proportions of the products are a function of intrinsic rate constants, pH and pK a of the reactants. The rate constants and thermodynamic activation parameters are the following: k 1 ϭ 45.5 ϫ 10 Ϫ3 M Ϫ1 s Ϫ1 ; ⌬H 1 0# ϭ 59.8 kJ mol Ϫ1 ; ⌬S 1 0# ϭ Ϫ 86.5 J mol Ϫ1 K Ϫ1 for amination; k 2 ϭ 114 ϫ 10 Ϫ3 M Ϫ1 s Ϫ1 ; ⌬H 2 0# ϭ 63.9 kJ mol Ϫ1 ; and ⌬S 2 0# ϭ Ϫ 48.3 J mol Ϫ1 K Ϫ1 for chlorination. The ability of an interaction corresponding to a specific (NH 3 Cl ϩ /RRЈNH) or general (NH 2 Cl/RRЈNH) acid catalysis has been also discussed.