Homolytic NBr bond dissociation constitutes the initial step of numerous reactions involving N-brominated species. However, little is known about the strength of NBr bonds toward homolytic cleavage. We herein report accurate bond dissociation energies (BDEs) for a set of 18 molecules using the high-level W2 thermochemical protocol. The BDEs (at 298 K) of the species in this set range from 162.2 kJ mol-1 (N-bromopyrrole) to 260.6 kJ mol-1 ((CHO)2NBr). In order to compute BDEs of larger systems, for which W2 theory is not applicable, we have benchmarked a wide range of more economical theoretical procedures. Of these, G3-B3 offers the best performance (root-mean-square deviations = 2.9 kJ mol-1), and using this method, we have computed NBr BDEs for four widely used N-brominated compounds. These include (BDEs are given in parentheses): N-bromosuccinimide (281.6), N-bromoglutarimide (263.2), N-bromophthalimide (274.7), and 1,3-dibromo-5,5-dimethylhydantoin (218.2 and 264.8 kJ mol-1).
- W2 theory
- density functional theory
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics
- Physical and Theoretical Chemistry