Deamination of 2-Methyl-2-propanamine Induced by Hydroxyl Radicals and Metal Ions: A Comparison between the Rates of β Elimination of Ammonia and Water

The reactions of CH₂C(CH₃)₂NH₃with Cu⁺(aq) and Cr(H₂O)₆²⁺were studied using the pulse radiolysis technique. The formation of the unstable [Cu^II-CH₂C(CH₃)₂(NH₃⁺)]⁺and [(H₂O)_sCr^III-CH₂C(CH₃)₂(NH₃⁺)]²⁺ions was observed in these reactions. These complexes decompose via /S elimination of NH₃to yield 2-methylpropene, ammonia, and Cu²⁺(aq) or Cr³⁺(aq). The rates of these β-elimination reactions are considerably slower than those of the analogous β-hydroxyl elimination. It is suggested that the rates of the β-elimination processes are correlated to the strengths of the C-O and C-N bonds, which are cleaved in these reactions. A valence-bond analysis coupled with some ab-initio SCF-MO computations explains the effect of protonation on these bond strengths.