Mechanism of redox reactions of oxopiperidinium salts and piperidinoxyl radicals with iodides and iodine

Conclusions

• 1. At pH ⪞3 oxopiperidinium salts

  

  are reversibly reduced by iodides to piperidinoxyl radicals

  

  . The intermediate particles of this reaction are apparently ion pairs$\left( {\mathop N\limits^ + = O, I^ - } \right)$ and the anion-radical İ ⁻₂ .

• 2. At pH ⪝1 oxopiperidinium salts

  

  and radicals

  

  are reduced by iodides to hydroxypiperidinium salts

  

  . Reduction of

  

  and

  

  to

  

  under these conditions is due to disproportionation of

  

  and its protonated form to

  

  and

  

  , to protonation of

  

  , and to conversion of

  

  under the influence of I⁻ to

  

  .