Lithation of 2-chloropyridine with LDA

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I found that the proton at the C-3 position is removed to allow for a nucleophillic attack at the C-3 position

Removing of C-3 H⁺ will disable nucleophilic substition at this place (Nu^- will not attach to C^-).

LiN[CH(CH₃)₂]₂ is strong base so substition follows rather elimination-addition mechanism (product will be mixture of 2- and 3-substituted pyridine).