Arrange the indicated hydrogens in decreasing order of their acidic strength.

Step-by-step solution

The acidic strength of the given hydrogens can be determined by comparing the stability of their respective conjugate bases or their typical pK_a values. Hydrogen (iii) is attached to a positively charged nitrogen atom in an iminium ion ( >C=N^+(H)- ). Deprotonation neutralizes the positive charge, resulting in a stable, neutral imine. This makes it the most acidic proton among the three, with a typical pK_a in the range of 5-10 . Hydrogen (ii) is attached to an sp -hybridized carbon atom of a terminal alkyne ( -C