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JEE Main levelOne or more correct optionsDifficulty 2 of 3g2087

Which of the following statements about guanidine, , are correct?

  1. AIt is protonated at the imine nitrogen
  2. BThe guanidinium ion has three equivalent C-N bonds due to resonance
  3. CIt is a stronger base than methylamine (pKaH of guanidinium 13.6, of methylammonium 10.6)
  4. DIt is a weaker base than aniline

Answer: A, B, C

Protonation of the =NH nitrogen gives a symmetrical resonance-stabilised guanidinium ion with three equivalent C-N bonds, hence pKaH 13.6, greater than methylammonium (10.6) and anilinium (4.6). D is therefore false.
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