Q29 / 180 · AIIMS 2017 · Chemistry

What is the correct order of basicity among the following compounds? Figure

  • A
    $\mathrm{II}>\mathrm{I}>\mathrm{III}>\mathrm{IV}$
  • B
    $\mathrm{I}>\mathrm{II}>\mathrm{III}>\mathrm{IV}$
  • C
    III $>$ I $>$ II $>$ IV
  • Correct answer
    D
    I $>$ III $>$ II $>$ IV

Solution

Figure
Figure
The conjugate acid formed by addition of a proton to I is stabilised by two equivalent resonance structures and hence, compound I is the most basic. Further $2^{\circ}$ amines (III) are more basic than $1^{\circ}$ amines (II) while amides (IV) are least basic due to delocalisation of lone pair of electrons of $\mathrm{N}$ over the $\mathrm{CO}$ group. Thus, the order is : I $>$ III $>$ II $>$ IV.

Hence, the correct answer is option: 'D'.

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