question_answer

Compare the basicities of the following amines and justify the order : \[\underset{\begin{smallmatrix}   \\  \text{(I)} \end{smallmatrix}}{\mathop{C{{H}_{2}}=CHC{{H}_{2}}N{{H}_{2}}}}\,\]        \[\underset{(II)}{\mathop{C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}N{{H}_{2}}}}\,\]        \[\underset{(III)}{\mathop{CH\equiv CC{{H}_{2}}N{{H}_{2}}}}\,\]

Answer:

                 The relative basic strengths are :                 \[\underset{\begin{matrix}    (I)  \\    {}  \\ \end{matrix}}{\mathop{\underset{\begin{smallmatrix}   \\  (III) \end{smallmatrix}}{\mathop{CH\equiv CC{{H}_{2}}N{{H}_{2}}}}\,\,\,\,\,\,\,\,<\,\,\,C{{H}_{2}}=CHC{{H}_{2}}N{{H}_{2}}\,\,\,\,\,\,\,<\,\,\,\underset{\begin{smallmatrix}   \\  (II) \end{smallmatrix}}{\mathop{C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}N{{H}_{2}}}}\,}}\,\,\] The electron withdrawing nature of the different groups is : \[\underset{\begin{smallmatrix}   \\  \text{(propargyl-sp}\,\text{hybridised)} \end{smallmatrix}}{\mathop{CH\equiv CCH_{2}^{-}}}\,>\underset{\begin{smallmatrix}   \\  \text{(allyl-s}{{\text{p}}^{\text{2}}}\,\text{hybridised)} \end{smallmatrix}}{\mathop{C{{H}_{2}}=CHCH_{2}^{-}}}\,\,\,\,>\underset{\begin{smallmatrix}   \\  \text{(n-propyl-s}{{\text{p}}^{\text{3}}}\,\text{hybridised)} \end{smallmatrix}}{\mathop{C{{H}_{3}}C{{H}_{2}}CH_{2}^{-}}}\,\] In the light of this, the relative order of basic strengths is justified.