Q. The correct order of increasing basicity of the given conjugate bases (R=$CH_{3}$) is

A) $RCO\overline{O} < HC \equiv \overline{C} < \overline{R} < \overline{N}H_{2}$
B) $\overline{R} < HC \equiv \overline{C} < RCO\overline{O} < \overline{N}H_{2}$
C) $RCO\overline{O} < NH_{2} < HC \equiv \overline{C} < \overline{R}$
D) $RCO\overline{O} < HC \equiv \overline{C} < \overline{N}H_{2} < \overline{R}$
Explanation

(d)
[image:12_image335.emf]:In carboxylate ion, the negative charge is present on oxygen, a most electronegative element here, thus it is resonance stabilised.
$HC \equiv C^{-}$: Carbon is $sp$-hybridised so its electronegativity is increased higher relative to nitrogen.
$\overline{N}H_{2}:$ Nitrogen is more electronegative than $sp^{3}$-hybridised C-atom. From the above discussion, it is clear that the order of the stability of conjugated bases is as
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ RCOO^{-} > HC \equiv C^{-} > \overline{N}H_{2} > R^{-}$
and higher is the stability of conjugated bases, lower will be basic character. Hence, the order of basic character is as
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ RCOO^{-} < HC \equiv C^{-} < \overline{N}H_{2} < R^{-}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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