Question
What is the decreasing order of strength of the bases $$O{H^ - },NH_2^ - ,HC \equiv {C^ - }$$ and $$C{H_3}CH_2^ - ?$$
A.
$$C{H_3}CH_2^ - > NH_2^ - > HC \equiv {C^ - } > O{H^ - }$$
B.
$$HC \equiv {C^ - } > C{H_3}CH_2^ - > NH_2^ - > O{H^ - }$$
C.
$$O{H^ - } > NH_2^ - > HC \equiv {C^ - } > C{H_3}CH_2^ - $$
D.
$$NH_2^ - > HC \equiv {C^ - } > O{H^ - } > C{H_3}CH_2^ - $$
Answer :
$$C{H_3}CH_2^ - > NH_2^ - > HC \equiv {C^ - } > O{H^ - }$$
Solution :
Stronger the acid, weaker the conjugate base. Since acid character follows the order
$${H_2}O > HC \equiv CH > N{H_3} > C{H_3} - C{H_3}$$
( Acid character ),
the basic character of their conjugate bases decreases in the reverse order, i.e.,
$$C{H_3}CH_2^ - > NH_2^ - > HC \equiv {C^ - } > O{H^ - }$$
(Basic character)