Which of the following is least basic .

Options

A. `CH_(3)CH_(2)CH_(2)NH_(2)`
B. `HC-=C CH_(2)NH_(2)`
C. `H_(2)C=CHCH_(2)NH_(2)`
D. `CH_(3)CH_(2)CH_(2)NHCH_(3)`

Answer

B

Explanation

Compound (4) a secondary amine is the most basic To decide among the rest we take into consideration the hybridization of the Beta -carbon atom The more s-character it has the more electron with drawing(by induction ) and base weakeing it will be Thus the decreasing order of basicity is
`CH_(3)underset(sp^(3))underset(uarr)CH_(2)CH_(2)NH_(2)gtH_(2)C=underset(sp^(2))underset(uarr)(CHCH_(2)NH_(2)gtCH)=underset(sp)underset(uarr)(C CH_(2))NH_(2) ` .