Question

Select the correct order of basic nature:
A. $C{H_3}C{H^ - }_2 > C{H_2} = C{H^ - } > CH \equiv {C^ - } > O{H^ - }$
B. $C{H_3}C{H^ - }_2 > CH \equiv {C^ - } > C{H_2} = C{H^ - } > O{H^ - }$
C. $C{H_3}C{H^ - }_2 > O{H^ - } > CH \equiv {C^ - } > C{H_2} = C{H^ - }$
D. $O{H^ - } > CH \equiv {C^ - } > C{H_2} = C{H^ - } > C{H_3}C{H^ - }_2$

Answer 1

Hint: We can approach this problem by finding out the acidic nature of the compounds and then we will get order of the basic nature of the ions. We know that the conjugate base is obtained by removing a proton from a compound.

Complete step by step solution:
> The given ions are $C{H_3}C{H^ - }_2,C{H_2} = C{H^ - },CH \equiv {C^ - }$ and $O{H^ - }$. On addition of a proton $\left( {{H^ + }} \right)$ to the given ions we have found that these compounds are $C{H_3}C{H_3},C{H_2} = C{H_2},CH \equiv CH$ and ${H_2}O$. So we can find the order of acidic nature of the compounds. We know that a hydrogen tends to be acidic when it is attached to an electronegative atom or we can say that the conjugate base will be more stable on the localization of the negative charge on a more electronegative atom. The acidic nature of alkanes , alkenes and alkyne depends on the percentage s character. Alkanes used to be $s{p^3}$ hybridized so they have $25\% $ s-character similarly alkene possess $33.3\% $ s- character and alkynes possess $50\% $ s- characters. So their order of acidity is Alkynes > alkenes> Alkanes. Water will have less acidic nature than alkane, alkene and alkyne. Hence the order of acidic strength of the given compounds are ${H_2}O > CH \equiv CH > C{H_2} = C{H_2} > C{H_3}C{H_3}$. We have studied that the conjugate base of a strong acid will be weak so the order of the given conjugate bases of the compounds will be $C{H_3}C{H^ - }_2 > C{H_2} = C{H^ - } > CH \equiv {C^ - } > O{H^ - }$. Hence option A is the correct order of basic nature.

Note: We know that the conjugate base of a stronger acid used to be a weak base and vice versa so here we have found the order of acidic nature of the given compounds and that order gives us the order of basic nature of compounds.