Question

Arrange in the order of nucleophilicity $H{O^ - },C{H_3}{O^ - },C{H_3} \equiv {C^ - },C{H_3}CO{O^ - }$
$
  A)O{H^ - } > C{H_3}{O^ - } > C{H_3} \equiv {C^ - } > C{H_3}CO{O^ - } \\
  B)C{H_3}CO{O^ - } > O{H^ - } > C{H_3}{O^ - } > C{H_3} \equiv {C^ - } \\
  C)O{H^ - } < C{H_3}{O^ - } < C{H_3} \equiv {C^ - } < C{H_3}CO{O^ - } \\
  D)C{H_3}CO{O^ - } < O{H^ - } < C{H_3}{O^ - } > C{H_3} \equiv {C^ - } \\
 $

Answer 1

Hint: We know that the term nucleophile means nucleus loving. We can define a nucleophile as having the ability of an electron rich species to be attracted to the nuclear charge that is positive of an electron deficient species, which is an electrophile. We can call the ability of the nucleophile to attract the positive nuclear charge of electrophile as nucleophilicity. The system would be nucleophilic, if there were more electrons present.

Complete step by step answer:
Basicity and nucleophilicity have similar properties. Nucleophiles are generally bases. Example: $H{O^ - },R{O^ - }$.
Species that carry neutral charge (or) negative charge are nucleophiles. As the nuclear charge increases, the nucleophilicity also increases.
While moving across a row, the trend of nucleophilicity is similar to that of basicity.
We know that from right to left across a row, the basicity increases, similarly nucleophilicity increases.
As the atomic size increases, nucleophilicity also increases.
We know the nucleophile means nucleus loving, and a species that has the ability to attract to the positive charge of the electrophile is called a nucleophile and the process is called nucleophilicity.
In given set of ions, that is $H{O^ - },C{H_3}{O^ - },C{H_3} \equiv {C^ - },C{H_3}CO{O^ - }$
We have to know that hydroxide ion would be stronger nucleophiles than acetate ion since in the acetate ion, the negative charge takes place in resonance with the carboxylic group.
Due to the positive inductive effect, methoxide ion is more nucleophilic than hydroxide ion.
The ion of Acetylides is stronger nucleophile than methoxide ion due to the presence of negative charge on carbon atoms that is less electronegative.
In polar aprotic solvent, we can give the increasing order of nucleophilicity as,
$C{H_3}CO{O^ - } < O{H^ - } < C{H_3}{O^ - } > C{H_3} \equiv {C^ - }$
$\therefore $Option (D) is correct.

Note:
We have to remember that in protic solvent, basicity decreases and nucleophilicity increases and when basicity increases, there is decrease in nucleophilicity while moving down a group. Some of neutral nucleophiles are water, ammonia, primary amine, carboxylic acids etc. Some of the charged nucleophiles are bromide ion, iodide ion, cyanide ion, hydroxide ion, chloride ion etc. Some of the factors that nucleophilicity depends on are charge, solvent, nature of substituents, basicity and polarizability.