Question

The nucleophilicities of $R{O}^{-}$, $H{O}^{-}$, $RCO{O}^{-}$, ROH and $H_{2}O$ are of the order :

• A. $H{O}^{-}>R{O}^{-}>H_{2}O>ROH>RCO{O}^{-}$
• B. $R{O}^{-}>H{O}^{-}>RCO{O}^{-}>ROH>H_{2}O$
• C. $H_{2}O>ROH>RCO{O}^{-}>H{O}^{-}>R{O}^{-}$
• D. $ROH>H_{2}O>H{O}^{-}>RCO{O}^{-}>R{O}^{-}$

Answer 1

The correct option is B $R{O}^{-}>H{O}^{-}>RCO{O}^{-}>ROH>H_{2}O$

Since a nucleophile is a species that is donating a pair of electrons, it’s reasonable to expect that its ability to donate electrons will increase as it becomes more electron-rich, the conjugate base is always a better nucleophile.

$R{O}^{-}$ is strong nucleophile than $O{H}^{-}$ due to the presence of the inductive effect of $R$ group electron density increases.

In $RCO{O}^{-}$ the electrons are in conjugation, therefore, are not freely available to attack as a nucleophile.

The neutral species $ROH$ and $H_{2}O$ are weak nucleophiles. $ROH$ due to the inductive effect of alkyl better nucleophile than $HOH$.

The order of nucleophile strength is $R{O}^{-}>O{H}^{-}>RCO{O}^{-}>ROH>HOH$

Hence, the correct option is $B$