Question

Mention four factors that affect nucleophilicity.

Answer 1

Four factors that effect nucleophilicity are:
1. Charge - The conjugate base is always a stronger nucleophile
$H{O}^{\ominus }$ > $H_{2}O$ $H_2{N}^{\ominus }$ > $N{H}_3$ > $H{S}^{\ominus }$ > $H_{2}S$
2. Electronegativity - Nucleophilicity decreases with EN (across a row)
$H_3{C}^{\ominus }$ > $H_{2}N\ominus$ > $H{O}^{\ominus }$ > $F^{\ominus }$
$H_{3}N:>H_2\ddot{O}:>H\underset{..}{\ddot{F:}}$
3. Solvent - Hydrogen bonding solvents invert nucleophilicity
$I^{\ominus }$ > $B{r}^{\ominus }$ > $C{l}^{\ominus }$ > $F^{\ominus }$
(polar protic solvents)
$F^{\ominus }$ > $C{l}^{\ominus }$ > $B{r}^{\ominus }$ > $I^{\ominus }$
(polar aprotic solvents)
4. Steric bulk - Nucleophilicity decreases with increasing steric bulk