Q. 5 P - Organic Chemistry (Mcmurry)

Question

An electrostatic potential map of boron trifluoride is shown. Is ${\mathbf{\text{BF}}}_{\mathbf{\text{3}}}$ likely to be a nucleophile or an electrophile? Draw a Lewis structure for ${\mathbf{\text{BF}}}_{\mathbf{\text{3}}}$ , and explain your answer.

Step-by-Step Solution

Answer

${\text{BF}}_{\text{3}}$ acts as an electrophile.

Step 1: Electrophiles and nucleophiles

Electrophiles are positively charged species that attack the electron-rich center.

For example, ${\text{BF}}_{\text{3}}$,  ${\text{H}}_{\text{3}}{\text{O}}^{\text{ + }}$, and ${\text{AlCl}}_{\text{3}}$ 

Nucleophiles are the electron-rich centers or negatively charged species that attack electron-deficient centers.

Neutral molecules containing lone pair of an electron can also act as a nucleophile. For example, ${\text{Cl}}^{\text{ - }}$, ${\text{I}}^{\text{ - }}$, ${\text{NH}}_{\text{3}}$, etc.

Step 2: BF 3 as an electrophile

In ${\mathrm{BF}}_3$ , boron has three electron couples with three electrons of fluorine. So in ${\mathrm{BF}}_3$ , boron has six electrons in its outer shell which indicates that the octet is not complete. Since ${\mathrm{BF}}_3$ has a vacant p-orbital,  ${\mathrm{BF}}_3$ can accept electrons in its vacant p-orbital. Therefore ${\mathrm{BF}}_3$ act as an electrophile.