Question

Which one is not an electrophile?

• A. ${\mathrm{BF}}_3$
• B. ${\mathrm{NH}}_3$
• C. ${\mathrm{SO}}_3$
• D. ${\mathrm{AlCl}}_3$

Answer 1

The correct option is B

${\mathrm{NH}}_3$

Explanation for the correct option:

Option (b):

• An electrophile is a reagent that is used in taking the electron pair from the reactive site.
• It is an electron-deficient.
• The electrophile attacks the substrate's electron-rich centre (nucleophilic centre).
• Ammonia is a nucleophile because it has two lone pairs on nitrogen that can be donated easily during the course of the reaction. It is a strong base.
• 

Explanation for the incorrect option:

Option (a):

• Boron trifluoride has an empty p orbital and so it is electron deficient. So, it is an electrophile.
• 

Option (c):

• ${\mathrm{SO}}_3$ is a highly polar molecule with a positive charge on the sulphur atom. It attracts the ring electrons.
• There is three electronegative oxygen attached to the sulphur atom. So, it is an electrophile.
• 

Option (d):

• Aluminium chloride also has an empty p orbital and it is electron deficient. So, it is electrophilic in nature.
• 

Final answer:

Hence, option (b) is the correct answer.