MCQ Detailed View

In organic chemistry, species are classified as electrophiles or nucleophiles based on how they participate in reactions. Electrophiles are electron-deficient species that seek electrons, while nucleophiles are electron-rich species that donate electrons. Correctly identifying electrophiles is essential to predict reaction mechanisms.

Among the given options:

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  NH₃ (ammonia) has a lone pair of electrons on the nitrogen atom. This makes it electron-rich and capable of donating electrons to electron-deficient centers. Therefore, NH₃ acts as a nucleophile, not an electrophile.

  
  


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  Br⁺ (bromonium ion) is positively charged and electron-deficient, making it a strong electrophile.

  
  


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  H⁺ (proton) is the simplest electrophile because it has no electrons and readily accepts electron density from a nucleophile.

  
  


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  BF₃ (boron trifluoride) is electron-deficient since boron has only six valence electrons in this compound. It strongly accepts electron pairs, classifying it as a Lewis acid and electrophile.

  
  

The key point here is that electrophiles are usually either positively charged ions (like H⁺, Br⁺, NO₂⁺) or neutral molecules with electron deficiency (like BF₃, AlCl₃, SO₃). Nucleophiles, on the other hand, are negatively charged ions or neutral molecules with lone pairs (such as OH⁻, CN⁻, NH₃, and H₂O).

Therefore, the correct answer is NH₃, as it donates electrons instead of accepting them. Recognizing the difference between electrophiles and nucleophiles helps in understanding reaction types like SN1, SN2, E1, E2, and electrophilic substitution in aromatic compounds.