Question

How do you identify an electrophile from a nucleophile?

Answer 1

Hint Nucleophile and electrophile are the intermediate of a reaction which mainly acts as an attacking reagent. Electrophile and nucleophiles are formed by heterolytic bond dissociation. Carbocation and Carbanion are the most common electrophile and nucleophile formed by the heterolytic bond dissociation of organic compounds respectively. Carbene nitrene and free radical are the most common electrophile formed as a reaction intermediate.

Complete answer–
An electrophile shows affinity toward electrons while a nucleophile shows affinity toward nucleus.
Electrophile is those species which carry positive charge and vacant orbitals or are electron deficient. These species attack regions of high electron density in a molecule and show high affinity for electrons. There are mainly two types of electrophiles –
(i) Positively charged electrophiles – that electrophile which have electron deficiency and carry a positive charge in the central atom. For e.g. ${{\text{H}}^{\text{+}}}\text{,}\,\text{CH}_{\text{3}}^{\text{+}}\text{,}\,\text{NO}_{\text{2}}^{\text{+}}\text{,}\,\text{and}\,\text{R-}{{\text{C}}^{+}}\text{=O}$
(ii) Natural electrophiles- that electrophile which does not carry positive charge but are electron deficient species. These species have vacant orbital or incomplete octets. For e.g. $\text{B}{{\text{F}}_{\text{3}}}\text{,}\,\text{S}{{\text{O}}_{\text{3}}}\text{,}\,\text{RCOCl,}\,\text{and}\,\text{AlC}{{\text{l}}_{\text{3}}}$.
Nucleophile is those species which carry a negative cleavage or electron rich species or which electron is called nucleophile. They attack a low electron density region and have affinity toward the nucleus. Electrophiles are also two types –
(i) Negatively charged nucleophile - $\text{B}{{\text{r}}^{\text{-}}}\text{,}\,\text{C}{{\text{H}}^{\text{-}}}\text{,}\,\text{and}\,\text{CH}_{\text{3}}^{\text{-}}$
(ii) Neutral nucleophiles - $\text{N}{{\text{H}}_{\text{3}}}\text{,ROH,}\,\text{and}\,\text{RN}{{\text{H}}_{\text{2}}}$

Note – Electron withdrawing group decreases the stability of electrophile and electron releasing group increases the stability of electrophiles. Electron withdrawing groups increase the stability of nucleophiles while electron releasing groups destabilise the nucleophiles.