Q.Differentiate Nucleophile and Electrophile.

A nucleophile is electron-rich and donates an electron pair to a bond; an electrophile is electron-deficient and accepts an electron pair — they are complementary reactive species.

Nucleophile ("nucleus-loving"): a chemical species that is electron-rich, possessing either a lone pair of electrons or a full negative charge (or a region of high electron density, such as a pi bond), which it can DONATE to form a new covalent bond. Because it seeks out a positively charged or electron-deficient centre, nucleophiles attack electrophilic (electron-poor) sites. Examples: OH-, CN-, Cl-, NH3, H2O, alkenes (C=C pi bonds can also act as nucleophiles). Nucleophiles are Lewis bases.

Electrophile ("electron-loving"): a chemical species that is electron-deficient, either bearing a positive charge or having an incomplete octet / empty orbital, which makes it seek out and ACCEPT an electron pair from elsewhere to form a new bond. Electrophiles attack nucleophilic (electron-rich) sites. Examples: H+, carbocations (R3C+), NO2+ (nitronium ion), BF3, AlCl3 (Lewis acids with an incomplete octet on the central atom). Electrophiles are Lewis acids.

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Nucleophiles and electrophiles are opposite in their electronic behaviour: a nucleophile is electron-rich and donates an electron pair to form a new bond, while an electrophile is electron-deficient and accepts an electron pair.

Three key differences:

1. Nature/electron count: A nucleophile ('nucleus-loving') is a species that is rich in electrons — it may be neutral with a lone pair, or negatively charged. An electrophile ('electron-loving') is a species that is deficient in electrons — it may be neutral with an incomplete octet, or positively charged.

2. Role in bond formation: A nucleophile DONATES an electron pair to form a new covalent bond with an electron-deficient centre. An electrophile ACCEPTS an electron pair from an electron-rich centre to form the new bond.

3. Examples: Common nucleophiles include OH-, CN-, NH3, H2O, alkoxide ions (RO-), and halide ions (Cl-, Br-) — species with a lone pair or negative charge to donate. Common electrophiles include H+, NO2+ (nitronium ion), carbocations (R+), and Lewis acids such as AlCl3 or BF3 — species that are positively charged or have an incomplete octet. …