Question

Define nucliophilic substitution reacvtiopn

Answer 1

It is the reaction in which electron rich species attack on electron deficient species.
nucleophils have partially negative charge on it..

Answer 2

In organic chemistry and inorganic chemistry, nucleophilic substitution is a fundamental class of reactions in which a leaving group is replaced by an electron rich compound (nucleophile). The whole molecular entity of which the electrophile and the leaving group are part is usually called the substrate.[1][2] The nucleophile essentially attempts to replace the leaving group as the primary substituent in the reaction itself, as a part of another molecule.

The most general form of the reaction may be given as the following:

Nuc: + R-LG → R-Nuc + LG:

The electron pair (:) from the nucleophile (Nuc) attacks the substrate (R-LG) forming a new bond, while the leaving group (LG) departs with an electron pair. The principal product in this case is R-Nuc. The nucleophile may be electrically neutral or negatively charged, whereas the substrate is typically neutral or positively charged.

An example of nucleophilic substitution is the hydrolysis of an alkyl bromide, R-Br, under basic conditions, where the attacking nucleophile is the OH− and the leaving group is Br−.

R-Br + OH− → R-OH + Br−

Nucleophilic substitution reactions are commonplace in organic chemistry, and they can be broadly categorized as taking place at a saturated aliphatic carbon or at (less often) an aromatic or other unsaturated carbon center.