Question
What is nucleophilic substitution reaction ? Write down different products obtained from alkyl halides.
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Answer
→ Nucleophiles are electron rich species. Therefore, they attack at that part of the substrate molecule which is electron deficient.
→ The reaction in which a nucleophile replaces already existing nucleophile in a molecule is called nucleophilic substitution reaction.
→ Haloalkanes are substrate in these reactions.
→ In this type of reaction, a nucleophile reacts with haloalkane (the substrate) having a partial positive charge on the carbon atom bonded to halogen.
→ A substitution reaction takes place and halogen atom, called leaving group departs as halide ion. Since the substitution reaction is initiated by a nucleophile, it is called nucleophilic substitution reaction.
→ It is one of the most useful classes of organic reactions of alkyl halides in which halogen is bonded to SP³ hybridised carbon.
$R - X + Nu ^{-} \rightarrow R - Nu + X ^{-}$
→ The reaction in which a nucleophile replaces already existing nucleophile in a molecule is called nucleophilic substitution reaction.
→ Haloalkanes are substrate in these reactions.
→ In this type of reaction, a nucleophile reacts with haloalkane (the substrate) having a partial positive charge on the carbon atom bonded to halogen.
→ A substitution reaction takes place and halogen atom, called leaving group departs as halide ion. Since the substitution reaction is initiated by a nucleophile, it is called nucleophilic substitution reaction.
→ It is one of the most useful classes of organic reactions of alkyl halides in which halogen is bonded to SP³ hybridised carbon.
$R - X + Nu ^{-} \rightarrow R - Nu + X ^{-}$
| Reagent | Nucleophile (Nu-) | Substitution product R-Nu | Class of main product |
| NaOH (KOH) | HO- | ROH | Alcohol |
| H₂O | H₂O | ROH | Alcohol |
| NaOR' | R'O- | ROR' | Ether |
| Nal | Γ | R-I | Alkyl iodide |
| NH3 | NH3 | RNH2 | Primary amine |
| R'NH₂ | R'NH2 | RNHR' | Sec. amine |
| R'R"NH | R'R"NH | RNR'R" | Tert. amine |
| KCN | $\overline{ C } \equiv N :$ | RCN | Nitrile (cyanide) |
| AgCN | Ag-CN | RNC | Isonitrile (isocyanide) |
| KNO2 | $O = N - O$ | R-O-N=O | Alkyl nitrite |
| AgNO2 | $Ag -\ddot{ O }- N = O$ | R-NO2 | Nitroalkane |
| R'COOAg | R'COO- | R'COOR | Ester |
| LiAlH 4 | H | RH | Hydrocarbon |
| R'-M+ | R' | RR' | Alkane |
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