Nucleophilic substitution reactionThe reaction in which a nucleophile replaces already existing nucleophile in a molecule is called nucleophilic substitution reaction.
* Nucleophiles are electron rich species so they attack at that part of substrate molecule which is electron deficient.
Ambident Nucleophiles
Nucleophiles which can attack through two different sites are called ambient nucleophiles.
Eg- Cyanide ion exists as hybrid of following two structures.
It can attack either through carbon to form cyanides or through nitrogen to form isocyanides.
Q Haloalkanes react with KCN to form alkyl cyanide as major or main product while AgCN forms isocyanide as the chief product. explain.
Ans-
KCN is ionic and provide cyanide ion in solutions. Both carbon and nitrogen atoms are in a position to donate electron pairs. The attack takes place mainly through carbon atom and not through nitrogen atoms since C-C bond is more stable than C-N bond. AgCN is mainly covalent in nature and nitrogen is free to donate electron pairs forming isocyanide as the chief product.
Q Haloalkanes react with KNO2 to form alkyl nitride as major or main product while AgNO2 forms alkylnitrito as the chief product. explain.
Ans-
KNO2 is ionic and provide nitrate ion in solutions. Both nitrogen and oxygen atoms are in a position to donate electron pairs. Since nitrogen is less electronegative than oxygen, the lone pair of electrons on nitrogen are more easily available for bond formation. Also, AgNO2 IS mainly covalent in nature. So, AgNO2 gives alkylnitrito as the chief product.
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