Question

write the Salient features of SN2 mechanism​

Answer 1

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i. Single step mechanism with simultaneous bond breaking and bond forming.

ii. Backside attack of nucleophile : The nucleophile attacks the carbon undergoing substitution from the side opposite to that of the leaving group. This is to avoid steric repulsion (repulsion due to bulkyness of the groups) and electrostatic repulsion between the incoming nucleophile and the leaving group.

iii. In the transition state (T.S.) the nucleophile and leaving groups are bonded to the carbon with partial bonds and carry partial negative charge. (Thus, the total negative charge is diffused.)

iv. The T.S. contains pentacoordinate carbon having three σ (sigma) bonds in one plane making bond angles of 1200with each other and two partial covalent bonds along a line perpendicular to this plane.

v. When SN2 reaction is brought about at chiral carbon (in an optically active substrate), the product is found to have opposite configuration compared to that of the substrate. In other words, SN2 reaction is found to proceed with inversion of configuration. This is like flipping of an umbrella It is known as Walden inversion. The inversion in configuration is the result of backside attack of the nucleophile.

Answer 2

Explanation:

The SN2 reaction mechanism involves the nucleophilic substitution reaction of the leaving group (which generally consists of halide groups or other electron-withdrawing groups) with a nucleophile in a given organic compound.

The rate-determining step of this reaction depends on the interaction between the two species, namely the nucleophile and the organic compound.

SN2 reaction mechanism requires the attack of nucleophile from the back side of the carbon atom. So the product assumes a stereochemical position opposite to the leaving group originally occupied. This is called inversion of configuration. The SN2 reaction is a good example of stereospecific reaction,