Depto. Química Orgánica

STERIC EFFECTS

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15/07/2017
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The SN2 reaction is very sensitive to steric hindrance because, in the TS, the reacting carbon is a trigonal bipyramid where there are five groups in close proximity.
The volume of the R groups critically determines the energy of the TS and hence the reaction rate.
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The increase in the number of substituents at the reacting carbon induces a drastic diminution of the reaction rate.
The linear elongation of the chain of one of the substituents slightly decreases the reaction rate.
 In clear contrast, the branching elongation of the chain severely decreases the reaction rate.