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       #Post#: 1074--------------------------------------------------
       Mechanisms
   DIR By: Chris
       Date: November 9, 2012, 4:46 am
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       Why does hydrolysis of bromomethane proceed by SN2 mechanism
       while that of 2-bromo-2-methylpropane proceed by SN2 mechanism
       #Post#: 1085--------------------------------------------------
       Re: Mechanisms
   DIR By: Michel
       Date: November 9, 2012, 12:53 pm
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       --- Quote from: Chris link ---
       >
       > Why does hydrolysis of bromomethane proceed by SN2 mechanism
       while that of 2-bromo-2-methylpropane proceed by SN2 mechanism
       >
       --- End Quote ---
       
       I assume you made a typo, probably ought to read :"while that of
       2-bromo-2-methylpropane proceeds by SN2 mechanism.
       The simplest answer is that the first step of hydrolysis of
       bromomethane involves the OH- 'approaching the bromomethane
       molecule from the side opposite the Br leaving group, resulting
       in a transition complex, followed by a walden inversion and
       finally substitution of OH-. Why is this so? because the CH3Br
       cannot form a carbocation, a 1°  carbocation is highly unstable.
       in the case of 2-bromo-2-methylpropane, the first step of the
       reaction involves the formation of a stabler 3° carbocation
       followed by nucleophilic attack on the carbocation by the OH-
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