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Rate of solvolysis of t-halide Me(3)CBr ...

Rate of solvolysis of t-halide `Me_(3)CBr` is found to be `3xx10^(-4)` times faster in 50% aq ethanol than in ethanol alone.

Text Solution

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Hydrolysis of `(CH_(3))_(3)CBr` to `(CH_(3))_(3)C-OH` follows `S_(N)1` pathway. For a halide that undergoes hydrolysis by the `S_(N)1` mode, reaction rate increases with increase in the polarity of the solvent (i.e. increase in dielectric constane a and its ion-solvating ability). Water is a better ionizing solvent than ethanol.
So the rate of hydrolysis of `(CH_(3))_(3)C-Br` increases largely when pure ethanol is replaced by 80% aqueous ethanol since more polar water molecules bring extra stability to the T.S. of the carbonium ion formation step, i.e. the rate determining step.
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