A Guidebook to Mechanism in Organic Chemistry

Effect of Structure

ions: thus the rate of hydrolysis (Sjyl) of t-butyl chloride is 30,000
times as fast in 50 per cent aqueous ethanol as in ethanol alone. The
effect of change of solvent on a halide wh,ose hydrolysis proceeds by
the Sjy2 mechanism throughout is much less marked and the direction
of the effect on rate of reaction is not always readily predictable. This
difference in the effect of change of solvent on reaction rate in the two
cases may be of help in determining whether a particular displacement
reaction is proceeding by the SN\ or Sjv2 mechanisms.

a EFFECpOF STRUCTURE
An interesting contrast is provided by hydrolysis of the series of
halides:
Me Me
CH 3 —Br Me—CHS—Br ^H—Br Me-^C—Br
/ /
Me Me
The first and last members are described in the literature as under­
going ready hydrolysis, the two intermediate members being more
resistant. Measurement of rates of hydrolysis with dilute alkali in
aqueous ethanol gives the plot*

i-Pr t-Bu

Based on Ingold, Structure and Mechanism

in Organic Chemistry, by permission of

Cornell University Press.