Phenylethane can be chlorinated in two different positions in
the alkane side chain and the alkaline hydrolysis of the products has been
studied in aqueous ethanol solvent. A solution 0.1M with respect to both
1-chloro-2-phenylethane and sodium hydroxide is allowed to react at 30oC.
Portions of the mixture are withdrawn at definite times and titrated with a
standard acid solution.
| time/days | 0.01 | 2.0 | 4.0 | 6.0 | 8.0 | 10.0 |
| titre/cm3 | 23.2 | 18.3 | 15.1 | 12.7 | 11.0 | 9.7 |
The experiment was repeated using 1-chloro-1-phenylethane with the following results:
| time/days | 0.01 | 2.0 | 4.0 | 6.0 | 8.0 | 10.0 |
| titre/cm3 | 21.2 | 18.7 | 16.3 | 14.2 | 12.6 | 11.0 |
By plotting appropriate graphs determine whether the reactions are first order or second order. On the basis of your conclusions, propose tentative mechanisms for both reactions.
Hint
plot volume against time
measure the gradient (to calculate rate) at each concentration (assume volume
proportional to concentration)
Plot rate against concentration
Plot rate against concentration squared
Propose SN1 or SN2
mechanisms