Edexcel IAL Chemistry 11.9 SN1 and SN2 rate evidence

Determine which concentrations appear in the rate law, connect first-order RX dependence to carbocation formation and two-reactant dependence to concerted attack.

Exam points

Link rate = k[RX] to an SN1 slow ionisation step and carbocation intermediate.
Support SN2 when rate is first order in both halogenoalkane and nucleophile.
Interpret a two-peak SN1 profile with a carbocation intermediate between transition states.

[Maximum number: 1]

The equation shows the hydrolysis of a bromoalkane.

\mathrm{RBr}+\mathrm{OH}^{-} \rightarrow \mathrm{ROH}+\mathrm{Br}^{-}

The rate equation is rate $=k[\mathrm{RBr}]$
RBr is most likely to be

bromomethane

2-bromopropane

1-bromo-2-methylpropane

2-bromo-2-methylpropane

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11.9—Knowledge of the rate equations for the hydrolysis of halogenoalkanes can be used to provide evidence for SN1 and SN2 question 1