2025 H2 Chem P2 Q7: SN1 vs SN2 Halogenoalkanes Solution

Table 7.1 shows the relative rate of reaction for the \(S_N2\) reactions of three bromoalkanes with an excess of iodide ions. The same solvent and temperature are used in each reaction.

State the factor that determines why the \(S_N2\) reactions described in Table 7.1 occur at different rates.

The relative rate of \(S_N1\) hydrolysis reactions of primary, secondary and tertiary chloroalkanes are investigated under the same reaction conditions.

Explain what determines the rate of hydrolysis in these \(S_N1\) reactions.

Predict the order of the rate of hydrolysis for the \(S_N1\) reactions of the chloroalkanes shown in Table 7.2.

Use '1' to represent the fastest rate of hydrolysis, '2' to represent the second fastest rate of hydrolysis and '3' to represent the slowest rate of hydrolysis.

Pure samples of enantiomers are distinguishable by passing a beam of plane-polarised light through each sample. The angle that the plane is rotated is measured.

2-bromooctane and octan-2-ol both exist as pairs of enantiomers. Table 7.3 describes the angle of rotation of plane-polarised light for pure samples of these enantiomers.

A sample of V is added to an excess of \(NaOH(aq)\). When the hydrolysis reaction is complete, a beam of plane-polarised light is passed through the reaction mixture and the plane is rotated by \(z°\).

Complete Table 7.4 to predict the final angle of rotation of plane-polarised light, \(z°\), after complete hydrolysis of V. Give one reason for each of the predicted angles. Assume that the reaction occurs via either \(S_N1\) or \(S_N2\).