Halogenoalkanes (Edexcel AS Chemistry)

This question concerns halogenoalkanes.

1-chloropropane can react to form organic products as shown in the reaction scheme:

The bromoalkanes, X, Y and Z, were each added to a mixture of aqueous silver nitrate and ethanol at 50°C. The rate of hydrolysis was compared by measuring the time for a precipitate to appear.

The relative rates of hydrolysis are in the order (fastest first)

This question is about halogenoalkanes.

2‐chloro‐2‐methylpropane can be hydrolysed by water.

The equation for this reaction is

(CH₃)₃CCl + H₂O → (CH₃)₃COH + H⁺+ Cl⁻

The graph shows how the concentration of 2‐chloro‐2‐methylpropane changes with time during an investigation of this reaction.

Calculate the rate of reaction at 50s. Show your working on the graph.
Include units with your final answer.

Rate of reaction at 50s = ............................

What is the classification of the mechanism for the hydrolysis of 2‐chloro‐2‐methylpropane by water?

The letters X, Y and Z refer to three different halogenoalkanes:

1 cm³ of each of these halogenoalkanes was added to separate test tubes containing 5 cm³ of ethanol and 5 cm³ of aqueous silver nitrate solution in a water bath at 50 °C.

Under different conditions, 2‐chloro‐2‐methylpropane can react to produce 2‐methylpropene,

(2)

Draw the displayed formula for the repeat unit of a polymer that is made by the polymerisation of 2‐methylpropene, .

(2)

(4)

This is a question about the hydrolysis of halogenoalkanes.

Devise an experiment, giving outline details only, that would enable the relative rates of hydrolysis of halogenoalkanes to be compared.

Explain the trend in the rates of hydrolysis of 1-chlorobutane, 1-bromobutane and 1-iodobutane.

The product of the hydrolysis of 2-bromobutane is butan-2-ol. Both molecules are chiral.

State what is meant by the term chiral, using three-dimensional diagrams of the enantiomers of butan-2-ol to illustrate your answer.

Compare and contrast the mechanism of hydrolysis, using aqueous potassium hydroxide, of the primary halogenoalkane, RCH₂X, with that of the tertiary halogenoalkane, R₃CX.
Include diagrams of any intermediate or transition state.

Curly arrows are not required.

Bromobutanes react with hot ethanolic potassium hydroxide solution to produce gaseous butenes.

Procedure

• 0.0080 mol of liquid 1-bromobutane was injected into a round bottom flask containing hot ethanolic potassium hydroxide.
• After the reaction, the syringe was sealed using a clamp.
• The syringe was then removed from the apparatus and allowed to cool to room temperature (298 K).

Result
The final volume of but-1-ene collected was 22.0 cm³.

State the purpose of the condenser.

Describe a chemical test on the gas in the syringe to identify its functional group.

Include the expected result.

Calculate the percentage of 1-bromobutane which was converted to but-1-ene.
[Molar volume of a gas at r.t.p. = 24 000 cm³ mol^–1]

Before cooling, the volume of but-1-ene in the gas syringe was 24.0 cm³.

Calculate the temperature of the gas in the syringe before it cooled.

[Assume no loss from the gas syringe during cooling, and a constant pressure]

(1)

(3)

Alkene molecules are formed by elimination from 2-bromobutane.

How many isomeric alkene products will be formed in this reaction?