Alkenes (Edexcel International A Level Chemistry): Exam Questions

This question is about the reactions of propene.

Write an equation for the incomplete combustion of one mole of propene to form carbon dioxide, carbon monoxide, carbon and water as the only products. Include state symbols.

State one similarity and one difference that would be seen when propene is mixed with separate samples of acidified potassium manganate(VII) solution and of bromine water.

Propene reacts by addition polymerisation to form poly(propene).

Draw the structure of poly(propene), showing two repeat units.

Propene reacts with bromine monochloride, BrCl, to form 1-bromo-2-chloropropane as the major product.

i) Complete the diagram of bromine monochloride to show the dipole.

(1)

Br — Cl

ii) Draw the mechanism for the formation of 1-bromo-2-chloropropane in this reaction.

Include curly arrows, and relevant lone pairs.

(3)

Propene reacts with steam in the presence of an acid catalyst to form a mixture of the alcohols propan-1-ol and propan-2-ol.

Complete the mechanism for the formation of propan-2-ol, by adding curly arrows. Include the species formed in the final step.

This question is about alkenes. Alkenes contain a carbon to carbon double bond that consists of a σ bond and a π bond.

Complete the diagram to show the areas of electron density for each bond. Label the σ bond and the π bond.

Propene, C₃H₆ , is an alkene. The reagents needed for three reactions of propene are shown.

i) In each box, draw the structure of the organic product of the reaction.

(3)

ii) Propene also reacts with hydrogen bromide, HBr. Give the mechanism for this reaction to form the major product. Include curly arrows, and relevant lone pairs and dipoles.

(3)

Alpha-ocimene contains three carbon to carbon double bonds. It is found in plants and has a sweet smell. The skeletal formula of alpha-ocimene is shown.

i) Give the molecular formula of alpha-ocimene.

(1)

ii) On the skeletal formula, draw a circle around the part of the molecule that gives rise to the geometric isomerism of alpha-ocimene.

(1)

iii) Draw the skeletal formula of the other geometric isomer of alpha-ocimene.

(1)

iv) In an experiment, 0.050 mol of alpha-ocimene reacted with 3.6 dm³ of hydrogen, H₂, in the presence of a catalyst.
Deduce the structure of the product of this reaction.

You must show your working.
[Molar volume of H₂ = 24 dm³ mol⁻¹ ]

(3)

Calculation

Structure

This question is about alkenes.

An alkene has a molar mass of 112 g mol⁻¹.

Deduce the molecular formula of this alkene.

There are a number of different alkenes with the molecular formula C₄H₈.

i) Draw the structure of the branched-chain alkene with the molecular formula C₄H₈.

(1)

ii) Give the structures and names of the two geometric isomers with the molecular formula C₄H₈.

(2)

Two reactions of 1-methylcyclohexene are shown.

i) Draw the skeletal formula of compound X formed in Reaction 1.

(1)

ii) Give the reagent and condition needed for Reaction 2.

(2)

Reagent ....................................................................................

Condition ..................................................................................

Iodine monochloride, ICl, reacts with alkenes in a similar way to hydrogen bromide.

Complete the mechanism for the reaction of iodine monochloride with propene to form the major product. Include curly arrows, the relevant lone pair and the structures of the intermediate and product.

A section of a polymer showing two repeat units is given.

Give the name of the monomer that forms this polymer.

0.0100 mol of an alkene reacts completely with exactly 600 cm³ of hydrogen gas, measured at 298 K and 1.24 × 10⁵ Pa pressure, to form an alkane.

Use the ideal gas equation to deduce the number of double bonds in one molecule of the alkene. You must show your working.

[pV = nRT      R = 8.31 J mol⁻¹ K⁻¹]