Elimination reactions

This question is about different ways to make 1,2-dichlorobutane.

Give the name of the mechanism for reaction 1.

State one essential condition needed for reaction 1.

Name of mechanism

Essential condition

Give equations to show three essential steps in the mechanism for reaction 1.

Suggest two reasons why using reaction 1 is likely to give a low yield of 1,2-dichlorobutane.

Give a suitable reagent and conditions needed for reaction 2.

Identify the reagent and name the mechanism for reaction 3.

Name of mechanism

Use of the reagent for reaction 2 followed by the reagent for reaction 3 gives another organic product.

Give the structure of the other organic product.

Each of the conversions shown uses KOH as a reactant.

In which conversion does KOH not act as a base?

Which diagram shows a correct step in the mechanism for an elimination reaction of bromoethane?

A student plans a series of chemical tests to confirm the identities of four organic

This is the student’s method.

To separate test tubes containing samples of each liquid:

Test 1 add potassium dichromate(VI) solution and warm gently

Test 2 add Fehling’s solution and cool in iced water

Test 3 add sodium hydrogencarbonate solution and test any gas produced with a lighted splint

Test 4 add bromine water and shake at room temperature.

Identify the missing reagent needed in Test 1.

In addition to the missing reagent in Test 1, there is a mistake in the method for two of the other tests.

State the two mistakes.

Suggest how each of the mistakes should be corrected.

The missing reagent is added and the mistakes are corrected.

Identify the liquid(s), J, K, L and M, that would react in each test.

State the expected observation for each reaction.

Liquid(s) that react in Test 1

Expected observation

Liquid(s) that react in Test 2

Expected observation

Liquid(s) that react in Test 3

Expected observation

Liquid(s) that react in Test 4

Expected observation

Figure 10 shows the apparatus that is used to separate a mixture of liquids K and M using fractional distillation.

Suggest labels that should be added to positions S, T and U in Figure 10.

Explain why fractional distillation is preferred to simple distillation to separate liquids K and M.

This question is about isomerism and the dehydration of alcohols.

Pentan-2-ol has the molecular formula C₅H₁₂O

Draw the displayed formula of an unbranched position isomer of pentan-2-ol that can be dehydrated to form a single alkene.

Draw the skeletal formula of a chain isomer of pentan-2-ol that can be dehydrated to form a mixture of alkenes.

Draw the structure of an unbranched functional group isomer of pentan-2-ol.

Another isomer of pentan-2-ol is an alcohol that is not dehydrated when heated with concentrated sulfuric acid.

Draw the structure of this isomer.

An incomplete mechanism for the dehydration of a compound is shown.

Complete the mechanism for this reaction by drawing two curly arrows on the intermediate.

Name the mechanism for this reaction.

An isomer of the final product can also form in the reaction in Question 02.5.

Draw the structure of this isomer.

Consider this reaction scheme.

Which step is shown with a correct reagent and a correct condition?

Under suitable conditions, 2-bromobutane reacts with sodium hydroxide to produce a mixture of five products, A, B, C, D and E.

Products A, B and C are alkenes.

A is a structural isomer of B and C.

A does not exhibit stereoisomerism.

B and C are a pair of stereoisomers.

Products D and E are alcohols.

D and E are a pair of enantiomers.

Give the names of the two concurrent mechanisms responsible for the formation of the alkenes and the alcohols.

Mechanism to form alkenes

Mechanism to form alcohols

Define the term stereoisomers.

Deduce the name of isomer A.

Explain why A does not exhibit stereoisomerism.

Outline the mechanism for the reaction of 2-bromobutane with sodium hydroxide to form alkene A.

Deduce the name of isomer B and the name of isomer C.

Explain the origin of the stereoisomerism in B and C.

Draw 3D representations of enantiomers D and E to show how their structures are related.

A student compares the rates of hydrolysis of 1-chlorobutane, 1-bromobutane and 1-iodobutane.

The suggested method is:

• add equal volumes of the three halogenoalkanes to separate test tubes

• add equal volumes of aqueous silver nitrate to each test tube

• record the time taken for a precipitate to appear in each test tube.

State and explain the order in which precipitates appear.

Order in which precipitates appear

Which compound can be dehydrated to form an alkene?

This question is about making a diester from cyclohexanol.

State the type of reaction in step 1.

Give the name of the reagent needed for step 1.

State the reagents needed and give equations for step 2 and step 3.

Show the structure of Compound G in your equations.

Step 2 equation

Step 3 equation

Cyclohexane-1,2-diol reacts with ethanedioyl dichloride.

Give the name of the mechanism for this reaction.

Complete the mechanism to show the formation of one ester link in the first step of this reaction.

Mechanism

Suggest why chemists usually aim to design production methods

• with fewer steps

• with a high percentage atom economy.

High percentage atom economy

A student plans an experiment to investigate the yield of propanoic acid when a sample of propan-1-ol is oxidised.

Figure 4 shows the apparatus that the student plans to use for the experiment.

The student’s teacher says that the apparatus is not safe.

Give two reasons why the apparatus shown in Figure 4 is not safe.

Give one additional reagent that is needed to form any propanoic acid.

State two more mistakes in the way the apparatus is set up in Figure 4.

State the purpose of the small glass beads in the flask in Figure 4.

After correcting the mistakes, the student heats a reaction mixture containing 6.50 g of propan-1-ol with an excess of the oxidising agent. The propanoic acid separated from the reaction mixture has a mass of 3.25 g

State the name of the technique used to separate the propanoic acid from the reaction mixture.

Calculate the percentage yield of propanoic acid.

State the type of reaction in step 1.

Identify the reagent(s) and conditions needed for step 1.

State the name of the mechanism for the reaction in step 2.

Identify the inorganic reagent needed for step 2.

Name the organic product of step 2.

Name of mechanism

Name of organic product

The organic product of step 2 is reacted with concentrated sulfuric acid in step 3.

Outline the mechanism for step 3.

Draw the repeating unit of polystyrene.

A student prepared cyclohexene by heating cyclohexanol with concentrated phosphoric acid. The cyclohexene produced was distilled off from the reaction mixture.

Complete the diagram of the apparatus used to distil the cyclohexene from the reaction mixture at 83 °C.

The distillate was shaken with saturated sodium chloride solution. The cyclohexene was separated from the aqueous solution using a separating funnel.

State why cyclohexene can be separated from the aqueous solution using the separating funnel.

The cyclohexene separated in Question 02.2 was obtained as a cloudy liquid. The student dried this cyclohexene by adding a few lumps of anhydrous calcium chloride and allowing the mixture to stand.

Give one observation that the student made to confirm that the cyclohexene was dry.

In this preparation, the student added an excess of concentrated phosphoric acid to

Calculate the percentage yield of cyclohexene obtained. Give your answer to the appropriate number of significant figures.

Cyclohexene reacts with bromine.

Complete the mechanism for this reaction.

Ethanal reacts with potassium cyanide, followed by dilute acid, to form 2-hydroxypropanenitrile.

Name the mechanism for the reaction between potassium cyanide and ethanal.

The 2-hydroxypropanenitrile formed by the reaction in question 04.1 is a mixture of equal amounts of two isomers.

State the name of this type of mixture.

Explain how the structure of ethanal leads to the formation of two isomers.

Draw 3D representations of the two isomers to show the relationship between them.

3D representations

2-Hydroxypropanenitrile can be used in the synthesis of the monomer,

Suggest a suitable reagent and conditions for the conversion of 2-hydroxypropanenitrile into acrylonitrile.

Draw a section of the polymer polyacrylonitrile, showing three repeating units.

Figure 1 shows some compounds made from a halogenoalkane.

Draw the displayed formula of compound J.

Name the mechanism for Reaction 2 and give an essential condition used to ensure that CH₃CH₂CH₂NH₂ is the major product.

Name of mechanism

Calculate the mass, in grams, of CH₃CH₂CH₂NH₂ produced from 25.2 g of CH₃CH₂CH₂Br in Reaction 2 assuming a 75.0% yield.

Give your answer to the appropriate number of significant figures.

When Reaction 2 is carried out under different conditions, a compound with molecular formula C₉H₂₁N is produced. Draw the skeletal formula of the compound. Identify the functional group in the compound including its classification.

Skeletal formula

Identify the reagent and conditions used in Reaction 3.

Name and outline a mechanism for Reaction 3.

Name of mechanism

Mechanism