Carbon–carbon bond formation

This question is about reactions of haloalkanes.

Haloalkanes can react with potassium cyanide to form new carbon–carbon bonds.

Outline the mechanism for the reaction of 2-bromopropane with cyanide ions.

Show curly arrows, relevant dipoles and products.

Name this type of mechanism.

The table below shows the boiling points of propan-1-ol and 1-bromopropane.

Propan-1-ol can be reacted to form 1-bromopropane.

Suggest suitable reagents for this reaction.

The reaction to form 1-bromopropane from propan-1-ol is carried out in a flask.

After the reaction, the flask contains a mixture of an organic layer (density = 1.35 g cm^–3) and an aqueous layer (1.04 g cm^–3).

Describe how to obtain pure 1-bromopropane from the mixture.

This question is about carbonyl compounds.

The three compounds below each contain a ketone and one other functional group.

Pyruvic acid
Methylglyoxal
Acetol

What is a functional group ?

A chemical test is carried out which gives a positive result for all three compounds.

Suggest the reagent and observation of this chemical test.

Reagent........

Observation........

A student is provided with three unlabelled sample tubes, containing either pyruvic acid, methylglyoxal or acetol.

The student carries out three chemical tests on each sample.

Complete the table with the expected observations, including ‘no change’ where appropriate.

Complete the flowchart for the reactions of pyruvic acid.

This question is about haloalkanes.

Haloalkanes can be synthesised by reacting alkanes with halogens in the presence of ultraviolet radiation.

An alkane reacts with bromine to form 2-bromo-2-methylpropane.

Write the equation for this reaction, showing the structures of the organic compounds.

Name the reaction mechanism and the type of bond fission that occurs.

Equation

Name of reaction mechanism........

Type of bond fission........

Describe two limitations of the synthesis of 2-bromo-2-methylpropane from an alkane and bromine.

Which compound(s) is/are hydrolysed by HC l (aq) to produce butanoic acid?

1 CH₃CH₂CH₂COOCH₃

2 CH₃CH₂CH₂CH₂CN

3 CH₃CH₂CH₂CH₂Cl

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

This question is about compounds that contain the carboxylic acid functional group.

Carboxylic acids react with alkalis, metals and carbonates to form salts.

Write full equations for the following three reactions. Show structures for organic compounds.

• the reaction of propanoic acid with aqueous potassium hydroxide:

• the reaction of aqueous methanoic acid with magnesium:

• the reaction of the –amino acid, aspartic acid (R=CH₂COOH), with an excess of aqueous sodium carbonate, Na₂CO₃:

This part is about polymers derived from carboxylic acid monomers.

Poly(pent-3-enoic acid) is an addition polymer.

Draw the structure of pent-3-enoic acid and two repeat units of this polymer.

Butanedicarboxylic acid and 1,4-dihydroxy-2-methylbenzene react to form a condensation polymer.

Draw one repeat unit of this condensation polymer.

Three repeat units of a condensation polymer are shown below.

Draw the structure of the monomer required to form this polymer.

A polymer is formed from 400 molecules of 2-aminopropanoic acid.

Draw one repeat unit of this polymer.

What is the relative molecular mass, M_r, of the polymer?

21* Carbon-carbon bond formation is used in synthesis to increase the length of a carbon chain.

Describe the formation of carbon–carbon bonds in aliphatic compounds by two different mechanisms.

Your answer should include mechanisms for each aliphatic compound.

Which reaction is not a reduction?

This question is about organic synthesis.

Prenal, shown below, is used in the synthesis of some pharmaceuticals.

What is the systematic name for prenal?

* A student intends to synthesise compound A using the two-stage route below.

(chloromethyl)benzene Compound A

Plan a two-stage synthesis to prepare 5.44 g of compound A starting from (chloromethyl)benzene, C₆H₅CH₂Cl. Assume that the overall percentage yield of compound A from (chloromethyl)benzene is 25%.

In your answer, include the mass of C₆H₅CH₂Cl required, reagents, and equations where appropriate.

Purification details are not required.

Which of the following reactions produce propan-1-ol?

1 The alkaline hydrolysis of 1-chloropropane.

2 The acid hydrolysis of propyl methanoate.

3 The acid hydrolysis of propanenitrile.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

This question is about benzene.

Over time, the Kekulé and delocalised models have been used to describe the bonding and structure of a benzene molecule.

Describe, in terms of orbital overlap, the similarities and differences between the bonding in the Kekulé model and the delocalised model of benzene.

Experimental evidence led to the general acceptance of the delocalised model over the Kekulé model.

Describe two pieces of evidence to support the delocalised model of benzene.

Benzene can be used as the starting material for the synthesis of compounds D and E, shown below.

In the diagrams C₆H₅ is a phenyl group.

Compounds D and E can be converted into polymers.

Draw two repeat units of these polymers.

Two repeat units of polymer formed from D

Two repeat units of polymer formed from E

State the type of polymer formed from compounds D and E.

From compound D........

From compound E........

In the synthesis of compounds D and E, benzene is first reacted with ethanoyl chloride, CH₃COCl, to form phenylethanone, shown below.

The reaction takes place in the presence of aluminium chloride, Al Cl₃, which acts as a catalyst.

In the mechanism for this reaction,

• ethanoyl chloride first reacts with aluminium chloride to form the CH₃–C⁺=O cation

• the CH₃–C⁺=O cation then behaves as an electrophile.

Complete the mechanism for the reaction.

Include equations to show the role of the Al Cl₃ catalyst, relevant curly arrows and the structure of the intermediate.

Formation of electrophile........

Regeneration of catalyst........

Complete the flowchart for the synthesis of compounds D and E from phenylethanone.

Which of the following could react with the compound below to form a carbon–carbon bond?

2 KCN in ethanol

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Cinnamaldehyde and methylcinnamaldehyde are naturally occurring organic compounds.

Methylcinnamaldehyde is an E stereoisomer.

Explain this statement in terms of the Cahn-Ingold-Prelog (CIP) rules.

A student plans to carry out some chemical tests on both cinnamaldehyde and methylcinnamaldehyde.

Suggest a suitable chemical test to confirm that both compounds contain an unsaturated carbon chain.

Your answer should include the reagent and observations.

Describe a chemical test to confirm that both compounds contain an aldehyde functional group.

Your answer should include the reagent and observations.

Describe a chemical test to confirm that cinnamaldehyde and methylcinnamaldehyde contain a carbonyl group.

How could the products of this test be used to distinguish between the two compounds?

Your answer should not include spectroscopy.

This question is about organic compounds containing nitrogen.

Sodium cyanide, NaCN, can be reacted with many organic compounds to increase the length of a carbon chain.

1-Chloropropane, CH₃CH₂CH₂Cl, reacts with ethanolic sodium cyanide by nucleophilic substitution.

Outline the mechanism for this reaction.

Include curly arrows, relevant dipoles and the structure of the organic product.

Compound G is used to synthesise compounds H and I as shown in the flowchart below.

Complete the flowchart showing the structure of compound G and the formulae of the reagents for Reaction 2 and Reaction 3.

Compound H reacts with dilute hydrochloric acid to form a salt.

Explain why compound H can react with dilute hydrochloric acid and suggest a structure for the salt formed.

Explanation........

Structure

Compound I is the monomer for the biodegradable polymer J.

Draw two repeat units of polymer J and suggest a reason why it is biodegradable.

The repeat unit of Nylon 6,6 is shown below.

Draw the structures of two monomers that can be used to form Nylon 6,6.

A sample of Nylon 6,6 has a relative molecular mass of 21500.

Estimate the number of repeat units in the sample.

Give your answer as a whole number.