E-Z isomerism

How many stereoisomers does the compound CH₃CH(Br)CH=CHCH(Cl)CH₃ have?

A 2

B 4

C 6

D 8

This question is about hydrocarbons with six carbon atoms.

Compound A is a hydrocarbon:

Compound A

What is the systematic name of compound A ?

The table below shows incomplete information about two hydrocarbons.

Complete the table.

Compound B, CH₃CH=C(CH₃)CH₂CH₃, exists as E and Z stereoisomers.

Draw the structures of the E and Z stereoisomers of compound B.

Explain why compound B can form E and Z stereoisomers.

Hexane, C₆H₁₄, is used as a fuel.

1.0 mol of hexane is mixed with 6.0 mol of oxygen and combusted.

Construct an equation for the incomplete combustion of 1.0 mol of hexane with 6.0 mol of oxygen.

Which hydrocarbons are unsaturated?

Which hydrocarbons are alicyclic?

Which hydrocarbons have the general formula C_nH_2n?

What is the systematic name of hydrocarbon C ?

Explain why hydrocarbon D is a Z-stereoisomer.

This question is about unsaturated hydrocarbons.

What is the systematic name of hydrocarbon A ?

Compounds B and C are branched hydrocarbons that are structural isomers of C₆H₁₂.

Compounds B and C both have stereoisomers.

• Compound B has cis and trans isomers but does not have optical isomers.

• Compound C has optical isomers but does not have cis and trans isomers.

What is meant by the term structural isomers ?

What is meant by the term stereoisomers ?

Draw structures for the cis and trans isomers of the branched hydrocarbon B.

Draw 3D structures for the optical isomers of compound C.

Compounds D and E are two more structural isomers of C₆H₁₂.

Compounds D and E do not show stereoisomerism.

Table 16.1 shows NMR and infrared (IR) spectral data for D and E.

Draw the structures of D and E and explain how the spectral data in Table 16.1 provides evidence for the structures.

Draw the structures of the products you would expect from the ozonolysis of the two compounds below.

Which type(s) of stereoisomerism is/are shown by 2,4-dimethylhex-2-ene?

A E / Z isomerism only.

B Optical isomerism only.

C Both E / Z isomerism and optical isomerism.

D Neither E / Z isomerism nor optical isomerism.

But-1-ene, H₂C=CHCH₂CH₃, and buta-1,3-diene, H₂C=CH–CH=CH₂, are unsaturated compounds used to make many organic products.

But-1-ene and buta-1,3-diene have -bonds and -bonds.

How many - and -bonds are in one molecule of buta-1,3-diene?

-bonds:........ -bonds:........

But-1-ene is reacted with hydrogen bromide, forming a mixture of two saturated organic products.

One of the organic products is formed in a much greater quantity than the other organic product.

Explain why one organic product is formed in a much greater quantity than the other organic product.

Buta-1,3-diene is reacted with an excess of hydrogen bromide, forming a mixture of saturated organic products.

How many saturated organic products could be present in this mixture?

A student thought that buta-1,3-diene can show stereoisomerism.

The student drew out skeletal formulae for the stereoisomers of buta-1,3-diene:

Explain the term stereoisomerism.

Explain, with a reason, whether the student is correct or incorrect.

‘Diels-Alder’ reactions are used in the synthesis of many important organic compounds.

The Diels-Alder reaction of buta-1,3-diene with ethene is shown below.

Add curly arrows to the diagram below to complete the mechanism for this Diels-Alder reaction.

Two more Diels-Alder reactions of buta-1,3-diene are shown below.

In the boxes, draw the organic product of each reaction.

What is the name of the compound below?

H₃C CH₂CH₃

A E-3-bromopent-2-ene

B E-3-bromopent-3-ene

C Z-3-bromopent-2-ene

D Z-3-bromopent-3-ene

Which alcohol reacts with an acid catalyst to form a mixture of stereoisomers?

A 3-methylbutan-2-ol

B pentan-1-ol

C 2-methylhexan-2-ol

D heptan-4-ol

This question is about unsaturated aldehydes and alcohols.

Outline the reaction mechanism for the formation of one of the organic products.

Include curly arrows and relevant dipoles.

Explain why one of the organic products forms in a much greater quantity than the other organic product.

Describe how the observations from a chemical test would distinguish between geraniol and citronellal.

What is the molecular formula of geraniol?

Explain why geraniol and citronellal are structural isomers of each other.

Explain the term stereoisomerism.

Dettol ® is a disinfectant containing the antiseptic chloroxylenol, shown below.

Chloroxylenol is a weak Brønsted–Lowry acid.

What is the systematic name of chloroxylenol?

Predict the number of peaks in a¹³C NMR spectrum of chloroxylenol.

Name the functional group responsible for the acidity of chloroxylenol and describe a simple test which would confirm the presence of this group.

Functional group........

Test........

A student measures the pH of the contents in a bottle of Dettol ® as 5.14.

The label on the bottle shows the percentage of chloroxylenol in Dettol ® as 4.80% i.e. 100 cm³ of Dettol^® contains 4.80 g of chloroxylenol.

Assume the following:

• Chloroxylenol is the only acidic component in Dettol ®.

• Chloroxylenol is a weak monobasic acid.

• The density of Dettol ® is 1.00 g cm −3.

Write the equation, using molecular formulae, for the acid dissociation of chloroxylenol.

Calculate the acid dissociation constant, K_a, for chloroxylenol.

K_a =........ mol dm⁻³

Dettol^® contains other chemicals including -terpineol, shown below.

-Terpineol is a chiral compound.

Show with an asterisk, (*), the chiral centre(s) in the structure of -terpineol.

-Terpineol meets the requirements for E / Z isomerism. However, only one E / Z isomer of -terpineol exists.

Explain

• why -terpineol meets the requirements for E / Z isomerism

• whether -terpineol is an E- or Z- isomer

• why only one E / Z isomer of -terpineol exists.

-Terpineol contains two functional groups.

For each functional group, choose a reagent that reacts with that group only. Draw the structures for the organic products of the reactions.

Show structures for organic compounds.

Reagent(s)........

Name of functional group that reacts........

Structure of organic product

Reagent(s)........

Name of functional group that reacts........

Structure of organic product

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 unsaturated hydrocarbons.

Compound A and compound B are isomers.

Compound A has a lower melting point than compound B.

Suggest why.

Compound C, CH₃CH₂CH=CHCH₂CH₂OH, exists as cis and trans stereoisomers.

Name compound C.

Define the term stereoisomers.

Draw the structures of the cis and trans stereoisomers of compound C.

The C=C group in an alkene contains a -bond.

Complete the diagram below to show how p-orbitals are involved in the formation of a -bond.

Compound D, shown below, reacts with hydrogen bromide by electrophilic addition. A mixture of two organic compounds, E and F, is formed.

compound D

Suggest how an HBr molecule can act as an electrophile.

Draw the structures of the two organic compounds E and F.

Outline the mechanism of the reaction between compound D and hydrogen bromide to form either compound E or compound F.

Include curly arrows and relevant dipoles.

Which of E or F is the major organic product?

Explain your answer.

Major organic product........

Explanation........

Myrcene, C₁₀H₁₆, is a naturally occurring hydrocarbon containing more than one carbon-carbon double bond.

Reaction of 204 mg of myrcene with hydrogen gas produces a saturated alkane.

Calculate the volume of hydrogen gas, in cm³ and measured at RTP, needed for this reaction.

Show your working.

-Carotene is a naturally occurring unsaturated hydrocarbon found in carrots. A -carotene molecule contains 40 carbon atoms, has two rings, and a branched chain.

0.0200 mol of -carotene reacts with 5.28 dm³ of hydrogen gas to form a saturated hydrocarbon.

Using molecular formulae, construct a balanced equation for this reaction.

Include relevant calculations and reasoning.

Equation........