CYCLOALKANES

HYDROCARBONS N5CHEMISTRY

N5CHEMISTRY

CYCLOALKANES

CYCLOHEXANE

After completing this topic you should be able to :

HYDROCARBONSCYCLOALKANES

• State the cycloalkanes are another homologous series and write the general formula.

• State the physical and chemical properties of the cycloalkanes.

• Describe how physical properties (melting point, boiling point, rate of evaporation, viscosity) and chemical properties ( flammability and smokiness of flame) relates to the size of molecule.

• Give some uses of cycloalkanes.

N5CHEMISTRY

N5CHEMISTRY

CYCLOALKANESCarbon atoms can join to form RINGS of carbons. The smallest ring contains 3 carbons.

The simplest molecule is called CYCLOPROPANE.

C

H

C

C

HH

HH

Hfull structural formula

C3H6molecular formula

CYCLOPROPANE

Carbons atoms are joined in a ring.

Molecule has 3 carbon atoms.

All the carbon to carbon bonds are single (C-C).

shortened structuralformula

Write the names, full structural formulae, shortened structural formula and molecular formula of each cycloalkane with 4 to 6 carbon atoms.

GENERAL FORMULA FOR CYCLOALKANES

CnH2nn = 3, 4, 5, ……….

H

C

C C

C

H

HH

H

H H

H

H

C

C

C

C H

H

H

H

H

HH

C

H

HH

C

C

C

C H

H

H

H

H

HH

CH

H

C

HH

cyclobutane

C5H10

cyclohexane

C4H8

cyclopentane

C6H12

PROPERTIES OF CYCLOALKANESThe structure of cycloalkanes are similar to alkanes i.e. they all contain C-C. This means cycloalkanes are saturated hydrocarbons.

PROPERTY TESTED CYCLOHEXANE

Appearance (colour and state)

Smell

Flammability

Solubilty in water

pH (acidic / neutral / alkaline?)

Effect on bromine solution

Colourless liquid

Strong

Very flammable smokey flame

Immiscible

Neutral

Remains orange

Cycloalkanes have similar properties to alkanes.

Write the WORD and BALANCED FORMULA EQUATION for the combustion of cyclohexane.

cyclohexane oxygen water carbondioxide

+ +

++C6H12 O2 H2O CO2669

Cycloalkanes are another HOMOLOGOUS SERIES.

HOMOLOGOUS SERIES & PHYSICAL PROPERTIES

The physical properties of the molecules in a homologous series all change as the number of carbon atoms in the molecules increase.

The melting and boiling points, the viscosity of the alkanes, alkenes and cycloalkanes all show an increase going up the series as the number of carbon atoms in their molecules increase.

HYDROCARBONS

ALKANES ALKENES CYCLOALKANES

1. Flammable - all produce H2O + CO2

2. Immiscible in H2O

3. pH = neutral (7)

4. Bromine solution.No immediateeffect.

General FormulaCnH2n + 2

General FormulaCnH2n

General FormulaCnH2n

1. Flammable - all produce H2O + CO2

2. Immiscible in H2O

3. pH = neutral (7)

4. Bromine solution.No immediateeffect.

1. Flammable - all produce H2O + CO2

2. Immiscible in H2O

3. pH = neutral (7)

4. Bromine solution.Immediately decoloursises