Alkana

Alkanes1.General Formula : CnH2n+2 (number of atoms, n = 1,2,3......)

2.They are saturated hydrocarbons;

each carbon atom is bonded to four other atoms by

single covalent bonds.

3.The members of the family, ending with name ane.

Number of carbon atoms (n)NameMolecular formulaCnH2n+2Molar mass

(g mol-1)Physical state at room temperature

1MethaneC1H2x1+2 = CH416Gas

2EthaneC2H2x2+2 = C2H630Gas

3PropaneC3H2x3+2 = C3H844Gas

4ButaneC4H2x4+2 = C4H1058Gas

5PentaneC5H2x5+2 = C5H1272Liquid

6HexaneC6H2x6+2 = C6H1486Liquid

7HeptaneC7H2x7+2 = C7H16100Liquid

8OctaneC8H2x8+2 = C8H18114Liquid

9NonaneC9H2x9+2 = C9H20128Liquid

10DecaneC10H2x10+2 = C10H22142Liquid

4.Structural formulae of alkanesNameNo. of isomersStructural formulae and Name

Methane

CH40

Ethane,

C2H60

Propane,

C3H80

Butane,

C4H102

Pentane,

C5H123

Hexane,

C6H145

Physical Properties

Physical properties of alkanes

i. cannot conduct electrity

ii. less dense than water

iii. dissolve in organic solvents, insoluble in water

iv. low melting and boiling points

Conclusion:

- molecule held together by weak intermolecular forces

- properties of covalent compound

- gradually steady increase as the number of carbon in alkane

increases6. Steps to name branched alkanes;

i. determined and named the long chains

ii. determined and named the branch chain(CH3

: methyl

(C2H5OR(CH2CH3

: ethyl

(C3H7OR(CH2CH2CH3: prophyliii. give number to the carbon atoms in long chain, which started from the nearest branched

iv. The number for carbon atom which branched emerged from, must put before/infront the alkyl

v. Named the branched first, followed by the named of long chains

The word di, tri is used if the branched chains is more than one Chemical PropertiesReactivity of alkanes1.Not reactive/unreactive because saturated hydrocarbon2.Did not decolourized purple solution of acidified potassium manganate(VII)3.Did not decolourized reddish brown solution of bromine water

4.Neutral.

Combustion of alkanes1.In the presence of sufficient oxygen, alkanes burns to form carbon dioxide and water. complete combustion

Chemical equation:

i. CH4 + 2O2 ( CO2 + 2H2O

ii. C2H6 + 7/2 O2 ( 2CO2 + 3H2O iii. C4H10 + 13/2 O2 ( 4CO2 + 5H2Oiv. C6H14 + 19/2 O2 ( 6CO2 + 7H2O2. If there is insufficient oxygen, carbon monoxide or carbon may be formed incomplete combustion

i. CH4 + 3/2 O2 ( CO + 2H2O

2CH4 + 3 O2 ( 2CO + 4H2O

ii. CH4 + O2 ( C + 2H2OHalogenation

1. The reaction is between alkane dan chlorine.

2. Takes place under sunlight/ultra violet light.

3. Carbon-hydrogen bonds broken and new carbon-halogen bonds

are formed. One or more hydrogen atoms in alkanes molecule may be subtituted by halogen. 4. Halogenation is substitution reaction.

Chlorination of methane

First stage;

Second stage;

Third stage ;

Fourth stage;

Overall equation/chemical equation CH4 + 4Cl2 ( CCl4 + 4HCl

H

H C H

H

H H

H C C H

H H

H H H

H C C C H

H H H

H H H H

H C C C C H

H H H H

n-butane

2 - methyl propane

H H H

H C C C H

H HCH H

H

H H H H H

H C C C C C H

H H H H H

n-pentane

H H H H

H C C C C H

H HCH H H

H

2-methyl butane

H

H H C H H

H C C C H

H HCH H

H

2,2-dimetyl propane

H H H H H H

H C C C C C C H

H H H H H H

n-hexane

H H H H H

H C C C C C H

H HCH H H H

H

2 - methyl pentane

H

H H C H H H

H C C C C H

H HCH H H

H

2,2 - dimethyl butane

2,3 - dimethyl butane

H H H H H

H C C C C C H

H H HCH H H

H

3 - methyl pentane

H

H H H CH H

H C C C C H

H HCH H H

H

H H

|

H C H +Cl-Cl H C Cl + HCl

|

H H monochloromethane

H Cl

|

H C Cl + Cl2 H C Cl + HCl

|

H H dichloromethane

Cl Cl

|

H C Cl + Cl2 H C Cl + HCl

|

H Cl trichloromethane

Cl Cl

|

H C Cl + Cl2 Cl C Cl + HCl

|

Cl Cl tetrachloromethane

Alumina, Al2O3

C9H20 (ce) ( C2H6 (g) + C7H14 (g)

Panas

Nonana Etana Heptena

Alumina, Al2O3

C9H20 (ce) ( C2H6 (g) + C7H14 (g)

Panas

Nonana Etana Heptena