Alkane ( Print )

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Homologous Seriesy A series of organic compounds with similar chemical

properties, in which each member differ by CH2 is

called the homologous series.



Homologous

series

General

formula

Example Functional

group

Alkanes CnH2n + 2 CH4

Alkyl CnH2n + 1 CH3

Alkenes CnH2n C2H4 C = C

Alkynes CnH2n í 2 C2H2 C C

Alcohols CnH(2n + 1)OH CH4O - OH

Carboxylic acid CnH2n+1COOH CH2O2 - COOHEster RCOOR¶



Alkanes :

CnH2n+2 , n = 1,2,3,.



Formula Branch or name of group

CH3 - methyl

C2H5 - ethylC3H7 - propyl

C4H9 - butyl

C5H11 - pentyl

A) IUPAC (International Union of Pure and Applied Chemistry)

± is used to name organic compound.

Organic compound is divided into three portions which is Prefix + Root + Suffix.

1.Prefix ± name of the branch or side chain.

General formula: CnH2n+1 ±Where n = 1, 2, 3, « (n = number of carbon)

Alkyl group signifies that it is not part of the main chain.



Number of side chain Prefix

2 Di-

3 Tri-

4 Tetra-

5 Penta-

6 Hexa-

Two or more types of branches are present, name them in

alphabetical order.

More than one side chains are present, prefixes are used.



Number of carbon

atoms

Root name

1 meth-2 eth-3 prop-4 but-

5 pent-6 hex-7 hept-8 oct-9 nan-10 dec-

2.Root ± the parent hydrocarbon (denotes the longest carbon chain).

�The longest continuous (straight chain) carbon chain is selected.

�Identify the number of carbon.



Homologousseries

Functionalgroup

Suffix

Alkane - C C - -ane

Alkene - C = C - -ene

Alcohol OH -olCarboxylic acid COOH -oic

Ester COO -oate

3. Suffix ± f unctional group.

Prefix + Root + Suffix



Naming Alkanesy IUPAC rules :

y Choose the longest continuous carbon chain as the

parent chain. Carbon atoms are numbered startingfrom whichever end that gives the lower value forthe 1st substituent.

y Prefix di-, tri-, tetra,is used to indicate the same

substituents in the molecule.

y Substituents are named in the order of increasingsize or in alphabetical order.



Physical Properties of AlkaneName Molecular

formula

RMM Density

(g cm-3)

Physical state at

25°C

Methane CH4 16 - Gas

Ethane C2H6 30 - Gas

Propane C3H8 44 - Gas

Butane C4H10 58 - Gas

Pentane C5H12 72 0.63 Liquid

Hexane C6H14 86 0.66 Liquid

Heptane C7H16 100 0.68 Liquid

Octane C8H18 114 0.70 Liquid

Nonane C9H20 128 0.72 Liquid

Decane C10H22 142 0.73 Liquid

.



Name Formula Number of isomers

Methane

EthanePropane

Butane

Pentane

Hexane

Heptane

Octane

Nonane

Decane

Undecane

Dodecane

Tridecane

Tetradecane

Pentadecane

Eicosane

CH4

C2H6

C3H8

C4H10

C5H12

C6H14

C7H16

C8H18

C9H20

C10H22

C11

H24

C12H26

C13H28

C14H30

C15H32

C20H42

2

3

5

9

18

35

75

159

355

802

1858

4347

360000

gas

liquid

solid



Physical PropertiesName Physical

StateDensity (g cmí3)

Solubility in water

Electrical conductivity

Methane

Ethane

Propane

Butane

Pentane

Hexane

Heptane

OctaneNonane

Decane

0.63

0.66

0.68

0.700.72

0.73

Insoluble in

water

Cannot

conduct

electricity

gas

liquid



Physical Properties of Alkane.

Solubility in water ± all members in alkanes are insoluble in water but soluble in many organic solvent (benzene and ether ).

Density of alkane ± the density of water is higher than density of

alkane.

When going down the series, relative molecular mass of alkanes is

higher due to the higher force of attraction between molecules and

alkane molecules are packed closer together.

Electrical conductivity ± all members in alkanes do not conduct

electricity.

Alkanes are covalent compounds and do not contain freely moving ions.

Boiling and melting points ± all alkanes in general have low

boiling points and melting points.

Alkanes are held together by weak intermolecular forces.



Chemical properties of Alkane

Reactivity of alkanes

Alkanes are less reactive (saturated hydrocarbon).

Alkanes have strong carbon-carbon (C ± C) bondsand carbon-hydrogen (C ± H) bonds.

All are single bonds which require a lot of energy to

break.

Alkanes do not react with chemicals such as oxidizing agents, reducing agents, acids and

alkalis.



Chemical properties of Alkane

Substitution reaction of alkanes

(Halogenation)

Substitution reaction is one atom (or a group of atoms) in a molecule is replaced by

another atom (or a group of atoms).

Substitution reaction of alkanes take place in

ultraviolet light.



Example:

Alkanes react with bromine vapour (or chlorine) in

the presence of UV light.

CH4 + Cl2 ±> HCl + CH3Cl (Chloromethane)CH3Cl + Cl2 ±> HCl + CH2Cl2 (Dichloromethane)

CH2Cl2 + Cl2 ±> HCl + CHCl3 (Trichloromethane)

CHCl3 + Cl2 ±> HCl + CCl4 (Tetrachloromethane)

The rate of reaction between bromine and alkanes

is slower than the rate of reaction between chlorine

and alkanes



Combustion of Alkanesy Combustion of alkanes

Complete combustion of hydrocarbons

C x H y + ( x + y/4) O2 > x CO2 + y/2 H2OCH4 + 2O2 > CO2 + 2H2O

y Incomplete combustion

occurs when insufficient supply of oxygenCH4 + O2 > C + H2O2CH4 + 3O2 > 2CO + 4H2O



Isomers

Butane, C4H10



( A)

(B)

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