ALKANA

CHAPTER 2

CARBON
COMPOUND

Definition :
Compounds that contain the element carbon

CARBON COMPOUNDS

Organic compound Inorganic compound

Hydrocarbon Non-hydrocarbon

Organic Compounds

• Carbon containing compounds
(carbon bonded with other element by covalent
bond)

• Found : living things OR derived from living things
• Complete combustion : produce CO2 and H2O

• E.g :

Glucose

C6H12O6 (S) + 6O2 (g) 6CO2(g) + 6H2O (l)

Inorganic Compounds

• Generally without carbon atoms and
mainly substance from non-living things

• Found : rocks, minerals, synthesized by
human being

• Alkalis, bases, salts and mineral acids
• However :

Some compound contain carbon element.
E.g : CO2 (carbon dioxide)

Hydrocarbon

DEFINITION
Simplest of all organic compounds
Containing : Hydrogen and Carbon only

Saturated Unsaturated

HH C–C C–C

H C–C–H Double Bond Triple Bond
(Alkenes) (Alkynes)
HH
Single Bond (Alkanes)

Non-hydrocarbon

-Contain Carbon (C) Hydrogen (H) and other elements

-some OR all hydrogen atom have been replaced :

(a) Oxygen (b) halogens

(c) Phosphorus (d) Nitrogen

Alcohols Carboxylic acids Esters Polymers

HH HO HO H

H C – C – OH H C – C – OH H C – C – O – C – H

HH HH H H

Ethanol Ethanoic acid Methyl Ethanoate

ALKANES

vWhat is an alkanes?
vFormulae for organic molecules

vNaming alkanes
vPhysical Properties of alkanes
vChemical Properties of alkanes

ALKANES

• Family of hydrocarbon
• Saturated hydrocarbon (each carbon atom

is bonded to 4 other atom) by single
covalent bond

HHH

H C–C–C H

HHH

Propane C3H8

Formulae for organic molecules

• Molecular formulae only shows about :
(a) actual numbers atoms present in molecule
(b) types of atoms present in molecule

• Nothing tells us : how the atoms are bonded to
each other

• Structural formula : shows how the atoms in a
molecule are bonded together and by what
types of bonds

General Formula & Naming

• CnH2n+2

where n = number of carbon atom
• IUPAC : 2 component

Root Ending

Denotes the longest Denotes the family of the

carbon chain Organic compound

Prefix + Root + Suffix

Steps : Naming Organic Compounds

(1) Identify the parent hydrocarbon (Root)
(a) Select the longest continuous carbon chain that
contains functional group

(2) Identify and indicate the position of functional group (Suffix)
(a) gives the functional group the lowest possible numbers
(b) if the chain forms a ring, the name preceded by cyclo-

(3) Name the branch or side-chain (Prefix)
(a) Alkyl group are named by replacing the ‘ane’ suffix of
alkene with ‘yl’ (not part of the main chain)
(b) If more than one side chains are present, prefixes like
Di-, Tri-, Tetra- are used
(c) If 2 or more types of branches are present, name them
in alphabetical order

Step 1 : Identify the parent hydrocarbon
(Root)

No. of Code No. of Code
Carbon Letters Carbon Letters

1 meth 6 hex

2 eth 7 hept

3 prop 8 oct

4 but 9 nan

5 pent 10 dec

Step 2 : Identify and indicate the position of
functional group (Suffix)

Homologous Functional Suffix
series group
-ane
alkane C–C–

alkene C–C– -ene

alcohol OH -ol

carboxylic O -oic
acid C – OH -oate
C–O
ester O

Step 3 : Name the branch OR side-chain
(Prefix)

Formula Branch or No. of Code
name of group side-chain Letters

CH3 methyl 2 Di –

C2H5 ethyl 3 Tri –

C3H7 propyl 4 Tetra –

C4H9 Butyl 5 Penta –

C5H11 pentyl 6 Hexa –

EXAMPL
E

CH3

CH3 – CH – CH – CH2 – CH2 – CH3

CH2 – CH3
CH2 – CH – CH – CH2 – CH3

CH3

Electrical conductivity Density

vCannot conduct electricity vLess dense than water

Physical Properties
Of Alkanes

Solubility

vDesolve in organic Melting and boiling points

solvents vLow melting and boiling

vInsoluble in water points

Physical Properties of Alkanes

Name Molecular RMM Density Physical
Formula (g cm-3) State at
16
Methane CH4 30 - 25 C
Ethane C2H6 44 - Gas
Propane C3H8 58 -
Butane C4H10 72 - Liquid
Pentane C5H12 86 0.626
Hexane C6H14 100 0.659
Heptane C7H16 114 0.684
Octane C8H18 128 0.703
Nonane C9H20 142 0.718
Decane C10H22 0.730

Physical Properties of Alkanes

Name Number of Melting Boiling
carbon point Point
atom (0C) (0C)
-162
Methane 1 -182 -89
Ethane 2 -183 -42
Propane 3 -188
Butane 4 -138 -1
Pentane 5 -130 36
Hexane 6 -95 69

Heptane 7 -91 98
Octane 8 -57 126
Nonane 9 -54 151
Decane 10 -30 174

Density of water>density of alkane

When going down the series :
• RMM of alkanes increase
• Force of attraction between molecules

increase
• Alkane molecules are packed closer

together

Electrical Conductivity

vAlkanes do not conduct electricity as they
are covalent compounds that consist of
molecules and DO NOT contain freely
moving ions

Boiling and melting point increase

When going down the series :
• Size of molecules increase
• Force of attraction between molecules

(weak Van der Waals’ force) increase
• More energy required to overcome the

attraction

Solubility

• All members of the alkanes series are
insoluble in water

• However, they are soluble in many organic
solvent such as ether and benzene

Chemical Properties of Alkanes

• Reactivity of alkanes
• Combustion
• Substitution reaction of alkanes

(halogenation)

(a) Reactivity of alkanes

• Alkanes are saturated hydrocarbon that are less
reactive than unsaturated hydrocarbons

• Have strong (C – C)bond and (C – H) bonds.
• These single bonds are unreactive and require a

lot of energy to break
• Under ordinary conditions OR at room

temperature, alkanes do not react with
chemicals such as oxidising agents, reducing
agents, acids and alkalis

Combustion of alkanes

• General equation of complete combustion

CxHy + (x + y/4) O2 xCO2 + y/2 (H2O)

• E.g :

CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (l)

• Incomplete combustion of alkanes occurs
when there is insufficient supply of oxygen
OR air

CH4 (g) + O2 (g) C (g) + 2H2O (l)

OR

2CH4 (g) + 3O2 (g) 2CO (g) + 4H2O (l)

Substitution Reaction (Halogenation)

• General equation of substitution reaction

R + Halogen (g) uv R Halogen + H Halogen

• E.g :

CH4 (g) + Cl2 (g) uv CH3Cl (g) + HCl (g)

• Occurs when one atom OR a group of
atom in a molecule is replaced by another
atom (OR a group of atom)

• Readily takes place in a sunlight
• Also can use bromine vapour (Br)

ALKENES

vWhat is an alkanes?
vNaming alkanes

vPhysical Properties of alkanes
vChemical Properties of alkanes

ALKENES

• Family of hydrocarbon containing at least one
carbon-carbon (C – C) double bond

• Unsaturated hydrocarbon (each carbon atom is
bonded to 4 other atom) that contain at least one
double bond

H

H C–C–C H

HHH

Propene C3H6

General Formula & Naming

• CnH2n

where n = number of carbon atom
• IUPAC : 2 component

Root Ending
Denotes the longest Denotes the family of
the and the position of
carbon chain
containing the the double bond
double bond

Prefix + Root + Suffix

Physical Properties of Alkenes

Name Molecular RMM Density Physical
Formula (g cm-3) State at
28 25 0C
Ethene C2H4 42 0.0011
Propene C3H6 56 0.0018 Gas
Butene C4H8 70 0.0023
Pentene C5H10 84 0.6430 Liquid
Hexene C6H12 98 0.6750
Heptene C7H14 112 0.6980
Octene C8H16 126 0.7160
Nonene C9H18 140 0.7310
Decene C10H20 0.7430

Physical Properties of Alkenes

Name Number of Melting Boiling Physical
carbon point Point State at
Ethene atom (0C) (0C) 25 0C
Propene -103
Butene 2 -169 -48 Gas
Pentene 3 -185
Hexene 4 -185 -6 Liquid
Heptene 5 -165 30
Octene 6 -140 64
Nonene 7 -119 93
Decene 8 -104 122
9 -94 146
10 -87 171

Electrical conductivity Density

vCannot conduct electricity vLess dense than water

Physical Properties
Of Alkenes

Solubility

vDesolve in organic Melting and boiling points

solvents (e.g benzene) vDepends on forces of

vInsoluble in water attraction

(float in water)

Density of water>density of alkene

When going down the series :
• RMM of alkenes increase
• Force of attraction between molecules

increase
• Alkene molecules are packed closer

together
• Density increase

Electrical Conductivity

vAlkenes do not conduct electricity as they
are covalent compounds that consist of
molecules and DO NOT contain freely
moving ions

Boiling and melting point increase

When going down the series :
• Size of molecules increase
• Force of attraction between molecules

(weak Van der Waals’ force) increase
• More energy required to overcome the

attraction
• Melting and boiling point increase

Solubility

• Insoluble in water (float on water)
Reason :

Density of water > density of alkene
alkenes

water

• However, they are soluble in many organic
solvent such as ether and benzene

Chemical Properties of Alkenes

• Combustion (reaction with oxygen) Addition
• Polymerisation Reaction
• Hydrogenation ( + Hydrogen)
• Hydration (+ water)
• Halogenation (+ halogen element)
• Hydrogen halides (HX)
• KMnO4 (accidified)

Addition Reaction Of Alkenes
Is a reaction in which atoms or groups of atoms
are added to an unsaturated organic compound
to form a single product which is saturated

Combustion

• Burn with sootier flames than alkanes
• This is because the percentage of carbon

in alkene molecules is higher than that of
alkane molecules
• Burn in plenty of oxygen to produce CO2
and H2O

Combustion of alkanes

• General equation of complete combustion

CxHy + (x + y/4) O2 xCO2 + y/2 (H2O)

• E.g :

C2H4 (g) + 3O2 (g) 2CO2 (g) + 2H2O (l)

• Incomplete combustion of alkenes occurs

when there is insufficient supply of oxygen

OR air

C2H4 (g) + O2 (g) 2C (s) + 2H2O (l) More
OR smooky

C2H4 (g) + 2O2 (g) 2CO (s) + 2H2O (l)

Polymerisation

• Polymers are substances that contain many monomers
which are bonded together in a repeating sequence

• Polymerisation is a process in which small molecules
(monomers) are joined together to form a long chain
(polymers)

• Addition polymerisation : polymerisation of alkene is an
addition reaction

• E.g :

nCH2 CH2 (g) ( CH2 (g) – CH2 )n

polymerisation

Ethene monomers

H HH HH HH HH H
C
More CC CC CC CC C More
ethenes ethenes

H HH HH HH HH H

High Temperature and pressure

H HH HH HH H H H

More C CC CC CC CC C More
chains H HH HH HH HH chains

H

Polyethene polymer (long-chain saturated compound)

The suitable conditions for the
polymerisation of alkenes

(1) At 60-1000C and 7-10 atmosphere with
Ziegler catalyst :

v High density polyethene will be produced

(2) At 200 0C and 1500-2000 atmosphere
without a catalyst

v Low density polyethene will be produced

Hydrogenation

CnH2n + H2 (g) CnH2n+2

Alkene Alkane

Nickel or platinum catalyst
2000C

Eg :

C2H4 (g) + H2 (g) C2H6 (g)

Ethene Nickel Ethane
2000C

Margarine is produced from the hydrogenation of vegetable oils

Hydration (Addition of Water)

(1) Alkenes do not react with water under
ordinary conditions

(2) When a mixture of alkene and steam is
passed over a catalyst, a water molecule
is incorporated into C – C double bond to
produce an alcohol

Hydration

Alkene CnH2n + H2O (g) CnH2n+1 + OH

Phosphoric acid, H3PO4 Alcohol
3000C, 60 atm
C2H5OH (aq)
Eg : C2H4 (g) + H2O (g)

Ethene Steam Ethanol

Phosphoric acid, H3PO4
3000C, 60 atm

Halogenation

CnH2n + Halogen Dihaloalkane
C2H4Br2 (l)
Alkene
Eg :

C2H4 (g) + Br2 (l)

Ethene Bromine 1,2-dibromoethane

vThe brown colour of bromine decolourised immediately to produce a
colourless organic liquid

vBromination can be used to identify an unsaturated organic compound
in a chemical test

Addition of hydrogen Halides

CnH2n + HX Haloalkane

Alkene C2H5Br (g)
Eg :

C2H4 (g) + HBr (g)

Ethene Hygrogen Bromoethane
Bromine

vReaction occurs rapidly at room temperature without catalyst

Cyral Carbon

• Carbon bonded with four (4) different alkyl
group (priorities given to alkyl group rather
than hydrogen atom)

R

RC R

R

Where,
R represent an alkyl group

HH
+H C C C H
H Br

HH Hydrogen Bromide

Cyral Carbon

HHH HHH

H CCCH H CCCH

Br H H H Br H

1-bromopropane Major 2-bromopropane
Produc

t

Addition of Accidified Potassium
Manganate (VII), KMnO4

(1) Accidified potassium manganate (VII)
solution is produced by mixing a
potassium manganate (VII) solution with
dilute sulphuric acid H2SO4