ch2 carbon cpd

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CHAPTER 2



ALKANE

Saturated hydrocarbon

Only consist of C-C single

bond Consist of carbon andhydrogen only



BONDING IN HYDROCARBON

Carbon atom

Hydrogen atom

Electron arrangement: 2.4

Has 4 valence electron

Need 4 more electron to achieve

octet electron arrangement

Electron arrangement : 1

Has 1 valence electron

Need 1 more electron to achieve

duplet electron arrangement

CH H

H

H



Definition …

Molecular formula

Formula that shows the actual number of

atoms of each elements present in themolecule

Structural formula

Formula that shows how the atoms in the

molecule are bonded together and by what

type of bonds.



ALKANE

General formula : CnH2n+2

Naming of alkanes

root ending

No. of carbon

atoms

The homologoeus

series : -ane

Example:

Butane

Longestcarbon

chain Family of

the

organiccompound



ROOT NAMEMeth - 1 carbon atom

Eth - 2 carbon atoms

Prop - 3 carbon atoms

But - 4 carbon atomsPent - 5 carbon atoms

Hex - 6 carbon atoms

Hept - 7 carbon atoms

Oct - 8 carbon atomsNon - 9 carbon atoms

Dec - 10 carbon atoms



Methane CH4

Ethane C2H6

Propane C3H8

CH H

H

H

C CH H

H

H

H

H

C C CH H

H H

H

H

HH

Nomenclature /

Molecular formula

No. of C

atoms

Structural

Formula

3 C

2 C

1 C



Butane C4H10 C C C CH H

H

H

H

H

H

H

H

H

Nomenclature /

Molecular formula

No. of C

atoms

Structural

Formula

Hexane C6H14

4 C

6 C



* Low boiling points and melting points because

forces between molecules are weak

CH4 - C4H10 : gas

C5H12 - C17H38 : liquid

C18H38 : solid

a) Melting and Boiling Point

b) Physical State at Room

Temperature

PHYSICAL PROPERTIES



10

The boiling point increases between 20 -30 °Cper -CH2 group.

Boiling points and melting points increase asnumber of carbon atoms per molecule increases.

Then, size of molecules increases (molecularmass increases)

Forces between molecules (Van der Waalsforces) are stronger

More heat energy is needed to overcome theforces

a) Melting and Boiling Point



* Soluble in non polar solvents (organic solvents),

insoluble in water.

• The density of the alkanes increases with increasing

number of carbon atoms,

BUT is less than that of water.

Hence, alkanes form the upper layer in an alkane-

water mixture.

c) Solubility

d) Density

PHYSICAL PROPERTIES



12

Do not conduct electricity because :

alkanes are covalent compounds,

do not have free ions but are

made up of molecules

e) Electrical Conductivity

PHYSICAL PROPERTIES



CHEMICAL PROPERTIES

Combustion reaction

Substitution reaction



ALKENE

unsaturated hydrocarbon

Consist of C-C double

bond Consist of carbon andhydrogen only



ALKENE

General formula : CnH2n

Naming of alkenes

root ending

No. of carbon

atoms

The homologoeus

series : -ene

Example:

Butene

Longestcarbon

chain Family of

the

organiccompound



COMBUSTION

REACTIONS

Complete combustion – sufficient / excess oxygen

Alkene + O2 → CO2 + H2O

Incomplete combustion – insufficient oxygen

Alkene + O2 → CO + H2O



ADDITION REACTIONS

C = C + A B C C

A B



HYDROGENATION

Alkenes + hydrogen gas → alkanes

|

H

C = C H - H C - CH - - H

H

|

H

|

+

H

|

H

|

- HH -|

H

→

Temperature : 180oC and catalyst : nickel



HALOGENATION

Alkenes + halogen → haloalkanes

H

|

|

Br

C = C Br - Br C - CH - - H

H

|

H

|

+

H

|

- HH - |

Br

→

No catalyst or uv light is needed



ADDITION OF HALOGEN

HALIDES

Alkenes + hydrogen halides → haloalkanes

|

Br

C = C H - Br C - CH - - H

H

|

H

|

+

H

|

H

|

- HH - |

H

→



ADDITION OF WATER

Alkenes + steam → alcohol

|

OH

H - OHC = C C - CH - - H

H

|

H

|

+

H

|

H

|

- HH -|

H

→

Temperature : 300oC Pressure : 60 atm and

catalyst : phosporic acid, H3PO4



ADDITION OF

HYDROXYL GROUPS

Alkenes + acidified KMnO4 → diol

|

OH

H2O + [O]|

OH

C = C C - CH - - H

H

|

H

|

+

H

|

H

|

- HH -→



POLYMERIZATION

REACTION

n Alkenes → (alkenes)n

C +

HH

C =

H H

H

C = C+…..

H H

H H

~ C C

H H

H

C

H H

HH

C~

Polymerization of ethene

Temperature : 200oC Pressure : 1200 atm



COMPARING PROPERTIES OF

ALKANES AND ALKENES

Alkanes and alkenes have similar physicalproperties

Physical properties SimilaritiesMelting and boiling

points

both have low melting and boiling points

increase gradually

Physical state changes from gas to liquid to solid

Density both have low densities

Both less dense than water

increase gradually

Solubility insoluble in water but soluble in organic solvents

Electrical conductivity can not conduct electricity in any state



COMPARING PROPERTIES OF

ALKANES AND ALKENES

Alkanes and alkenes have different chemical properties

Chemical properties Differences

Alkanes Alkenes

Reactivity unreactive – saturated

HC

undergo substitution

reaction

reactive – unsaturated

HC

undergo addition

reaction

Reaction with oxygen Burn in air producing

yellow sooty flame

Burn in air producing

yellow and very sootyflame

Reaction with bromine No reaction Decolourise reddish-

brown bromine

Reaction with acidified

KMnO4 solution

No reaction Decolourise purple

acidified KMnO4 solution



HOMOLOGOUS SERIES

A group or family of organic compounds that hasthe following characteristics.

Represented by a general formula

Successive members differ from each other by –CH2

Members can be prepared by similar method Physical properties change regularly

Members have similar chemical properties



FUNCTIONAL GROUP

Special group of atoms attached to an organic molecule.

Determines the chemical properties of the molecule.

Homologous series Functional group

Alkanes -

Alkenes =

Alcohol -OH

Carboxylic acid -COOH

Esters -COO-



HOW TO NAME

ISOMERS?STEP 1 Find the longest continuous carbon

chain in the molecule [root and ending]

STEP 2 Give the name for this longest chainSTEP 3 Number the carbon atoms in this longest

chain beginning at the end nearest tothe first branch

STEP 4 Locate and name the attached alkyl

groups [prefix]STEP 5 complete the name for the molecule by

combining the three component partstogether



HOW TO NAME ISOMERS?

Example

CH3

|CH3 – CH – CH – CH2 – CH2 – CH3

|

CH3

1 2 3 4 5 6

methyl

methyl

ROOT : hex

ENDING : ane

PREFIX : 2,3-dimethyl

2,3-dimethylhexane



Alcohols

Non-hydrocarbons : C, H, O

Functional group : -OH (hydroxyl group)

General formula : CnH2n+1OH



Preparation of alcohol

Fermentation

Hydration



DEHYDRATION REACTION



CARBOXYLIC ACID

General formula : CnH2n+1COOH

Functional group : carboxyl group , -COOH

Naming:

root ending

ch2 carbon cpd

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