ch2 carbon cpd

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CHAPTER 2

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 ALKANE

Saturated hydrocarbon

Only consist of C-C single

bond Consist of carbon andhydrogen only

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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

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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.

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 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

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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

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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

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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

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* 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

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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

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* 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

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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

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CHEMICAL PROPERTIES

Combustion reaction

Substitution reaction

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 ALKENE

unsaturated hydrocarbon

Consist of C-C double

bond Consist of carbon andhydrogen only

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 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

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COMBUSTION

REACTIONS

Complete combustion – sufficient / excess oxygen

 Alkene + O2 → CO2 + H2O

Incomplete combustion – insufficient oxygen

 Alkene + O2 → CO + H2O

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 ADDITION REACTIONS

C = C + A B C C 

A B 

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HYDROGENATION

 Alkenes + hydrogen gas → alkanes 

|

H

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

H

|

H

|

+

H

|

H

|

- HH -|

H

→ 

Temperature : 180oC and catalyst : nickel

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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

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 ADDITION OF HALOGEN

HALIDES

 Alkenes + hydrogen halides → haloalkanes 

|

Br

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

H

|

H

|

+

H

|

H

|

- HH - |

H

→ 

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 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

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 ADDITION OF

HYDROXYL GROUPS

 Alkenes + acidified KMnO4 → diol 

|

OH

H2O + [O]|

OH

C = C C - CH - - H

H

|

H

|

+

H

|

H

|

- HH -→ 

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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

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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

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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

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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

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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-

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ISOMERS

Molecules with the same molecular formula

but different structural formula

H – C – C – C – C – H

H H H H

| | | |

| | | |H H H H

H|

H – C – H

H H| |

H – C – C – C – H| | |H H H

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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

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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

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Alcohols

Non-hydrocarbons : C, H, O

Functional group : -OH (hydroxyl group)

General formula : CnH2n+1OH

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  H

|

H – C – H

|

O – H

H H

| |

H – C – C – H

| |

H O – H

H H H

| | |

H – C – C – C – H

| | |

H H O – H

H H H H

| | | |

H – C – C – C – C – H

| | | |

H H H O – H

CH3OH

methanol

C3H7OH

Propan-1-ol

C2H5OH

ethanol

C4H9OH

Butan-1-ol

 Alcohols

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Preparation of alcohol

Fermentation

Hydration

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DEHYDRATION REACTION

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CARBOXYLIC ACID

General formula : CnH2n+1COOH

Functional group : carboxyl group , -COOH

Naming:

root ending