Alkane Part 1

8/3/2019 Alkane Part 1

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Alkanes



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1: Classification of Hydrocarbons

1.Alkanes are saturated hydrocarbons:

CH H

H

H

C C CH H

H H

H

H

HH

y saturated (only single C-C bonds)

y hydrocarbon (only C and H)



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Carbon and hydrogen atoms can bond to eachother to form v ery extensiv e and molecularsystems.

2: Bondings in hydrocarbon

Carbon atoms has 4 v alence electrons @ need 4 electrons to reach octet

electron arrangement.@ four bonds to each carbon atom

Hydrogen atoms has 1 v alence electron@ need 1 electron to reach duplet

electron arrangement.@

one bond to each hydrogen atom



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3: Molecular Formulas of Alkanes

Write the molecular formula for each of thealkanes below.

C CH H

H

H

H

H

C CH H

H

H

H

H

C C C CH H

H

H

H

H

H

H

H

H

C C C CH H

H

H

H

H

H

H

H

H

C2H6 C4H10



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6

C5H12

C6H14



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What is the general molecular formula for

alkanes?

Alkanes hav e the general formula

CnH2n+2

n = no.ofcarbon atoms in the molecule



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4: Nomenclature of Alkanes

1. The name of alkanes consist of 2 parts :the stem & the suffix

2. Stem tells the number of carbon atoms

3. Suffix tells the group is alkane: -ane4. Prefix is added to the beginning of the

stem ² tells the number of carbon atoms



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Naming Alkanes

Example : Butane

Name of

alkane

Prefix Suffix

Butane But (no of

carbon atoms

= 4)

-ane (the group

is alkane)



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Meth - 1 carbon atomEth - 2 carbon atomsProp - 3 carbon atoms

But - 4 carbon atomsPent - 5 carbon atomsHex - 6 carbon atomsHept - 7 carbon atoms

Oct - 8 carbon atomsNon - 9 carbon atomsDec - 10 carbon atoms

PrefixesPrefixes



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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 : gasC5H12 - C17H38 : liquidu C18H38 : solid

a) Melting and Boiling Point

b) Physical State at Room T emperature

5: Physical Properties5: Physical Properties



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* Soluble in non polar solv ents (organic

solv ents), insoluble in water.

* The density of the alkanes increaseswith 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



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Do not conduct electricity

because :

alkanes are cov alent compounds, do not hav e free ions but are

made up of molecules

e) Electrical Conductiv ity



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

Boiling points and melting points increase as number of carbon atoms

per molecule increases. Then, size of molecules increases

(molecular mass increases)

Forces between molecules (v an derWaals forces) are stronger

More heat energy is needed to

ov ercome the forces




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Alkane Part 1

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