Download Homologous Series

Organic
Chemistry
Lesson 1
Homologous Series
We Are Here
Lesson 1: Homologous Series

Objectives:

Reflect on previous knowledge of organic chemistry

Understand the term ‘homologous series’

Conduct the fractional distillation of crude oil

Understand and use a variety of different types of formula
used in organic chemistry
Reflecting on Organic Chemistry

What is the definition of organic chemistry?

What do you remember about organic chemistry
from IGCSE?

What is the value of learning organic chemistry?
Organic Chemistry

Organic chemistry is the chemistry of carbon
containing compounds.

From the very simple: methane

To the very complex: Haem B
Homologous Series

A homologous series is
a family of compounds
that differs only by the
length of its
hydrocarbon chain (i.e.
the number of CH2 units
in the main carbon
chain). Members are
usually listed in order of
increasing size.

Members share:

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General formula
Chemical properties
Three such series are
the:
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Alkanes
Alkenes
Alcohols
Homologous Series and Properties

What do you think will be the trend in
melting/boiling points as you go down a
homologous series?

Why?
Name
Molecular
Formula
Melting Boiling
Point
Point
C
C
State at
25C
Methane
CH4
-183
-164
gas
Ethane
C2H6
-183
-89
Propane
C3H8
-190
-42
Butane
C4H10
-138
-0.5
Pentane
C5H12
-130
36
Hexane
C6H14
-95
69
Heptane
C7H16
-91
98
Octane
C8H18
-57
125
Nonane
C9H20
-51
151
Decane
C10H22
-30
174
Undecane
C11H24
-25
196
Dodecane
C12H26
-10
216
Eicosane
C20H42
37
343
Triacontane
C30H62
66
450
liquid
solid
Fractional Distillation of Crude Oil (25 mins)

Crude oil is the main feedstock for producing organic
compounds

Complete the fractional distillation of crude oil
experiment here.

Fully explain all your observations
Formulas

Draw the compound with the formula C4H8O
What did you get?

Clearly a
molecular
formula is not
enough!
Types of Formula

Empirical Formula
C4H8O
C4H8O

Molecular Formula
C4H8O
C4H8O

Full Structural Formula

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Condensed Structural Formula
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Aka displayed formula
Note the ‘=‘ used for the C=C double bond
CH2=CHCH2CH2OH
Skeletal formula


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Not required but v. useful
Used in data booklet for complicated structures
Do not use in exam answers!
CH2=C(CH3)CH2OH
Thinking About Formulas

Produce a table to summarise each of the formulas.
Include columns for:





What they show
Pros
Cons
How you make them
Draw full structural, condensed structural and skeletal
formulas for at least 5 of the C4H8O compounds (not
the cyclic ones)
Key Points

Organic chemistry is the chemistry of carbon containing
compounds

A homologous series is a family of organic compounds
differing only by the length of their carbon chains

The melting and boiling point increases as you go down
a homologous series

Displayed formulas show the unambiguous arrangement
of atoms in a compound