Introduction to organic chemistry

21
21.1
21.2
21.3
21.4

1
1

Introduction to
Organic Chemistry
What is Organic Chemistry?
The Unique Nature of Carbon
Classification of Organic Compounds
Factors Affecting the Physical Properties of
Organic Compounds

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21.
1
What is
Organic
Chemistry?
2
2

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21.1 What is Organic Chemistry (SB p.2)

Organic Chemistry

3
3

•

Chemistry of the compounds present
in living organisms.

•

They all contain carbon.

•

Organic Chemistry is the Chemistry
of Carbon.

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21.1 What is Organic Chemistry (SB p.4)

Natural Sources of Organic Compounds
Living

things

Carbohydrates /
Proteins / Fats /
Vitamins /
Antibiotics

A variety of
organic products
obtained from
living things
4
4

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21.1 What is Organic Chemistry (SB p.4)

Natural Sources of Organic Compounds
Crude oil
or coal

Fractional distillation /
destructive distillation

Alkanes /
Alkenes /
Alkynes /

Aromatic
hydrocarbons
Check Point 21-1

5
5

A variety of
useful products
derived from
crude oil and coal
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21.1 What is Organic Chemistry (SB p.3)

Development of Organic Chemistry
as a Science
In the past
…,

Chemistry
Chemistry

Organic
Organic
compounds
compounds
obtained from

living organisms
6
6

Inorganic
Inorganic
compounds
compounds
obtained from
non-living sources

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21.1 What is Organic Chemistry (SB p.3)

Development of Organic Chemistry
as a Science
In 1828, Wohler (a German chemist)

(Inorganic
compound)
7
7

(Organic
compound)

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21.1 What is Organic Chemistry (SB p.3)

Development of Organic Chemistry
as a Science
Redefining … ...
Organic chemistry
chemistry is
is the
the study
study of
of carbon
carbon
Organic
compounds (except
(except CO,
CO, CO
CO22,, carbonates,
carbonates,
compounds
hydrogencarbonates, carbides
carbides and
and
hydrogencarbonates,
cyanides) obtained
obtained from
from natural
natural sources

sources or
or
cyanides)
synthesized in
in the
the laboratories.
laboratories.
synthesized

8
8

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21.
2 The Unique
Nature of
Carbon
9
9

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21.2 The Unique Nature of Carbon (SB p.5)

Ability to form four strong covalent bonds

• Electronic configuration of carbon
(ground state) : 1s22s22p2

Carbon (ground state)

10
10

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21.2 The Unique Nature of Carbon (SB p.5)

Ability to form four strong covalent bonds

• Each carbon atom has four unpaired
electrons when excited
• Tend to form four strong covalent bonds

Carbon (excited state)
11
11

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21.2 The Unique Nature of Carbon (SB p.5)

Ability to Catenate
• Carbon atoms link together to form
chains of varying length, branched
chains and rings of different sizes
• Catenation:
 Ability of atoms in forming stable
bonds with itself, hence joining up
into chains or rings
12
12

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21.2 The Unique Nature of Carbon (SB p.5)

Ability to Catenate
C – C > Si – Si > Ge – Ge > Sn – Sn
Bond strength ↓ as bond length ↑

13
13

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21.2 The Unique Nature of Carbon (SB p.5)

Ability to Catenate
C–C>N–N>O–O
Bond strength ↓
as the number of lone pairs ↑

14
14

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21.2 The Unique Nature of Carbon (SB p.5)

Ability to Catenate

15
15

CnH2n+2

n = 1,2,3,…(no limit for n)

SinH2n+2

n = 1 to 6 only → silanes

GenH2n+2

n = 1 to 3 only → germanes

SnnH2n+2

Only SnH4 (stannane) exists

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21.2 The Unique Nature of Carbon (SB p.5)

Ability to Form Multiple Bonds
sp3
sp2
sp

4σ bonds
1π bond, 3σ bonds
2π bonds, 2σ bonds

Carbon (excited state)
16
16

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21.2 The Unique Nature of Carbon (SB p.6)

Single bond

Double bond

Triple bond

* X = halogens

17
17

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21.2 The Unique Nature of Carbon (SB p.6)

Example 21-2

18
18

Check Point 21-2

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21.
3Classification

of Organic
Compounds
19
19

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21.3 Classification of Organic Compounds (SB p.7)

Functional Groups
•

20
20

Organic compounds are classified by
the the presence of characteristic
functional groups.

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21.3 Classification of Organic Compounds (SB p.7)

Functional Groups
A functional
functional group

group is
is defined
defined as
as an
an
A
atom or
or aa group
group of
of atoms
atoms that
that
atom
effectively determines
determines the
the chemical
chemical
effectively
properties of
of an
an organic
organic compound.
compound.
properties

21
21

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21.3 Classification of Organic Compounds (SB p.7)

Functional Groups

22
22

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21.3 Classification of Organic Compounds (SB p.7)

Functional Groups

23
23

•

Propane does not react with sodium

•

Ethanol and propan-1-ol react with
sodium to give hydrogen gas

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21.3 Classification of Organic Compounds (SB p.7)

Functional Groups

and

• have similar chemical properties
 they contain the same functional group –OH
 they are classified into the same
homologous series — alcohols
24
24

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21.3 Classification of Organic Compounds (SB p.12)

Homologous Series
A homologous
homologous series
series is
is aa series
series of
of
A

compounds that
that have
have the
the same
same functional
functional
compounds
group, and
and each
each member
member differs
differs from
from
group,
the next
next member
member by
by aa –– CH
CH22 –– unit
unit in
in
the
their formulae.
formulae.
their
CH4

C2 H 6
CH2

25
25

C3H8
CH2

C4H10
CH2

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