In 1815 a Swedish scientist Berzelius proposed that organic compounds could only be produced by
some special force which must be existing in a living organism and could not be prepared in a
laboratory. This force was called vital force and this theory came to be known as vital force theory.
According to this theory
• The organic compounds could be extracted only from living organisms.
• They could not be prepared in a laboratory with inorganic material and they were actually
originated by a vital force [ mysterious force]
• The organic compounds did not obey the laws of chemical combination.
Vital force theory
Basic concept of organic chemistry
Limitation of vital force theory
In 1828 Friedrich Wohler, a German chemist rejected the vital force theory. Wohler synthesized an
organic compound urea by heating an inorganic compounds potassium cyanate and ammonium
sulphate.
(NH4)2 SO4 + KCNO NH4CNO + K2 SO4
Ammonium cyanate
NH4CNO NH2 CO NH2
Urea
Ammonium sulphate
potassium cyanate
Ammonium cyanate
After the synthesis of urea, many other organic compounds were synthesized in laboratory
In 1845, Kolbe synthesized acetic acid from purely inorganic compound. And in 1856, Berthelot
synthesized methane from an inorganic compound. After the synthesis of many other organic
compounds in laboratory, the classical concept of vital force theory was totally discarded
Definition of organic chemistry and organic compounds
In classical view or in 18th century , the chemical compounds were divided into two types on the basis oftheir source
Organic compounds
Inorganic compounds
• Compounds obtained from living organism were called organic compounds. Example : carbohydrates,
protein, fat, vitamins, etc
• Compounds obtained from mineral source were called inorganic compounds. Example: silicates,
limestone, etc
Modern Definition of organic chemistry and organic compounds
Organic compounds are defined as the hydrocarbons and their derivatives which contain carbon as an
essential element.
Organic compounds made of only Hydrogen and Carbon atoms only are known as hydrocarbons.
Example : methane, ethane, propane, butane, benzene, etc
All other organic compounds are considered to be derived from hydrocarbons, by replacing one or more
hydrogen atoms with atoms of other elements.
Organic chemistry is defined as the branch of chemistry that deals with the study of hydrocarbons and
their derivatives.
CH4 + Cl2 CH3 Cl + HClsunlight
CH3 Cl + Cl2 CH2 Cl2 + HClsunlight
CH2 Cl2 + Cl2 CHCl3 + HClsunlight
CHCl3 + Cl2 CCl4 + HClsunlight
CH3Cl, CH2Cl2, CHCl3, CCl4 are an example of organic compounds because they are derived from hydrocarbon
Exaples of organic compounds
Ethene
Methanol TrichloromethaneMethane
Vinyl chloride Ethyne
Reason for the separate study of organic and inorganic compoundsProperties of compounds Organic compounds Inorganic compounds
1. Number of organic compounds The total numbers of organic compounds is about 10 million
The total number of inorganic compound is only one million
2. Composition They are composed of very few elements like C, H, O, N, S, X, rarely P, Zn, As
They are composed of different elements of the periodic table
3. Nature of bond They are generally covalent in nature.Example : methane
They are generally ionic in nature. Example : NaCl
4. Solubility They are generally insoluble in water and soluble in organic solvent like CCl4, C6H6, etcException : alcohol, organic acids and carbohydrates are soluble in water due to their polar nature
They are soluble in water and insoluble in organic solvents
5. Combustibility They are generally combustible in nature. Example : methane, butane, petroleum products
They are generally non – combustible in nature
6. Functional group They contain special functional groups They do not contain functional groups
7. Isomerism They show isomerism They do not show isomerism
Classification of organic compounds
On the basis of structure, organic compounds can be broadly classifies into two
main classes.
The hydrocarbons and their derivatives which contain carbon as an essential
element are known as organic compounds
1. Open chain or Acyclic organic compounds
2. Closed chain or cyclic organic compounds
The organic compounds in which carbons atoms linked in an open chain
structure are known as open chain organic compounds. The open chains of carbons
may be straight or branched as shown below.
1. Open chain or Acyclic organic compounds:
| |
- C – C –
| |
| |
C – C–
| |
H H H H
H
HHHH
H
| |
- C – C –
| |
| |
C – C –
| |
H H H H
H
HCHH
H
H
HH
Butane
[Straight]
2-methyl butane[Branched]
CH3CH2CH2CH3
CH3
CH3-CH2-CH-CH3
Or Or
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| |
- C – C –
| |
| |
C = C–
H H H H
H
HH
H
CH3CH2CH=CH2
But-1-ene[Straight]
Or
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The open chain organic compounds are further classified into
two types as:
a. Saturated
b. Unsaturated
a. Saturated organic compounds
The organic compounds containing C-C single bond in their
molecule are known as saturated organic compounds. They have
general formula CnH2n+2 (n=No. of carbons=1,2,3,…..)
Example:
When n=1, then
C1H2x1+2=CH4
When n=2, then
C2H2x2+2=C2H6
Paraffins: Para: Without
affins: Affinity
[Do not have affinity to add more atoms]
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b. Unsaturated organic compounds
The hydrocarbon containing (C=C) double bond or (C≡C) triple bond in their
molecule are known as unsaturated organic compounds. There are two types of
unsaturated organic compounds:
Example:
When n=2, then C2H2x2=C2H4
i. Alkene [Olefins]
The hydrocarbons containing (C=C) double bond in their molecule are
known as Alkene. They have general formula CnH2n
olefins: oil forming
When n=3, then C3H2x3=C3H6
When n=4, then C4H2x4=C4H8
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| |
- C – C –
| |
| |
C = C–
H H H H
H
HH
H
CH3CH2CH=CH2
But-1-ene
Or
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Example:
When n=2, then C2H2x2-2=C2H2
ii. Alkyne
The hydrocarbons containing (C ≡ C) triple bond in their
molecule are known as Alkyne. They have general formula CnH2n-2
When n=3, then C3H2x3-2=C3H4
When n=4, then C4H2x4-2=C4H6
| |
- C – C –
| |
C ≡ C–
H H
H
HH
H
CH3-CH2-C≡ CHBut-1-yne
Or
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2. Closed chain or cyclic organic compounds:
The organic compounds which contain one or more rings of carbon atoms
are called cyclic or closed chain hydrocarbons.
These have been further divided into two categories as follows:
a) Homocyclic or carbocyclic compounds
b) Heterocyclic compounds
a) Homocyclic or carbocyclic compounds
The compounds in which the ring consists of only carbon atoms are called
homocyclic or carbocyclic compounds. These are further divided into two classes.
ii) Aromatic compoundsi) Alicyclic compounds
i) Alicyclic compounds
These compounds contain ring or closed chain carbon atoms but they resemble open chain or
aliphatic hydrocarbons in many respects. Like open chain hydrocarbons, they can be further
classified into cycloalkanes, cycloalkenes and cycloalkynes. Some examples are given below:
ii) Aromatic compounds
• The cyclic hydrocarbons with alternate C-C and C=C are called aromatic
compounds
• The name aromatic is derived from the Greek word ‘aroma’ meaning sweet
smell, because most of the compounds belonging to this class have sweet
fragrance.
• One of the earliest aromatic hydrocarbon known is benzene and hence it is
regarded as the parent aromatic hydrocarbon. For example,
Benzene Naphthalene
The cyclic compounds which consists of carbon as well as other
elements like N, O, S etc. in the ring are called heterocyclic
compounds. For example,
b) Heterocyclic compounds
Pyridine
N S
Thiophene
O
Furan
NIH
Pyrrole
Organic compounds
Open chain [acyclic] Closed chain [cyclic]
2 - Types
Saturated or alkane or paraffins
unsaturated
Alkene or olefins
Alkyne
2 – Types
2 – Types
Homocyclic Heterocyclic
Alicylic Aromatic
2 – Types
2 – Types
Functional GroupAn atom or group of atom that connected to the
carbon which determines the characteristic
properties of an organic compounds are known
as Functional group.
Example: Alcohol
R OH
Hydrocarbon part
Functional part
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Characteristics of Functional group
The function or mode of activity of an organic compound
is determined by their functional group.
An organic compounds containing same functional group
belong to the same class or family.
An organic compounds containing same functional group
will have same chemical properties.
Example: Organic compounds containing –OH as a functional group are
the members of alcohol family.
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Various functional groups and their classes are as follows:
S.N Functional Groups Name of functional group Class or family
1 -COOH Carboxy Carboxylic acid
2 -(CO)2O Acetoxy Acid anhydride
3 -COOR Alkoxy carbonyl Ester
4 -COX Halocarbonyl Acid halide
5 -CONH2 Carbamoyl Amide
6 -CN Cyano Cyanide
7 -NC Isocyano Isocyanide
8 -CHO Aldo/Formyl/oxo Aldehyde
9 -CO- Keto/Oxo Ketone
10 -OH Hydroxy Alcohol
11 -NH2 Amino Amine
12 -O- Alkoxy Ether
13 -X Halo Halo group
14 -NO2 Nitro Nitro group
15 -R Alkyl Alkyl group
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CR OH
O
1. Carboxylic Acid
Carbonyl
Hydroxy
Carbonyl + Hydroxy Carboxy
C
O
OH+C OH
O
CCH3 OH
O
CCH3 CH2 OH
O
Ethanoic acid propanoic acid
ii. Acid anhydride
CR OH
O
C+H O R
O
P2O5CR O
O
C R
O
+ H2O(RCO)2OGeneral Formula:
No water
Example
CCH3 O
O
C CH3
O
Ethanoic anhydride
iii. Ester
CR OR
O
RCOOR
C OR
O
-COOROr
General Formula:
Or
- OR
- er
Example
CCH3 OCH3
O
Methyl ethanoate
CCH3 O CH2 CH3
O
Ethyl ethanoate
iv. Acid halide
CR X
O
RCOXGeneral Formula: Or
C X
O
X = F, Cl, Br, I
HalogenHalides
Example
CCH3Cl
O
Ethanoyl chloride
CCH3Br
O
Ethanoyl bromide
iv. Amide
C NH2
O
CR NH2
O
RCONH2
General Formula:
Or
Double bond
CCH3 NH2
O
CCH3 CH2 NH2
OExample
Ethanamide Propanamide
Vi. Cyanide [Nitrile]
R-CN
General Formula:
OrC N
CR N R-CNOr
Triple bond
Example
CCH3 N CCH3 CH2 N
Ethyl cyanideMethyl cyanide
vii. Isocyanide
-NC
General Formula:
OrN C
NR C R-NCOr
Opposite of cyanide
NCH3 C
Methyl carbylamine
Example
viii. Aldehyde
OrC H
O
CHO
General Formula:
CR H
O
Or RCHO
Hydrogen
CCH3H
O
Ethanal
CCH3 CH2H
O
Propanal
Example
ix. Ketone
OrC
O
CO
General Formula: CR R
O
Or RCOR
Key
CCH3 CH3
O
Example
Acetone
6. Alcohol
OH
General Formula: R OH
Hydro + Oxy Hydroxy
CH3 OH
Methyl alcohol
Example :
CH3 – CH2 OH
Ethyl alcohol
7. Amine
NH2
General Formula: R NH2
NH2
CH3 NH2
Methyl amine
Example :
CH3 – CH2 NH2
Ethyl amine
8. Ether
O
R O R’
General Formula: R O R
Simple
R O R’
Mixed
Alkyl on either side
Ether
CH3 O CH3
Dimethyl ether
CH3 –CH2 O CH3
Ethylmethyl ether
10. Nitro group
NO2
General Formula: R NO2
Nitrogen + Oxygen Nitro
Example : CH3 NO2
Nitromethane
CH3 – CH2 - NO2Nitroethane