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

@Puspa Joshi

| |

- 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