Chapter 1 (a)
An Introduction to Organic
Chemistry
BY
Mahwash Hafeez

Definitions
 The branch of Science in which we study the carbon containing compounds is called Organic Chemistry.
OR
 The study of hydrocarbons and their derivatives is called Organic Chemistry .
(because there are many compounds which contain carbon but are not regarded as organic compounds .e.g. carbon dioxide, carbon monoxide, carbides and cyanides. Most of organic compounds contain hydrogen and oxygen so named as hydrocarbons.)

Organic Compounds
 Organic compounds can be found naturally or they can be synthesized, but they all contain C and a few other elements.
 There are far more organic compounds than inorganic compounds.

History Of organic Compounds
 Initially it was thought that organic compounds need a vital force for their formation and could not be prepared in the laboratory and that their behaviour was governed by some supernatural forces. So the theory was named as VITAL
FORCE THEORY .

Synthesis of urea
 In 1828 Fredrick Wohler, a German chemist prepared the organic compound Urea by heating an aqueous solution of an inorganic compound ammonium cyanate. So the Vital
Force Theory was rejected.

Organic Compounds
 fuels
 carbohydrates, fats, proteins
 vitamins
 penicillin, sulfa drugs
 plastics
 cotton, silk, wool
 rubber
 DNA
 ibuprofen, aspirin, morphine
Organic chemistry is a part of our everyday lives!

Sources of Organic compounds
 Coal, natural gas and petroleum are the major sources of a vast variety of organic compounds.
These are called fossil fuels and are formed over a long period of time, from the decay of plants and animals.
 Natural gas is a mixture of low boiling hydrocarbons. It is used as a fuel and as a starting material for the synthetic organic reactions, for the production of hundreds of useful organic substances, such as solvents, synthetic rubber, explosives, plastics fertilizer & other industries.

Importance of organic chemistry
 1. Organic chemistry touches our lives in countless ways.
 2. It is the chemistry associated with the living matter in both plants and animals.
 3. Carbohydrates, fats, proteins , vitamins , hormones, enzymes and many drugs are organic compounds.
 4. Wood , silk , cotton , linen and such synthetic fibers as nylon, and Dacron contains organic compounds.
 5. Perfumes , dyes, flavors, soaps, detergents, plastics gasoline and oil are organic compounds.

Classification of organic compounds
SS straight chain
Branched chain straight chain
Branched chain

Properties of Organic Compounds
 usually molecular (contain non-metals bonded with covalent bonds)
 low melting points
 nonpolar (insoluble, or only slightly soluble in water)
 very stable (not reactive)

Comparison of organic compounds and in organic compounds
Property Organic inorganic
 Flammable Yes No
 Melting point
 Boiling point
 Solubility in water
 Solubility in nonpolar solvent
 Types of bonding
 Reaction occur between
 Atom per molecules
 Structure
 Electrolytes
Low
Low
No (for most)
Yes
High
High
Yes
No
Covalent Ionic
Molecules
Many
Complex
No
Ions
Few
Simpler
Yes

Bonding in organic compound
 Organic compounds – compounds of carbon are held together by covalent bond.
 Covalent bonds are formed by mutual sharing of electrons.
 Covalent bond may be single , double or triple.
 Electron configuration of carbon is (1s 2 , 2s 2 ,2p 2 ).
 Carbon has four electrons in valence shell this means that carbon can form a maximum of four covalent bonds which may be single, double or triple.
 Hydrogen can form single covalent bond only.
 Oxygen can form two covalent bonds.
 Nitrogen can form three covalent bonds.
 The bond usually is represented by a short straight line.

Single bond Double bond Triple bond
(Two electrons (Four electrons (Six electrons shared) shared) shared)

1C
2C
3C
4C
5C
Carbon Prefixes methethpropbutpent-
6C
7C
8C
9C
10C hexheptoctnondec-

Drawing organic structure
The structure of molecules determines their physical properties and the way one molecule interacts with another molecule.
Because molecules are normally too small to see, chemists have devised ways to visually represent molecules. They are as follows:
Name Molecular formula
Condensed
Formula
Structural formula
Line formula
Methane CH4 CH4
Ethane C2H6 CH3 – CH3
Propane C3H8 CH3 – CH2 – CH3

Functional Groups
 In an organic compound an atom or group of atoms denoting the chemical nature of the molecule is called a functional group.

Some important families of organic compounds & their functional groups

Isomerism
 A combination of two Greek words. i.e. Iso meaning “similar” and meros means “parts”.
 Phenomena in which compounds have the same molecular formula, but different structural formulas
 Isomers usually have different chemical and physical properties as well.
 Isomerism is of two types.

Geometrical isomerism
Geometrical isomerism is the type of stereoisomerism isomerism in which each of two or more chemical compounds have the same molecular formula but a different geometric arrangement. This type of isomerism is also called
Cis – Trans isomerism.
Example


Optical Isomerism
It is the type of stereoisomerism in which the two isomers differ only in that their molecules are mirror images of each other. The isomers are identical in molecular weight and most chemical and physical properties but differ in their effect on the rotation of polarized light. The two isomer are mirror images of each other.
Example