Chemistry Science

1. Introduction
to Organic Chemistry

2. Organic Chemistry
Organic chemistry is the study of compounds containing carbon with the exception
of simple compounds e.g. carbonates (CO3 2-), carbon dioxide (CO2) and carbon
monoxide (CO).
With the key element carbon, organic compounds contain large chemical diversity.
They contain wide variety of elements and varsity in the structures. This is due to the
unique property of carbon to form large number of compounds. This behavior of
carbon relates to:
• Its position in the periodic table.
• Its ability to form four stable covalent bonds and
• due to its relative small size which allows easy formation of multiple bonds.
Simplest organic compounds are the hydrocarbons, that is the compounds made of
carbons and hydrogen. Hydrocarbons are divided in two broad classes, Aliphatic and
Aromatic Hydrocarbons.

3. Chemical Bonding
Bonding – attractions between atoms or ions.
There are several types of chemical bonds, but we will discuss three of the strongest
types :
1. Covalent bonds
2. Metallic bonds
3. Ionic bonds
Covalent Bonds
Covalent bonds – bonds formed from atoms sharing pairs of electrons
* Molecules formed this way: CH4, H2O, O=C=O, etc …
* NO charged particles / ions involved - Sharing electrons between atoms
* Each atom “donates” one electron to the shared pair
Two atoms can share up to 3 pairs of electrons
1 shared pair = single covalent bond
2 shared pairs = double covalent bond
3 shared pairs = triple covalent bond

4. Each shared pair represented as a line in a structural formula.
Example: *H-H *C-C *C-H *O-H *N-H *C-O
**C=C **C=O *** ***
*This is a single covalent bond **This is a double covalent bond ***This is a triple
covalent bond
Metallic bonding
• Occurs between like atoms of a metal in the free state.
• Valence e- are mobile (move freely among all metal atoms).
• Positive ions in a sea of electrons.
Ionic bonding
• electrons are transferred between valence shells of atoms.
• ionic compounds are made of ions.
• ionic compounds are called Salts or Crystals.
DOUBLE bond
atoms that share two e- pairs (4 e-) O=O
TRIPLE bond
atoms that share three e- pairs (6 e-)

5. Always formed between metals and non-metals
[METALS ]+ [NON-METALS ]-
Types of Covalent Bonds
NON-Polar bonds
• Electrons shared evenly in the bond
• Electronegativity difference is zero
NaCl

6. Polar bond
Electrons unevenly shared
Electronegativity difference greater than zero but less than 2.0
closer to 2.0 more polar more “ionic character”
Place these molecules in order of increasing bond polarity
which is least and which is most?
Sometimes the bonds within a molecule are polar and yet the molecule is non-
polar because its shape is symmetrical.
Polar molecules (Dipoles) Not equal on all sides
Polar bond between 2 atoms makes a polar molecule asymmetrical shape of
molecule.

7. Melting point and boiling point
The boiling point of a substance can also be defined as the temperature at which it
can change its state from a liquid to a gas throughout the bulk of the liquid at a given
pressure. For example, the melting point of water at 1 atmosphere of pressure is 0 C
(32 F, 273.15 K; this is also known as the ice point) and the boiling point of water is
100 C.
The melting point (m.p.) is the temperature at which a solid becomes a liquid, and
the boiling point (b.p.) is the temperature at which the vapour pressure of the liquid
is equal to the atmospheric pressure.
Melting point is used to characterize organic compounds and to confirm the purity.
The melting point of a pure compound is always higher than the melting point of that
compound mixed with a small amount of an impurity. The more impurity is present,
the lower the melting point. Finally, The melting point increases as the molar mass
increases, and the boiling point increases as the molecular size increases. The
increase in melting point is less regular than the increase in boiling point, because
packing influences the melting point of a compound.

8. Polarity and solubility
Generally, there is a direct correlation between the polarity of a molecule and the
number and types of polar or nonpolar covalent bond that are present. In a few
cases, a molecule having polar bonds, but in a symmetrical arrangement, may give
rise to a nonpolar molecule, e.g. carbon dioxide (CO2).
The term bond polarity is used to describe the sharing of electrons between atoms.
In a nonpolar covalent bond, the electrons are shared equally between two atoms.
A polar covalent bond is one in which one atom has a greater attraction for the
electrons than the other atom.
Polarity is a physical property of a compound, which relates other physical
properties, e.g. melting and boiling points, solubility and intermolecular
interactions between molecules.
When this relative attraction is strong, the bond is an ionic bond. The polarity in a
bond arises from the different electronegativities of the two atoms that take part in
the bond formation. The greater the difference in electronegativity between the
bonded atoms, the greater is the polarity of the bond. For example, water is a polar
molecule, whereas cyclohexane is nonpolar.
Polarity is a physical property of a compound, which relates other physical
properties, e.g. melting and boiling points, solubility and intermolecular interactions
between molecules.

9. Solubility is the amount of a solute that can be dissolved in a specific solvent under
given conditions. The dissolved substance is called the solute and the dissolving
fluid is called the solvent, which together form a solution. The process of dissolving
is called solvation, or hydration when the solvent is water. In fact, the interaction
between a dissolved species and the molecules of a solvent is solvation.
The solubility of molecules can be explained on the basis of the polarity of
molecules. Polar, e.g. water, and nonpolar, e.g. benzene, solvents do not mix. In
general, like dissolves like; i.e., materials with similar polarity are soluble in each
other. A polar solvent, e.g. water, has partial charges that can interact with the
partial charges on a polar compound, e.g. sodium chloride (NaCl). As nonpolar
compounds have no net charge, polar solvents are not attracted to them.

10. Functional Groups
What is the family name?

11. Functional groups: are common bonding patterns found in organic
molecules. Examples:
C
C H
H
H
H
H
H
No functional group
Only carbon and hydrogen
Alkenes
Alkanes
Only carbon and hydrogen All single bonds
A carbon to carbon double bond
A carbon to carbon triple bond
Alkynes
Only carbon and hydrogen

12. Alcohols
Only one oxygen
Can classify as 1º/2º/3º according to position of O-H group on carbon skeleton
Has an O-H group
Phenols
Only one oxygen
Has an O-H group
The O-H group is directly attached to a benzene ring

13. Aldehydes
Only one oxygen
Has a C=O group
C=O group is at the end of carbon chain, so is next door to a hydrogen atom
ketones
Only one oxygen
Has a C=O group
C=O group is not at the end of carbon chain, so is next door to 2 carbons

14. This -COOH group has to be at the end of a carbon chain (why?)
Carboxylic acids
Has 2 oxygens
Has O-H and C=O groups on the same carbon atom
Esters
Has 2 oxygens
One oxygen is part of a C=O bond, the other is next door, sandwiched between two carbons

15. Ethers
Has 1 oxygen
No O-H or C=O group
The oxygen is sandwiched between two carbon atoms
Amines
Has 1 Nitrogen
The NH2 group
Amide
Has a C=O group
Has 1 Nitrogen
The C=O relative to NH2 group

16. Mercaptans
Has 1 Sulfur
SH group
Thiols
Has a C=S group
The thiol group
Nitriles
Has a group
The cynide group
Nitro compounds
Has NO2 group
The Nitro group

17. carboxylic acid
phenol
alcohol
Ketone
alkene
Multiple functional group compounds
Also we have more than one functional group in one compound, example: