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Organic Chemistry

Introduction

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Atomic number :- number of proton inside nucleus or number of

electrons surrounding nucleus.

Mass number :- total number of protons and neutrons in an atomic

nucleus.

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Covalent Bonds

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Type of Hybridization

Number of sigma bond :

4 = SP3

3 = SP2

2 = SP

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Characterization of SP3 Hybridization

1- Shape :- Tetrahedral "Pyramidal"

2- Bond Angle :- 109.5o

3- Bond Length :- 1.5 Ao

4- S Character :- 25%

5- P Character :- 75%

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Characterization of SP2 Hybridization

1-Shape :- Trigonal "Planar "

2- Bond Angle :- 120o

3- Bond Length :- 1.3Ao

4- S Character :- 33.3 %

6- P Character :- 66.7 %

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Characterization of SP Hybridization

1- Shape :- Linear

2- Bond Angle :- 180o

3- Bond Length :- 1.2 Ao

4- S Character :- 50%

5- P Character :- 50%

We make a table for Hybridization types

Hybridization SP3

SP2

SP

Shape Tetrahedral

"Pyramidal"

Trigonal Linear

Bond Angle 109.5o 120

o 180

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Bond Length 1.5Ao 1.3A

o 1.2A

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Example Methane (CH4) Ethylene (C2H6) Acetylene (C2H2)

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Distinguish between sigma bond and pi bond

Sigma Bond(δ) Pi Bond(π)

Formed by linear overlap Formed by lateral overlap

Strong bond Weak bond

Formed in :-

1- 2- 2 Hybrid orbitals ex: ethane

3- Hybrid orbital + S ex: methane

Formed in :-

Not Hybrid orbitals

Has independent existence Has dependent existence

Free rotation Restricted rotation

Type of Hybridization

Number of "Sigma bonds + Ione pair of electrone

All halogens possess three lone pair

Ex1:- water molecule (H2O)

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Non – bonding orbital : Orbital contain lone pair of electrons.

Ex 2 :- ammonia molecule (NH3)

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Determine Type of Hybridization

Definitions

Organic Chemistry :- It is the chemistry of carbon and

hydrogen

Valence :- It is the number of electrons a needed to fill the

valence shell of atom.

Octet Rule :- The outer most shell ( valence shell) must be

filled with eight electrons.

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Hybridization :- It is the mixing of orbitals in valence shell to

form hybrid orbitals have identical shape and same bond angle

and same energy.

Atoms have lone pair of electrons :

1- Hetero atoms

2- Halogens

F , Cl , Br , I = have three lone pair

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Hybridization of ions

Carbcation C+

Carboanion C-

Free radical C.

Types of fission "Cleavage"

Heterolytic Fission

From carbocation C+ and Carboanion C

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Homolytic Fission

From carbo Radical C.

Hybridization of ions

Carbcation C+ No Hybridization

Carboanion C- yes Hybridization

Free radical C. No Hybridization

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Negative charge Calculate in hybridization except in states the

following :-

Atom that contain one lone pair of electron or negative charge

and all bond its single and connected with atom it has

hybridization SP2 or SP will no calculated lone pair of electron

and no negative charge.

Atom that contain two lone pair of electrons and all bond its single

and connected with atom it has hybridization SP2 or SP will

calculated only one lone pair of electron.

Atom that contain one or two lone pair of electrons but from

double bond . calculate all lone pair of electrons.

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Inductive – mesomeric effect

mesomeric effect

Complete transfer of electrons through Pi bond " double , triple bond"

Bond order :- Is the number of chemical bonds between a pair of atom.

As the bond order increase the bond will stronger and shorter

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Valence and bonding in organic compounds

Table : Valence of common elements

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Polarity of Bonds :- depends on the electronegativity difference of the

atoms formic this bond .

Table :- Electronegativity of some common elements

I II III IV V VI VII

H Be B C N O F

Li Mg Al Si P S Cl

Na Ca Br

K I

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Arrows

Straight arrow

Pair of straight arrow with half head

Is used to indicate the equilibrium reaction

Double headed straight arrow

Is used to indicate the Resonance

Curved arrow

Is used to indicate the movement a pair from electrons

Fish hock arrow

Is used to indicate the movement one from electrons