1

• Organic compounds are compounds containing carbon

• Carbon neither readily gives up nor readily accepts electrons

• Carbon shares electrons with other carbon atoms as well as with several different kinds of atoms

CH1Bonding and Isomerism

2

How Electrons are arranged in AtomThe Structure of an Atom

• An atom consists of electrons, positively charged protons,and neutral neutrons

• Electrons form chemical bonds

• Atomic number: numbers of protons in its nucleus

• Mass number: the sum of the protons and neutrons of an atom

• Isotopes have the same atomic number but different mass numbers

• The atomic weight: the average weighted mass of its atoms

• Molecular weight: the sum of the atomic weights of all the atomsin the molecule

3

How Electrons are arranged in AtomThe ground-state electronic configuration describes the orbitalsoccupied by the atom’s electrons with the lowest energy

1 | 4

Valence Electrons of the First 18 Elements

1 | 5

Ionic and Covalent bonding

6

Lewis’s theory: an atom will give up, accept, or share electrons inorder to achieve a filled outer shell or an outer shell that containseight electrons

7

Ionic Bonds Are Formed by the Transfer of Electrons

Attractive forces between opposite charges are called electrostatic attractions

8

Covalent Bonds Are Formed by Sharing Electrons

9

10

Polar Covalent Bonds

• Sharing of electrons between atoms of different electronegativities: polar covalent bond (e.g., HCl)

• Equal sharing of electrons: nonpolar covalent bond (e.g., H2, C2H6)

11

12

A polar covalent bond has a slight positive charge on one end and a slight negative charge on the other

13

14

which bond is the most polar?

1

23

F

OH NH2

4

15

Multiple Covalent Bonds

16

Writing structural formulas and Isomerism

3C + 8H gives C3H8Molecular formula

Structural formula

17

Formal Charge

Formal charge = number of valence electrons –(number of lone pair electrons +1/2 number of bonding electrons)

18

Resonance

• Only electrons can be moved (usually lone pairs or pi electrons).

• All the bond lengths are the same.• Each oxygen has a -1/3 electrical charge• The real structure is a resonance hybrid.

N

O

OO

_ _

N

O

OO

_

N

O

OO

19

Resonance Hybrid

majorcontributor

minor contributor, carbon does

not have octet=>

20

Which of the following choices dose not represent a pair of resonance forms?

A) O OH B) O O

C) NH2 NH2 D) H3C C NH2

O

H3C C NH2

O

21

Molecular Orbitals

• σ bond: formed by overlapping of two s orbitals

22

23

Important Bond Numbers

Q Which of the following pairs will have the same valance?

A) H and Cl B) C and O C) N and C D) B and F

24

Bonding in Methane

25

SP3 Hybridization of One s and Three p Orbitals

26

The orbitals used in bond formation determine the bond angles

• Tetrahedral bond angle: 109.5°

• Electron pairs spread themselves into space as far from each other as possible

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The Bonds in Ethane

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Bonding in Ethene: A Double Bond

29

Bonding in Ethyne: A Triple Bond

30

Bonding in the Methyl Cation

31

Bonding in the Methyl Radical

32

Bonding in the Methyl Anion

33

Bonding in Ammonia and in the Ammonium Ion

34

What is the hybridization of 1, 2, 3, 4, and 5?

H3C C C C

O

CH2

: ..:

1 2

3

4 5

35

How many pi bonds does the compound

shown below contain?

CC

NC CN

H

O

H

O

36

Comparison of C-H bonds:

36

Molecule Bond Energy (kcal)

Length (pm)

Ethane Csp3-H 100 110

Ethylene Csp2-H 106 108

Acetylene Csp-H 132 106

37

Comparison of C-C bonds:

37

Molecule Bond Energy (kcal)

Length (pm)

Ethane Csp3-Csp3 90 154

Ethylene Csp2-Csp2 146 133

Acetylene Csp-Csp 200 120

38

Arrange the following bonds in order of decreasing their strength ?

1

2

34

39

Summary

• The shorter the bond, the stronger it is

• The greater the electron density in the region of orbital overlap, the stronger is the bond

• The more s character, the shorter and stronger is the bond

• The more s character, the larger is the bond angle

40

The Main Functional Groups

41

Groups with a Carbon–Oxygen Double Bond (Carbonyl Groups)