In 1828, a German chemist Friedrich Wöhler (1800-1882) amazed the sience

community by using the inorganic compound ammonium cyanate to synthesize

urea, an organic substance found in the urine of many animals.

Organism

Organic Chemistry

Prior to 1828, all organic compounds had been obtained from organisms or their

remains. The scientific philosophy back then was that the synthesis of organic

compounds could only be produced within living matter while inorganic compounds

were synthesized from non-living matter. A theory known as "Vitalism" stated that a

"vital force" from living organisms was necessary to make an organic compound.

Vital Force

Today, chemists consider organic compounds to be those containing carbon and

one or more other elements, most often hydrogen, oxygen, nitrogen, sulfur, or the

halogens, but sometimes others as well. Organic chemistry is defined as the

chemistry of carbon and its compounds.

Modern Definition

Why CARBON

There are more carbon compounds than there are compounds of all other

elements combined. The great number of carbon compounds is possible because

of the ability of carbon to form strong covalent bonds to each other while also

holding the atoms of other nonmetals strongly. Carbon atoms have the special

property to bond with each other to form chains, ring, spheres, and tubes. Chains

of carbon atoms can be thousands of atoms long, as in polyethylene.

Electronic Structure of Carbon

1s22s22px12py

1

1s

2s

2px 2py

EN

ER

GY

Hybridization and Bonding

2s

2px 2py 2pz

Promotion

2s

2px 2py 2pz

sp3 hybrid orbitals

Carbon-Carbon Bond Formation

sp3

sp3sp3

sp3

sp3

sp3

sp3

sp3

sp3

sp3sp3

sp3

sp3

sp3

sp3

sp3

-bond

C-C

C=C

pure p

sp2

sp2

sp2sp2sp2

sp2

pure p

sp2

sp2

sp2sp2sp2

sp2

-bond

-bond

-bond

spsp

pp

pp

spsp

pp

pp

spsp

pp

pp

spsp

pp

pp

-bond

-bond

-bond

-bond

-bond

CC

Important Rules

Aufbau (Building-up) Principle

The orbitals of lower energy are filled in first with the

electrons and only then the orbitals of high energy are filled

atoms tend to combine in such a way that they each have

eight electrons in their valence shells, giving them the same

electronic configuration as a noble gas

Octate Rule

Atoms other than Carbon

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18group

period

1

2

3

4

5

6

7

H

B C N O F Ne

He

Al Si P S Cl Ar

Se Br

I

Kr

Xe

ORGANIC CHEMISTRY INPERIODIC TABLE

Electronic Configuration

1s 2s 2p 3s 3p

H

B

C

N

O

F

Al

Si

P

S

Cl

3d

Bonding Prediction

C

O

1s 2s 2psp2 hybrids

p

sp2 hybridsp

pure p

..pure p

sp2sp2

-bond

-bond

-bond..

....

H

H

C O OCH

H

....

Bond Order

1A 2A 3A 4A 5A 6A 7A 8A

1 2

H

1s1

He

1s2

3 4 5 6 7 8 9 10

Li

1s2

2s1

Be

1s2

2s2

B

1s2

2s22p1

C

1s2

2s22p2

N

1s2

2s22p3

O

1s2

2s22p4

F

1s2

2s22p5

Ne

1s2

2s22p6

11 12 13 14 15 16 17 18

Na

[Ne]

3s1

Mg

[Ne]

3s2

Al

[Ne]

3s23p1

Si

[Ne]

3s23p2

P

[Ne]

3s23p3

S

[Ne]

3s23p4

Cl

[Ne]

3s23p5

Ar

[Ne]

3s23p6

Electronic configurations

Valence Shell and Valence Electron

The highest occupied electron shell is called the valence shell, and the electrons occupying this shell are called valence electrons

The halogens (F, Cl, Br etc.) are one electron short of a valence shell octet, and are among

the most reactive of the elements. In their chemical reactions halogen atoms achieve a

valence shell octet by capturing or borrowing the eighth electron from another atom or

molecule. The alkali metals Li, Na, K etc are also exceptionally reactive, but for the opposite

reason

Valence

The number of valence shell electrons an atom must gain or lose to achieve a valence octet is called valence. In covalent compounds the number of bonds which are characteristically formed by a given atom is equal to that atom's valence.

Atom H C N O F Cl Br I

Valence 1 4 3 2 1 1 1 1

Bonding

Ionic BondingWhen sodium is burned in a chlorine atmosphere, it produces the compound sodium chloride. This has a high melting point (800 ºC) and dissolves in water to give a conducting solution. Sodium chloride is an ionic compound. Transfer of the lone 3s electron of a sodium atom to the half-filled 3p orbital of a chlorine atom generates a sodium cation (neon valence shell) and a chloride anion (argon valence shell). Electrostatic attraction results in these oppositely charged ions packing together in a lattice. The attractive forces holding the ions in place can be referred to as ionic bonds

Covalent Bonding

Covalent bonding occurs by a sharing of valence electrons, rather than an outright electron transfer. Similarities in physical properties (they are all gases) suggest that the diatomic elements H2, N2, O2, F2 & Cl2 also have covalent bonds

Double covalent bonding

Common Name Molecular Formula Lewis Formula Kekulé Formula

Methane CH4

AmmoniaNH3

Ethane C2H6

Methyl Alcohol CH4O

Ethylene C2H4

Formaldehyde CH2O

Acetylene C2H2

Hydrogen Cyanide CHN

Lewis and Kekule formula

Electronegativity

The ability of an element to attract or hold onto electrons is called

electronegativity

H

2.20Electronegativity Values for Some Elements

Li

0.98

Be

1.57

B

2.04

C

2.55

N

3.04

O

3.44

F

3.98

Na

0.90

Mg

1.31

Al

1.61

Si

1.90

P

2.19

S

2.58

Cl

3.16

K

0.82

Ca

1.00

Ga

1.81

Ge

2.01

As

2.18

Se

2.55

Br

2.96

CC : HC : ClC :+− + −

Covalent

bond Polar Covalent bond

Dipole Moment

O

HH

CClCl Cl

Cl

CClCl H

Cl

Effect of Electronegativity

Acidity of the molecule

CHH H

HO

HH H F

Essentiallynon-acidic

1025 more acidic

than CH4

1012 more acidic

than H2O

Electronegativity difference transmitted through connecting covalent bonds

by Inductive effect

CH3C OH

H

H

CF3C OH

H

H

103 times more acidic

than ethanol

Charge Distribution

If the electron pairs in covalent bonds were donated and shared absolutely evenly there would be no fixed local charges within a molecule. Although this is true for diatomic elements such as H2, N2 and O2, most covalent compounds show some degree of local charge separation, resulting in bond and / or molecular dipoles. A dipole exists when the centers of positive and negative charge distribution do not coincide

•In the formula for ozone the central oxygen atom has three bonds and a full positive charge while the right hand oxygen has a single bond and is negatively charged. The overall charge of the ozone molecule is therefore zero.

•Similarly, nitromethane has a positive-charged nitrogen and a negative-charged oxygen, the total molecular charge again being zero.

•Finally, azide anion has two negative-charged nitrogens and one positive-charged nitrogen, the total charge being minus one.

Which compounds (A through L) have no polar covalent bonds?

Which compounds have polar single bonds to hydrogen?

Which compounds have polar single bonds to carbon?

Which compounds have polar double bonds?

Which compounds have polar triple bonds?