Biological ChemistryFIRST YEAR ORGANIC CHEMISTRY

Lecture OneIntroduction, Nomenclature,

Bonding

Convenor : Dr. Fawaz Aldabbagh

What is Organic Chemistry?

It is defined as the study of hydrocarbons (compounds of hydrogen and carbon) and

their derivatives

7 million Organic Compounds1.5 million Inorganic Compounds

Animal and plant matter, Foods, Pharmaceuticals, Cosmetics, Fertilizers, Plastics, Petrochemicals, Clothing

CarbonWhy is it the element of life on earth?

Has Four Bonding Electrons

Unique Strong Covalent Bonds

Strong Single, Double and Triple Bonds

Average Bond Energies (KJ mol-1)

C-C 607 Si-Si 230 C-H 416 Si-H 323

C-N 754 Si-N 470 C-O 336 Si-O 368

O-Si-O = Sand and Rocks

H

CH H

H

methane

Carbon has 4 valence electrons

C

H

H

H

H

H C

Ne

Neon

Stable Octet required

Simplest Organic molecule

Covalent Bonding – Atoms Share Electrons

Ionic Bonding – transfer of one or more electrons from one atom to another to create ions

Ionic Compound = LiF

Li (3) - 1s2, 2s1

Li+ - 1s2, 2s0

F (9) - 1s2, 2s2, 2px2, 2py

2, 2pz1

F- - 1s2, 2s2, 2px2, 2py

2, 2pz2

Ionic Compound = MgCl2

Mg (12) - 1s2, 2s2, 2p6, 3s2 Mg2+ - 1s2, 2s2, 2p6, 3s0

Cl- - 1s2, 2s2, 2p6, 2s2, 2p6

Cl- - 1s2, 2s2, 2p6, 2s2, 2p6Cl (17) - 1s2, 2s2, 2p6, 3s2, 3p5

- 2 e

+ 2 e

C(6) - 1s2, 2s2, 2px1, 2py

1, 2pz0

lowest energy state

Hybridization

C(6) - 1s2, 2s1, 2px1, 2py

1, 2pz1

Excited state 4 sp3

2s 2px2py 2pz

+ + +

4 X sp3

Methane is Tetrahedral

109.50

Sp3 hybridized carbon 4 equivalent C-H bonds (bonds)

All purely single bonds are called bonds

H

CH

HH

Alkanes

C C

H H

HHH

H

Ethane

Rotation of groups joinedby single bonds does notusually require lots of energy

H

CH H

H

methane

H

CH C

H

ethane

H

H

H

CH4 C2H6

H

CH C

H

H

C

H

H

H

H

propaneC3H8

CH4 CH3CH3 CH3CH2CH3

CnH2n+2

IUPAC-NomenclatureThe ending of all names of

alkanes is ane – remove H = alkyl

H3C H H3C methyl

CH3CH2 H CH3CH2 ethyl

CH3CH2CH2 H CH3CH2CH2 propyl

CH3CH2CH2CH2 H CH3CH2CH2CH2 butyl

3D – models show that because of the tetrahedral carbon atoms the chains are

zig-zagged and not at all straight

propyl butylRR

Constitutional Isomers

H3C C

CH3

CH3

H

Isobutane

H3C CH

CH3

CH2 CH3

Isopentane

H3C C

CH3

CH3

CH3

Neopentane

Has the same molecular formula as butane, C4H10

Has the same molecular formula as pentane, C5H12

Have different PhysicalProperties, Mpt, Bpt, densities, indexes of

refraction etc

Naming Compounds

H3C C CH2

CH3

CH3

C

CH3

CH3

CH3

2-methylhexane

2-propylheptane 4-ethyl-3-methylhexane

2,3,5-trimethylhexane

2,2,4,4-tetramethylpentane

4-tert-butyloctane or

4-(1,1-dimethylethyl)octane

C1-C4 AlkanesMethane - origins of life. Atmosphere of Jupiter, Saturn,Uranus and Neptune. Marsh Gas, Cow’s stomach. CoalMines and Natural Gas.Unprocessed Natural Gas contains 50-90% methane, 1-10% ethane and up to 8% propane and butane.Methane and Ethane are handled as compressed GasesPropane and Butane are stored in low pressure cylindersIn liquified forms (Bottled Gas).All are Colourless, odourless gases, non-toxic – Danger in inhaling lies in potential suffocation due to a lack ofOxygen or Explosions when mixed with air.

CH4 2 O2+ CO2 + 2 H2O

Combustion

+ Energy