Organic chemistry 1105

Organic Chemistry
The unique chemistry
of carbon


Learning objectives
Describe two reasons for abundance of carbon
compounds
Distinguish between inorganic and organic
carbon and other compounds
Distinguish between isomers and non-isomers
Describe differences between optical and
geometric isomerism
Distinguish between aromatic and nonaromatic
Identify common functional groups


One element – one branch of
chemistry
Organic compounds based on
carbon: 13 million and rising (fast)
 100,000 new compounds synthesized

annually

All 91 other elements combined:
only 300,000 compounds


Factoids about carbon
Fairly abundant in earth’s crust – but

not enough to explain domination


Highly significant to life
Key element in the human organism –
and all others


“God’s goof”:
The absence of stable mass 5
C and O are abundant because the atom with
mass 5 is unstable
Otherwise atom building after the Big Bang
would have resulted in much heavier elements
The thoughts of a cosmological atheist Fred
Hoyle:
“Some supercalculating intellect must have designed the
properties of the carbon atom, otherwise the chance of my
finding such an atom through the blind forces of nature
would be utterly minuscule….The numbers one calculates
from the facts seem to me so overwhelming as to put this
conclusion almost beyond question”


Organic and inorganic carbon
Inorganic carbon: ionic compounds
where carbon is incorporated as
carbonate – CO32Organic carbon: compounds of
carbon with itself, hydrogen and
other elements – by far the most

important


Organic carbon forms a thin canopy
Unique (?) conditions on earth that
support life
Earth’s
surface organic
Earth’s
crust inorganic


Vitalism and organic chemistry
Inorganic compounds were salts of the earth


Stable and easily synthesized

Organic compounds were of living organisms


Fragile and not easily synthesized

Belief in Vitalism posited that only living
organisms possessed a vital force necessary to
create organic compounds
In 1828 urea was synthesized and vitalism was
on the way out

Seven ages of man - many ages of a
carbon atom
 Combustion: C + O2  CO2
 Neutralization by seawater: CO2 + Ca(OH)2  CaCO3 + H2O
 Reaction with acid rain: CaCO3 + H2SO4  CO2
 Photosynthesis: CO2  Organic compounds (OC)
 Vegetation decomposes: OC  fossil fuels (FF)
 Vegetation consumed by animal: OC  new compounds
(proteins, DNA etc.)
 Respiration: sugars  CO2 + energy
 Industrialization: FF  C, CO2 + energy
 Manufacturing: FF  Plastics, polymers, drugs etc.
 Waste disposal Fossil fuels, CO2


Two reasons why carbon is unique
Carbon can form four bonds – four
valence electrons
Carbon forms very strong bonds with
itself – chains, rings etc.


Classifying organic compounds


Hydrocarbons are the simplest
organic compounds
Contain only C and H
Simplest is CH4 (natural gas)
Intermediate C8H18 (petroleum)

Synthetic polymers contain
thousands of atoms


Alkanes
All bonds are single
Saturated
No new bonds can be added
General formula CnH2n+1


Summary of types


Representing molecules
Molecular formula


Shows atoms in the molecule

Structural formula


Shows how they are all connected

Condensed structural formula


Simplified representation of connections

Naming organic compounds
Meth - ane
Number of
carbon
atoms

Type of
compound


Numbers game: count the carbon
atoms in the chain


Saturation bonding:
Multiple bonds and unsaturation
Saturated: no more bonds can be added
Unsaturated: more bonds can be formed


More reactive compounds


Alkenes contain double bonds


Going bananas:
Ethylene and fruit ripening

Examples of alkynes


Isomerism
Same number and type of atoms
Different arrangements
Hydrocarbons can have straight and branched
chains


Isomers simplified
Alkane isomers
 General formula CnH2n+1

Three isomers of pentane
 C5H12

Five isomers of hexane
 C6H14


Number of isomers mushrooms as
chain length increases
CH4 – 1 possibility
C2H6 – 1
C3H8 – 1
C4H10 – 2
C5H12 – 3
C8H18 – 18

C10H22 – 75
C20H42 – 366,319