
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

 Fairly abundant in earth’s crust – but not enough to explain domination


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”

 Inorganic carbon: ionic compounds where carbon is incorporated as carbonate – CO
3
2-

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


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 + O
2

CO
2
 Neutralization by seawater: CO

Reaction with acid rain: CaCO

Photosynthesis: CO
2
3
2
+ Ca(OH)
+ H
2
SO
4
2

CaCO
3

CO
2

Organic compounds (OC)

Vegetation decomposes: OC
 fossil fuels (FF)
+ H

Vegetation consumed by animal: OC
 new compounds
2
O
(proteins, DNA etc.)

Respiration: sugars

CO
2
+ energy

Industrialization: FF

C, CO
2
+ energy
 Manufacturing: FF

Plastics, polymers, drugs etc.

Waste disposal

Fossil fuels, CO
2

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

Hydrocarbons are the simplest organic compounds
 Contain only C and H

Simplest is CH
4
(natural gas)

Intermediate C
8
H
18
(petroleum)

Synthetic polymers contain thousands of atoms

 All bonds are single

Saturated

No new bonds can be added

General formula C n
H
2n+1


Molecular formula
 Shows atoms in the molecule

Structural formula
 Shows how they are all connected

Condensed structural formula
 Simplified representation of connections

 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

Going bananas:
Ethylene and fruit ripening

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

 Alkane isomers
 General formula C n
H
2n+1

Three isomers of pentane
 C
5
H
12

Five isomers of hexane
 C
6
H
14


CH
4

C

C
3
2
H
6
– 1 possibility
– 1

C
4
H
8

C
5
H
10
– 1
– 2

C
8

C
10
H
12
H
18

C
20
H
22
H
42
– 3
– 18
– 75
– 366,319

Optical isomerism is a special variation
 Molecules exhibit handedness – mirror images which are not superimposable

Must have tetrahedral carbon with four different groups attached

This carbon is chiral

 Each chiral carbon produces two isomers

If there are n chiral carbon atoms there are 2 n isomers

Optical isomers are important in nature

Amino acids are building blocks of proteins

Amino acids are chiral

Proteins contain hundreds – thousands of amino acids

Getting the correct isomer is a big deal

Geometric isomers:
Isomerism and a healthy diet
 What’s with all this trans fats anyway?

Ask a Chicago Alderman

Different geometry - same attachments

Cis isomers:

Don’t pack together
 Cis isomers have low viscosity - good

Trans isomers:
 Pack together tightly
 Trans isomers are solids - bad


Benzene ring contains 6 C atoms
 Bonding is resonant – more stable than expected

All aromatic compounds contain at least one benzene ring

Benzene, C
6
H
6
, is one of the most important industrial chemicals

 Benzene is regarded as a highly carcinogenic substance

Use and disposal of benzene are regulated

Compounds containing benzene rings are not necessarily toxic

 Chemistry of organic compounds is determined by functional groups

Functional group is an atom or group of atoms that are different from C

Heteroatoms confer very different properties on the substance

Heteroatoms affect physical and chemical properties
 C
2
H
6

C
2
H
6
(ethane) is a gas at RT is insoluble in water

C
2
H
6
O (ethanol) is a liquid at RT

C
2
H
6
O is soluble in water
 Differences in cohesive forces: O-H bonds are polar, C-H bonds are not

Chlorocarbons and the environment
 Important uses – important problems
 Solvents CH
2
Cl
2
 Insecticides DDT
 Refrigerants CFCs

 Functional group –OH

Polar molecules dissolve in H
2
O

Ethanol: good for your health/bad for your health?

Smoke gets in my eyes: olefactory pleasures of aldehydes
 C=O is carbonyl group

Aldehyde contains RCHO

Formaldehyde is a preservative and a product of burning wood

Acrolein is a product of barbequing

Common smells and flavours

 Ketone is R
1
R
2
CO

Acetone is a common solvent

Smell found in cinnamon

Raspberries

 Commonly found in citrus fruits and any sour foods

Formic acid present in ant and bee stings

Esters: sweet aromas and flavours
 Ester group is R
1
COOR
2

Sweet aroma in pineapples, jasmine

Synthetic versions are very common

 Ethers contain R
1
-O-R
2

No -OH bonds

Not soluble in water

Anesthetics

 Amines contain NR
1
R
2
R
3

Rotting fish

Decaying flesh

Illicit drugs