1. The unique chemistry of carbon
Organic Chemistry
The unique chemistry of carbon

2. 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 non-aromatic
Identify common functional groups

3. 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

4. Factoids about carbon
Fairly abundant in earth’s crust – but not enough to explain domination

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

6. “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”

7. 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

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

9. 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

10. 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

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

12. Classifying organic compounds

13. 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

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

15. Summary of types

16. Representing molecules
Molecular formula
Shows atoms in the molecule
Structural formula
Shows how they are all connected
Condensed structural formula
Simplified representation of connections

17. Naming organic compounds
Meth - ane
Number of carbon atoms
Type of compound

18. Numbers game: count the carbon atoms in the chain

19. Saturation bonding: Multiple bonds and unsaturation
Saturated: no more bonds can be added
Unsaturated: more bonds can be formed
More reactive compounds

20. Alkenes contain double bonds

21. Going bananas: Ethylene and fruit ripening

22. Examples of alkynes

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

24. Isomers simplified Alkane isomers Three isomers of pentane
General formula CnH2n+1
Three isomers of pentane
C5H12
Five isomers of hexane
C6H14

25. 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

26. Optical isomerism is a special variation
Molecules exhibit handedness – mirror images which are not super-imposable
Must have tetrahedral carbon with four different groups attached
This carbon is chiral

27. Isomers and reaction yield
Each chiral carbon produces two isomers
If there are n chiral carbon atoms there are 2n isomers

28. 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

29. 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

30. Aromatic: the stuff of dreams
Benzene ring contains 6 C atoms
Bonding is resonant – more stable than expected
All aromatic compounds contain at least one benzene ring
Benzene, C6H6, is one of the most important industrial chemicals

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

32. Functional groups
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

33. Heteroatoms affect physical and chemical properties
C2H6 (ethane) is a gas at RT
C2H6 is insoluble in water
C2H6O (ethanol) is a liquid at RT
C2H6O is soluble in water
Differences in cohesive forces: O-H bonds are polar, C-H bonds are not

34. Functionalized hydrocarbons

35. Chlorocarbons and the environment
Important uses – important problems
Solvents CH2Cl2
Insecticides DDT
Refrigerants CFCs

36. Alcohols: hic Functional group –OH Polar molecules dissolve in H2O
Ethanol: good for your health/bad for your health?

37. 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

38. Ketones Ketone is R1R2CO Acetone is a common solvent
Smell found in cinnamon
Raspberries

39. Carboxylic acids Commonly found in citrus fruits and any sour foods
Formic acid present in ant and bee stings

40. Esters: sweet aromas and flavours
Ester group is R1COOR2
Sweet aroma in pineapples, jasmine
Synthetic versions are very common

41. Ethers Ethers contain R1-O-R2 No -OH bonds Not soluble in water
Anesthetics

42. Amines: the stench of death
Amines contain NR1R2R3
Rotting fish
Decaying flesh
Illicit drugs