1. Ch. 22 Hydrocarbon Compounds

2. 22.1 Hydrocarbons Organic Chemistry
includes almost all carbon compounds
Not limited to compounds found in living cells
Hydrocarbon: organic compound made of only hydrogen and carbon atoms

3. hydrocarbons Carbon atoms have 4 valence electrons
Hydrogen atoms have 1 electron
Carbon atoms will make 4 bonds
Hydrogen atoms will only make one bond

4. Representing hydrocarbons

5. Properties of hydrocarbons
Nonpolar molecules
Will not mix with water
Mix with other nonpolar molecules
Tend to be gas or liquid (with low BP) at room temperature
Combustible in presence
of oxygen and heat

6. Alkanes Hydrocarbons with all single covalent bonds
Can be straight chain or branched chain (or ring structure)
Boiling Point and Melting Point increase with number of carbons in a straight chain compound

7. Naming straight chain alkanes
IUPAC: International Union of Pure and Applied Chemistry
Name ends with suffix –ane
Prefix indicates the number of carbon atoms
Note: the prefixes for the first 4 carbons are different than the prefixes used for inorganic compounds!

8. Drawing structural formulas
Start with the number of carbon atoms, linked by single bonds
Fill in as many hydrogen as necessary
Condensed structural
formulas can be used
to save time and space

9. Practice
Draw complete structural formulas for straight chain alkanes with
Three carbon atoms
Four carbon atoms
Seven carbon atoms
Name each of them.

10. Practice Draw the complete structural formula for Ethane Nonane
Methane

11. Practice How many single bonds are there in a propane molecule?
How many single bonds are there in a butane molecule?

12. Branched-chain Hydrocarbons
One carbon atom is bonded to 3 or 4 other carbon atoms
Branches are named as substituent groups
The longest continuous carbon chain is the parent alkane (provides number of carbons for the name prefix)
Hydrocarbon substituents are called alkyl groups
Methyl
Ethyl
Propyl
Butyl
Pentyl, etc.

16. Practice
Name this compound using the IUPAC system. *Notice that the longest chain is not written in a straight line.
3,3-dimethylhexane

17. PRactice Name the following compounds.
a) 3-ethylhexane b) 2-methylbutane c) 4-ethyl-2-methylheptane

18. Practice Draw the structural formula for 3-ethyl-2,4-dimethylhexane.
Draw the structural formula for 2,3-dimethylbutane.
Draw the structural formula for 3,4-diethyl-2,5-dimethyloctane.

19. 22.2 Unsaturated hydrocarbons
Saturated compound: contains the maximum number of hydrogen atoms per carbon atom (2n+2)
Unsaturated compound: contains at least one double or triple bond

20. Alkenes Alkene: a hydrocarbon with at least one double bond Naming
Find the longest continuous carbon chain that contains the double bond (this is the parent alkene)
Name the parent alkene by the number prefix and end in –ene
Number the parent chain so that the double bond has the lowest possible number
Any substituents are named the same as with alkanes

22. Alkynes Alkyne: a hydrocarbon with at least one triple bond Naming
Number the parent chain so that the triple bond has the lowest possible number on the longest continuous chain
Name the parent chain with the number prefix
End the name in –yne
Name substituents as with alkanes

23. Practice
Draw a complete structural formula for each of the following hydrocarbon compounds.
Ethane
Ethene
Ethyne
Propane
Propene
Propyne

24. 22.3 Isomers
Isomers have the same molecular formula but different structures
Constitutional (structural) isomers: same molecular formula but the atoms are arranged differently
Physical properties (BP, MP) differ
Chemical reactivities differ

25. stereoisomers
Stereoisomers: atoms are joined in same order, but in different arrangements in space
Cis-trans isomers
Enantiomers

26. Cis-trans isomers
Cis-trans isomers are most commonly found in compounds with double bonds (alkenes)
Cis configuration: similar groups are on the same side of the double bond
Trans configuration: similar groups are on opposite sides of the double bond

27. enantiomers
Occurs when a central atom (C) has four different atoms or groups attached
When this central atom is carbon, it is called an asymmetric carbon
Groups attached to an asymmetric carbon can form mirror images of each other
When these mirror images are not superimposable, the two forms are called enantiomers
The enantiomers have identical physical properties but can have different chemical reactions

29. Practice

30. 22.4 Hydrocarbon Rings
Cyclic Hydrocarbons

31. Aromatic hydrocarbons
Aromatic compounds contain a benzene ring
Non-aromatic compounds are called aliphatic
Benzene
Resonance increases stability
Two forms are extremes, the true bonding is an average

32. Substituted aromatic compounds
A compound with substituents added to benzene ring use benzene as the parent hydrocarbon
When the benzene ring is a substituent, it is called a phenyl group

33. Substituted aromatic compounds
With 2 substituent groups on a benzene ring numbering becomes part of the name
The different constitutional isomers have different properties

34. 22.5 Hydrocarbons from earth’s crust
Natural Gas
Source of low-mass alkanes
80% methane, 10% ethane, 4% propane, 2% butane
4% contains nitrogen, higher mass hydrocarbons, and helium
Combustion requires O2 gas
Methane burns with a hot, clean flame

35. 22.5 Hydrocarbons from earth’s crust
Petroleum
More complex compounds than in natural gas
Mostly straight or branched-chain alkanes
Includes some aromatic compounds and sulfur-, oxygen-, or nitrogen-containing compounds
Petroleum refining begins with distilling crude oil into fractions by boiling point
Cracking breaks down larger hydrocarbons into smaller, more useful hydrocarbons

37. bioremediation
Using oil-eating microbes (mostly bacteria) to clean up an oil-spill
Microbes digest crude oil into mostly CO2 and H2O
Takes time to work
Most effective along shorelines after other means of cleaning

38. 22.5 Hydrocarbons from earth’s crust
Coal
Classified by hardness and carbon content
Mostly condensed aromatic hydrocarbons with high mass
Leaves more soot when burned
Forms in multiple stages from pressure and heat over time
Peat  lignite  bituminous  anthracite