1. Organic Compounds - Alkanes
Dr. Sean Bonness
Chemistry Department
El Camino College

2. Organic compounds All contain carbon.
Organic chemistry is the study of carbon containing compounds.
The essential needs of daily human life are food, fuel, shelter, and clothing - all are organic in nature, except water (H2O).

3. Bonding characteristics and Isomerism
What is the electronic configuration of Carbon
Mixing of the 2s and 2p orbitals for carbon produce sp3 hybrid orbitals
The hybrid orbitals point towards the corners of a regular tetrahedron. For example methane (CH4).

4. Bonding characteristics and Isomerism (Cont.)
Carbon atoms bond covalently to other carbon atoms to form chains or networks.
A third carbon can join the end of this chain.
The process can continue to form chains of almost any length.

5. Bonding characteristics and Isomerism (Cont.)
Carbon can also share more than on pair of electrons to form multiple bonds
Structural Isomers - compounds that have the same molecular formula but in which the atoms bond in different patterns.
For example, what are the isomers for the compound with molecular formula C4H10?

6. Bonding characteristics and Isomerism (Cont.)
What are the structural isomers of C2H6O?
Structural isomers exert a significant influence on properties. Ethyl alcohol is a liquid at room temp., whereas dimethyl ether is a gas.
What is a structural isomer of C3H6O?

7. Functional groups class Functionalgroup Expanded structure
Condensed structure
Name
Alkane
Alkene
Alkyne

8. Functional groups (cont.)
class
Functionalgroup
Expanded structure
Condensed structure
Name
Aromatic
Alcohol
Ether

9. Functional groups (cont.)
class
Functionalgroup
Expanded structure
Condensed structure
Name
Amine
Aldehyde
Ketone

10. Functional groups (cont.)
class
Functionalgroup
Expanded structure
Condensed structure
Name
Carboxylic Acid
Ester
Amide

11. Functional Groups (cont.)
Write condensed structural formulas for the following compounds.

12. Alkane structures
Hydrocarbons - simplest of all organic compounds. Only contain Carbon and Hydrogen.
Are called Saturated Hydrocarbons.
Unsaturated hydrocarbons have double and triple bonds. Which of the functional groups are unsaturated?
We also have normal alkanes and branched alkanes, i.e. butane.

13. Conformations of alkanes
Conformations are the different arrangements of atoms in space achieved by rotation about a single bond.
Butane
Ethane
Are these pairs structural isomers?

14. Alkane Nomenclature Assigning IUPAC names.
Step 1 - name longest chain.
Step 2 - number the longest chain
Step 3 - locate and name attached alkyl groups.
Step 4 - combine longest chain and alkyl groups into name

15. Alkane Nomenclature (cont.)
Step 5 - indicate the number and position of attached alkyl groups. If two or more alkyl groups, then use prefixes di, tri, tetra, etc.

16. Cycloalkanes For alkanes the structural formula is CnH2n+2
Is C3H6 an alkane?
If form a ring than
And has the structural formula

17. Cycloalkanes Name Structural formula Condensed formula cyclopropane
cyclobutane
cyclopentane
cyclohexane

18. Shapes of cycloalkanes
Stereoisomers are compounds with the same structural formula but different spatial arrangements of atoms.
For example 1,2-dimethylcyclopentane
Geometric isomers are stereoisomers in which the geometry of their groups are maintained by rings and are called cis-trans isomers.

19. Shapes of cycloalkanes (cont.)
Show geometric isomers for 1,2-dimethylcyclobutane
What are the geometric isomers for 1,3-difluorocyclobutane?

20. Physical properties of alkanes
Alkanes are composed of nonpolar carbon-carbon and carbon-hydrogen bonds.
Have lower melting points and boiling points than other organic compounds due to weak attractions. However as chain length increases, the dispersion forces increases and which is why very long chain structures are solids (see figure in S&S text)