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Lesson #1: Intro to organic chemistry
Organic chemistry – deals with the chemistry of carbon compounds
-
There are millions of carbon compounds
Organic molecules are the basis for life
Carbon bonds 4 times
Carbon can bond with itself and make long chains, rings, spheres, and cylinders
Carbon can make single, double and triple bonds
https://www.youtube.com/watch?v=WFacA6OwCjA
Vocabulary:
Hydrocarbon: - compounds containing only hydrogen and carbon
Carbon backbone: - the longest carbon chain in a compound
Saturated hydrocarbon: - hydrocarbon with only single bonds (i.e., the molecule contains a maximum
number of hydrogen atoms)
Ethene (unsaturated)
Note that the number of hydrogen decreases when a double bond is present.
Alkanes: - the name given to all saturated hydrocarbons
The molecular formula for any alkane is CnH2n +2 where n is the number of atoms.
Naming system for alkanes:
1. Names end in “-ane”
2. A prefix system is used to describe the number of carbons in the longest chain
3. Branches use the same prefix system but end in “-yl”
Prefix system:
1C
Meth-
2C
Eth-
3C
Prop-
4C
But-
5C
Pent-
6C
Hex-
7C
Hept-
8C
Oct-
9C
Non-
10C
Dec-
Exercises: Name the following alkanes
Molecular Formula: C10H22
Structural diagram: Below
C
C
-C–C–C–C–C–C–C–
C
Note: the hydrogens have been removed to simplify the
diagram.
Step 1. Identify the longest continuous carbon chain.
C
C
-C–C–C–C–C–C–C–
8C would be named octane.
C
Step 2. Choose the smallest possible numbering system on the carbon backbone to locate the
branches. In this case 3&6 are the lowest numbers regardless of whether we count left to
right or right to left.
Step 3. Name the branches in alphabetical order ending in “-yl” and include the carbon number
where they are located.
3,6 – dimethyloctane.
Note that the prefix “di” is used to indicate the presence of two
“methyl” branches.
Name: C5H12
-C–C–C–C
C
The longest chain is 5C. Therefore this is pentane.
Name: C5H12
C
-C–C–C–
C
The longest chain is 3C, therefore the carbon backbone is called propane.
There are two methyl branches on the #2 carbon, therefore 2,2 – dimethyl
2,2 – dimethylpropane. (While this question and the previous one have the same molecular
formula, the structural diagram is different. These structural differences when the formulas are
the same are called structural isomers).
Name:
C
C
C
-C–C–C–C–C–C–C–
C
C
C
C
C
The carbon backbone is 8C, therefore this is a type of octane.
The smallest numbering system is from right to left.
4-ethyl-3,5-dimethly-5-propyloctane (note that the prefixes used for indicating the
number of branches is not used to determine the alpha order for naming)
Draw the following molecules:
3-ethyl-2methylpentane
Step #1: Draw the carbon backbone
C–C–C–C–C
or
H3C
CH3
Step #2: Number the carbons from left to right and attach the branches.
C
C–C–C–C–C
C
C
CH3
H3C
or
CH3
H3C
Question: Does it matter whether the branches point up or down?
Answer: No. Single bonds “spin” so the orientation of the branches is not fixed.
Draw: 4-ethyl-2,4-dimethylheptane
H3C
Step #1: Draw heptane
Step #2: Add branches
CH3
H3C
CH3
CH3
CH3
Assignment: Hebden pg. 221 #8 and 9
CH3