1. Organic nomenclature

2. What is it?
The systematic naming of an organic compound generally requires the identification and naming of a parent structure.
This name may then be modified by prefixes, infixes, and, in the case of a parent hydride, suffixes, which give the precise structural changes required to generate the actual compound from the parent structure.

3. Naming straight-chain alkanes
Naming of straight chain alkanes (alkanes that do not branch) is a straightforward process.
To give an alkane a name, a prefix indicating the number of carbons in the molecule is added to the suffix ane, identifying both the kind of molecule (an alkane) and how many carbons the molecule has (the prefix).
The name pentane, for example, tells you that the molecule is an alkane (thus the ane ending) and that it has five carbons (pent indicates five).

4. Prefixes for alkanes that have 1-4 carbons are rooted historically.
These are methane, ethane, propane, and butane, respectively.
On the other hand, for 5 carbons and up a prefix derived from greek is given. (An easy way to remember the first four names is the anagram Mary eats peanut butter, standing for methane, ethane, propane, butane).
Learning the prefixes for up to twelve carbons is a good idea.

5. Number of Carbons
Prefix
Structure 1
Methane
CH4 2
Ethane
CH3CH3 3
Propane
CH3CH2CH3 4
Butane
CH3(CH2)2CH3 5
Pentane
CH3(CH2)3CH3 6
Hexane
CH3(CH2)4CH3 7
Heptane
CH3(CH2)5CH3 8
Octane
CH3(CH2)6CH3 9
Nonane
CH3(CH2)7CH3 10
Decane
CH3(CH2)8CH3 11
Undecane
CH3(CH2)9CH3 12
Dodecane
CH3(CH2)10CH3

6. Naming branched alkanes
The nomenclature becomes more complex if the alkane branches. In such a case, there are several rules that you must follow to give the alkane the correct name.
Find the longest chain of carbons in the molecule. The number of carbons in the longest chain becomes the parent name.
After finding the parent chain, you number the parent chain starting with the end nearest the first substituent (a substituent is any fragment that juts off the main chain).

7. Next, determine the names of all substituents
Next, determine the names of all substituents. Substituents are named as if the piece were a separate molecule, except that the suffix of yl is used rather than ane.
Thus, a two-carbon substituent would be an ethyl substituent (not an ethane substituent).
Put the substituents in alphabetical order (ie. ethyl before methyl) in front of the parent name.
Next, identify the positions of all substituents in the name by placing the carbon number where the substituent attaches to the parent chain in front of it. For example, 2-methylheptane indicates that a methyl substituent is attached to the number 2 carbon.

8. Try this one…
a)     
Which can be drawn as:

9. Step 1 Find the longest carbon chain in the molecule.
First, begin by finding the parent chain in the molecule--that is, the longest possible chain of connecting carbons.
Note that the parent chain is not necessarily the chain that simply follows from left to right.
For example, if you were to count the number of carbons directly from left to right in this molecule you would get 7 carbons. This is not the parent chain, however!
If you start at the left and then count up where the molecule branches, you find that there are 8 carbons by taking this route.
This is is the longest chain and thus the parent chain is octane.

10. Right!
8 carbon chain
Wrong!
7 carbon chain

11. Step 2 Number the parent chain.
The second step is to number the carbons in the parent chain starting at the end closest to the first substituent.
It is important to number the molecule from the correct end (in other words, in this example do you number the alkane from right to left or left to right).
Following this rule, on this molecule you number from right to left, as the 2-carbon substituent is closer to that end.

12. Right! correct numbering Wrong! incorrect numbering 1 2 3 4 6 5 7 8 8

13. Step 3 Name all the substituents.
You then identify the names of the substituents.
In this case, the only substituent is a 2 carbon group at the number 4 carbon.
This is an ethyl group. 4

14. Step 4 Put the substituents in alphabetical order.
The next step is to put the substituents in alphabetical order (ie. ethyl before methyl) but since there is only one substituent this is unnecessary.

15. Step 5
Locate the substituent on the parent change by giving it a number.
Thus, the proper nomenclature of this alkane is ethyloctane.
Note that a dash is used to separate the number from the substituent.

16. Your turn…
What is this?
And the structural formula is?
HEXANE

17. Your turn… 2-METHYL PENTANE What is this?
And the structural formula is?
2-METHYL PENTANE

18. Your turn… 3-METHYL PENTANE What is this?
And the structural formula is?
3-METHYL PENTANE

19. The prefixes di, tri, tetra etc
The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when putting the substituents in alphabetical order.
Number of same groups
Prefix 1
mono 2 di 3
tri 4
tetra

20. Your turn… 2,2-dimethylbutane What is this?
And the structural formula is?
2,2-dimethylbutane

21. Your turn… 2,3-dimethylbutane What is this?
And the structural formula is?
2,3-dimethylbutane

22. D

23. C

24. C

25. D

26. A little harder… Butanol… C4H10O What about these 4 structures?
How many C, H, O?
And what are they all called?

27. A little harder… butan-1-ol 2-methyl-propan-1-ol butan-2-ol

28. Homework… Draw and name all the possible structures with the formula:
C3H7Br (Br = bromo)
C5H12
Draw the following compounds:
3-ethyl-2,4-dimethylheptane
2,2,4-trimethylpentane
4-ethyl-3,5-dimethylheptane